Xi Bei Ta

Symptomatic treatment of asthma attacks and exacerbations of asthma in adults and children aged 4 years and over. Prevention of exercise-induced bronchospasm or before exposure to a known unavoidable allergen challenge. Symptomatic treatment of broncho-asthma and other conditions associated with reversible airways obstruction.

Salbutamol provides a short-acting bronchodilation with fast onset of action in reversible airways obstruction due to asthma.

Easyhaler Salbutamol Sulfate should be used to relieve symptoms when they occur and to prevent them in those circumstances recognised by the patient to precipitate an attack (e.g. before exercise or unavoidable allergen exposure).

Salbutamol is valuable as a rescue medication in mild, moderate or severe asthma, provided that reliance on it does not delay the introduction and use of regular inhaled corticosteroid therapy.

Easyhaler Salbutamol Sulfate is indicated in adults, adolescents and children aged 4 to 11 years.

Symptomatic treatment of asthma attacks and exacerbations of asthma in adults and children aged 4 years and over. Prevention of exercise-induced bronchospasm or before exposure to a known unavoidable allergen challenge. Symptomatic treatment of broncho-asthma and other conditions associated with reversible airways obstruction.

Xi Bei Ta provides a short-acting bronchodilation with fast onset of action in reversible airways obstruction due to asthma.

Easyhaler Xi Bei Ta Sulfate should be used to relieve symptoms when they occur and to prevent them in those circumstances recognised by the patient to precipitate an attack (e.g. before exercise or unavoidable allergen exposure).

Xi Bei Ta is valuable as a rescue medication in mild, moderate or severe asthma, provided that reliance on it does not delay the introduction and use of regular inhaled corticosteroid therapy.

Easyhaler Xi Bei Ta Sulfate is indicated in adults, adolescents and children aged 4 to 11 years.

Xi Bei Ta are indicated in adults, adolescents and children aged 4 to 11 years.

Salbutamol is a selective β2-agonist providing short-acting (4-6 hour) bronchodilation with a fast onset (within 5 minutes) in reversible airways obstruction.

Xi Bei Ta are indicated for use in the routine management of chronic bronchospasm unresponsive to conventional therapy, and in the treatment of acute severe asthma.

Posology

Adults and Older people:

For the relief of acute bronchospasm and for managing intermittent episodes of asthma, one inhalation (100 micrograms) may be administered as a single starting dose; this may be increased to two inhalations (200 micrograms) if necessary.

To prevent exercise-induced bronchospasm or allergen bronchospasm two inhalations (200 micrograms) should be taken before challenge, this dose (200 micrograms) may be repeated if necessary.

Paediatric Population:

Relief of acute bronchospasm

Children aged 4 to 11 years 100 micrograms as required. The dose may be increased to two inhalations if required.

Children aged 12 years and over: Dose as per adult population.

Prevention of allergen or exercise-induced bronchospasm

Children aged 4 to 11 years 100 micrograms before challenge or exertion. The dose may be increased to two inhalations if required.

Children aged 12 years and over: Dose as per adult population.

Chronic therapy

Children aged 4 to 11 years up to 200 micrograms four times a day.

On-demand use of Easyhaler Salbutamol Sulfate should not exceed four times daily. Reliance on such frequent supplementary use, or a sudden increase in dose, indicates poorly controlled or deteriorating asthma.

Children aged 12 years and over: Dose as per adult population.

On demand use of Easyhaler Salbutamol Sulfate should not exceed eight inhalations (800 micrograms) in any 24 hour period.

For optimum results in most patients Easyhaler Salbutamol Sulfate inhaler should be used regularly during asthmatic attacks. The bronchodilator effect of each administration of inhaled salbutamol lasts for four hours, except in patients whose asthma is becoming worse. Such patients should be warned not to increase their usage of salbutamol, but should seek medical advice in case treatment with an inhaled and/or systemic glucocorticosteroid is indicated.

Method of administration

For oral inhalation only.

This preparation is particularly useful for patients unable to use metered dose inhalers properly and for patients in whom the use of an inhalation aerosol causes irritation of airways. Inhaled salbutamol should be used only on as-needed basis at the lowest dose and frequency required.

Precautions to be taken before handling or administering the medicinal product

Instructions for use:

The protective cover of the inhaler should be opened and the dust cap removed immediately prior to use.

The inhaler should be shaken vigorously up and down 3-5 times. Whilst holding the inhaler in an upright position, between the finger and thumb, press once until a click is heard. Let inhaler click back again whilst continuing to hold in an upright position.

Inhalation should take place from either a sitting or standing position. The patient should breathe out normally and place the mouthpiece between their teeth whilst using their lips to form a seal around the mouthpiece. Patients are instructed to perform a rapid and forced inhalation through the Easyhaler device. After holding their breath for at least 5 seconds the patient can resume normal breathing. Patients should not to exhale into the device.

The mouthpiece of the inhaler should be cleaned once a week using a dry cloth or tissue.

Patients should be instructed in the proper use of their inhaler (see patient information leaflet) and children should always have adult supervision when using the device. Illustrated instructions for use accompany each package.

Posology

Adults and Older people:

For the relief of acute bronchospasm and for managing intermittent episodes of asthma, one inhalation (100 micrograms) may be administered as a single starting dose; this may be increased to two inhalations (200 micrograms) if necessary.

To prevent exercise-induced bronchospasm or allergen bronchospasm two inhalations (200 micrograms) should be taken before challenge, this dose (200 micrograms) may be repeated if necessary.

Paediatric Population:

Relief of acute bronchospasm

Children aged 4 to 11 years 100 micrograms as required. The dose may be increased to two inhalations if required.

Children aged 12 years and over: Dose as per adult population.

Prevention of allergen or exercise-induced bronchospasm

Children aged 4 to 11 years 100 micrograms before challenge or exertion. The dose may be increased to two inhalations if required.

Children aged 12 years and over: Dose as per adult population.

Chronic therapy

Children aged 4 to 11 years up to 200 micrograms four times a day.

On-demand use of Easyhaler Xi Bei Ta Sulfate should not exceed four times daily. Reliance on such frequent supplementary use, or a sudden increase in dose, indicates poorly controlled or deteriorating asthma.

Children aged 12 years and over: Dose as per adult population.

On demand use of Easyhaler Xi Bei Ta Sulfate should not exceed eight inhalations (800 micrograms) in any 24 hour period.

For optimum results in most patients Easyhaler Xi Bei Ta Sulfate inhaler should be used regularly during asthmatic attacks. The bronchodilator effect of each administration of inhaled Xi Bei Ta lasts for four hours, except in patients whose asthma is becoming worse. Such patients should be warned not to increase their usage of Xi Bei Ta, but should seek medical advice in case treatment with an inhaled and/or systemic glucocorticosteroid is indicated.

Method of administration

For oral inhalation only.

This preparation is particularly useful for patients unable to use metered dose inhalers properly and for patients in whom the use of an inhalation aerosol causes irritation of airways. Inhaled Xi Bei Ta should be used only on as-needed basis at the lowest dose and frequency required.

Precautions to be taken before handling or administering the medicinal product

Instructions for use:

The protective cover of the inhaler should be opened and the dust cap removed immediately prior to use.

The inhaler should be shaken vigorously up and down 3-5 times. Whilst holding the inhaler in an upright position, between the finger and thumb, press once until a click is heard. Let inhaler click back again whilst continuing to hold in an upright position.

Inhalation should take place from either a sitting or standing position. The patient should breathe out normally and place the mouthpiece between their teeth whilst using their lips to form a seal around the mouthpiece. Patients are instructed to perform a rapid and forced inhalation through the Easyhaler device. After holding their breath for at least 5 seconds the patient can resume normal breathing. Patients should not to exhale into the device.

The mouthpiece of the inhaler should be cleaned once a week using a dry cloth or tissue.

Patients should be instructed in the proper use of their inhaler (see patient information leaflet) and children should always have adult supervision when using the device. Illustrated instructions for use accompany each package.

Xi Bei Ta are for inhalation use only, to be breathed in through the mouth, under the direction of a physician, using a suitable nebuliser.

The solution should not be injected or swallowed.

Adults (including the elderly): 2.5 mg to 5 mg salbutamol up to four times a day. Up to 40 mg per day can be given under strict medical supervision in hospital.

Paediatric Population

Children aged 12 years and over: Dose as per adult population.

Children aged 4-11 years: 2.5 mg to 5 mg up to four times a day.

Other pharmaceutical forms may be more appropriate for administration in children under 4 years old.

Infants under 18 months old: Clinical efficacy of nebulised salbutamol in infants under 18 months is uncertain. As transient hypoxia may occur supplemental oxygen therapy should be considered.

Xi Bei Ta are intended to be used undiluted. However, if prolonged delivery time (more than 10 minutes) is required, the solution may be diluted with sterile normal saline.

Intravenous or oral salbutamol is used for the management of premature labour uncomplicated by conditions such as placenta praevia, ante-partum haemorrhage or toxaemia of pregnancy, however inhaled salbutamol is not appropriate for management of premature labour. Salbutamol preparations should not be used for threatened abortion.

Intravenous or oral Xi Bei Ta is used for the management of premature labour uncomplicated by conditions such as placenta praevia, ante-partum haemorrhage or toxaemia of pregnancy, however inhaled Xi Bei Ta is not appropriate for management of premature labour. Xi Bei Ta preparations should not be used for threatened abortion.

Non-IV formulations of salbutamol must not be used to arrest uncomplicated premature labour or threatened abortion.

Bronchodilators should not be the only or main treatment in patients with severe or unstable asthma.

Severe asthma requires regular medical assessment including lung function testing as the patients are at risk of severe attacks and even death. Physicians should consider using oral corticosteroid therapy or the maximum use of inhaled corticosteroids. Increasing use of bronchodilators, particularly short-acting inhaled ß2-agonists to relieve symptoms indicates deteriorating asthma control (especially if the peak expiratory flow rate value falls and/or becomes irregular).

In the event of a previous effective dose of inhaled salbutamol failing to give relief for at least three hours or if they need more inhalations than usual, the patient should be advised to seek medical advice as soon as possible. In this situation patients should be reassessed and consideration given to an increase in their anti-inflammatory therapy, (e.g. higher doses of inhaled corticosteroids or a course of oral corticosteroids). A regular anti-inflammatory controller medication taken on a daily basis is required as soon as the patient needs inhaled ß2-agonists more than twice a week. Severe episodes of asthma must be treated in the normal way.

As there may be adverse effects associated with excessive dosing, the dosage and frequency of administration should only be increased on medical advice.

Salbutamol should be administered with caution in patients with thyrotoxicosis, cardiac insufficiency, hypokalaemia, myocardial ischaemia, tachyarrhythmia and hypertrophic obstructive cardiomyopathy.

Potentially serious hypokalaemia may result from ß2 agonist therapy, mainly from parenteral and nebulised therapy. Particular caution is advised in acute severe asthma, as this effect may be potentiated by concomitant treatment with xanthine derivatives, steroids, diuretics and by hypoxia. It is recommended that serum potassium levels are monitored in such situations.

Rarely inhalation therapy may cause bronchospasm after dosing. In this event, treatment with Salbutamol must be immediately discontinued and, if need be, replaced with another therapy.

Cardiovascular effects may be seen with sympathomimetic drugs, including salbutamol. There is some evidence from post-marketing data and published literature of rare occurrences of myocardial ischaemia associated with salbutamol. Patients with underlying severe heart disease (e.g. ischaemic heart disease, arrhythmia or severe heart failure) who are receiving salbutamol should be warned to seek medical advice if they experience chest pain or other symptoms of worsening heart disease. Attention should be paid to assessment of symptoms such as dyspnoea and chest pain, as they may be of either respiratory or cardiac origin.

One dose contains less than 10 mg lactose, which probably does not cause symptoms in lactose intolerant patients. Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine.

Bronchodilators should not be the only or main treatment in patients with severe or unstable asthma.

Severe asthma requires regular medical assessment including lung function testing as the patients are at risk of severe attacks and even death. Physicians should consider using oral corticosteroid therapy or the maximum use of inhaled corticosteroids. Increasing use of bronchodilators, particularly short-acting inhaled ß2-agonists to relieve symptoms indicates deteriorating asthma control (especially if the peak expiratory flow rate value falls and/or becomes irregular).

In the event of a previous effective dose of inhaled Xi Bei Ta failing to give relief for at least three hours or if they need more inhalations than usual, the patient should be advised to seek medical advice as soon as possible. In this situation patients should be reassessed and consideration given to an increase in their anti-inflammatory therapy, (e.g. higher doses of inhaled corticosteroids or a course of oral corticosteroids). A regular anti-inflammatory controller medication taken on a daily basis is required as soon as the patient needs inhaled ß2-agonists more than twice a week. Severe episodes of asthma must be treated in the normal way.

As there may be adverse effects associated with excessive dosing, the dosage and frequency of administration should only be increased on medical advice.

Xi Bei Ta should be administered with caution in patients with thyrotoxicosis, cardiac insufficiency, hypokalaemia, myocardial ischaemia, tachyarrhythmia and hypertrophic obstructive cardiomyopathy.

Potentially serious hypokalaemia may result from ß2 agonist therapy, mainly from parenteral and nebulised therapy. Particular caution is advised in acute severe asthma, as this effect may be potentiated by concomitant treatment with xanthine derivatives, steroids, diuretics and by hypoxia. It is recommended that serum potassium levels are monitored in such situations.

Rarely inhalation therapy may cause bronchospasm after dosing. In this event, treatment with Xi Bei Ta must be immediately discontinued and, if need be, replaced with another therapy.

Cardiovascular effects may be seen with sympathomimetic drugs, including Xi Bei Ta. There is some evidence from post-marketing data and published literature of rare occurrences of myocardial ischaemia associated with Xi Bei Ta. Patients with underlying severe heart disease (e.g. ischaemic heart disease, arrhythmia or severe heart failure) who are receiving Xi Bei Ta should be warned to seek medical advice if they experience chest pain or other symptoms of worsening heart disease. Attention should be paid to assessment of symptoms such as dyspnoea and chest pain, as they may be of either respiratory or cardiac origin.

One dose contains less than 10 mg lactose, which probably does not cause symptoms in lactose intolerant patients. Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine.

Xi Bei Ta must only be used by inhalation, to be breathed in through the mouth, and must not be injected or swallowed.

Bronchodilators should not be the only or main treatment in patients with severe or unstable asthma. Severe asthma requires regular medical assessment, including lung-function testing, as patients are at risk of severe attacks and even death. Physicians should consider using the maximum recommended dose of inhaled corticosteroid and/or oral corticosteroid therapy in these patients.

Patients receiving treatment at home should seek medical advice if treatment with Xi Bei Ta becomes less effective. The dosage or frequency of administration should only be increased on medical advice.

Patients being treated with Xi Bei Ta may also be receiving other dosage forms of short-acting inhaled bronchodilators to relieve symptoms. Increasing use of bronchodilators, in particular short-acting inhaled β2-agonists to relieve symptoms, indicates deterioration of asthma control. The patient should be instructed to seek medical advice if short-acting relief bronchodilator treatment becomes less effective or more inhalations than usual are required. In this situation patients should be assessed and consideration given to the need for increased anti-inflammatory therapy (e.g. higher doses of inhaled corticosteroid or a course of oral corticosteroid).

Severe exacerbations of asthma must be treated in the normal way.

Salbutamol should be administered cautiously to patients suffering from thyrotoxicosis.

Cardiovascular effects may be seen with sympathomimetic drugs, including salbutamol. There is some evidence from post-marketing data and published literature of rare occurrences of myocardial ischaemia associated with salbutamol. Patients with underlying severe heart disease (e.g. ischaemic heart disease, arrhythmia or severe heart failure) who are receiving salbutamol should be warned to seek medical advice if they experience chest pain or other symptoms of worsening heart disease. Attention should be paid to assessment of symptoms such as dyspnoea and chest pain, as they may be of either respiratory or cardiac origin.

Xi Bei Ta should be used with care in patients known to have received large doses of other sympathomimetic drugs.

Potentially serious hypokalaemia may result from β2-agonist therapy, mainly from parenteral and nebulised administration. Particular caution is advised in acute severe asthma as this effect may be potentiated by hypoxia and by concomitant treatment with xanthine derivatives, steroids and diuretics. Serum potassium levels should be monitored in such situations.

In common with other β-adrenoceptor agonists, salbutamol can induce reversible metabolic changes such as increased blood glucose levels. Diabetic patients may be unable to compensate for the increase in blood glucose and the development of ketoacidosis has been reported. Concurrent administration of corticosteroids can exaggerate this effect.

Lactic acidosis has been reported in association with high therapeutic doses of intravenous and nebulised short-acting beta-agonist therapy, mainly in patients being treated for an acute asthma exacerbation. Increase in lactate levels may lead to dyspnoea and compensatory hyperventilation, which could be misinterpreted as a sign of asthma treatment failure and lead to inappropriate intensification of short-acting beta-agonist treatment. It is therefore recommended that patients are monitored for the development of elevated serum lactate and consequent metabolic acidosis in this setting.

A small number of cases of acute angle-closure glaucoma have been reported in patients treated with a combination of nebulised salbutamol and ipratropium bromide. A combination of nebulised salbutamol with nebulised anticholinergics should therefore be used cautiously. Patients should receive adequate instruction in correct administration and be warned not to let the solution or mist enter the eye.

As with other inhalation therapy, paradoxical bronchospasm may occur with an immediate increase in wheezing after dosing. This should be treated immediately with an alternative presentation or a different fast-acting inhaled bronchodilator. Xi Bei Ta should be discontinued, and if necessary a different fast-acting bronchodilator instituted for on-going use.

Salbutamol Easyhaler has no or negligible influence on the ability to drive and use machines.

Xi Bei Ta Easyhaler has no or negligible influence on the ability to drive and use machines.

None reported.

The undesirable effects caused by normally used inhaled doses of salbutamol are mild, typical for sympathomimetic agents, and they usually disappear with continued treatment.

Adverse events are listed below by system organ class and frequency. Frequencies are defined as: very common (>1/10), common, (>1/100 and <1/10), uncommon (>1/1000 and <1/100), rare (>1/10,000 and <1/1000), very rare (<1/10,000) and not known (cannot be estimated from the available data).

Reporting of suspected adverse reactions

Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via Yellow Card Scheme at: www.mhra.gov.uk/yellowcard.

The undesirable effects caused by normally used inhaled doses of Xi Bei Ta are mild, typical for sympathomimetic agents, and they usually disappear with continued treatment.

Adverse events are listed below by system organ class and frequency. Frequencies are defined as: very common (>1/10), common, (>1/100 and <1/10), uncommon (>1/1000 and <1/100), rare (>1/10,000 and <1/1000), very rare (<1/10,000) and not known (cannot be estimated from the available data).

Reporting of suspected adverse reactions

Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via Yellow Card Scheme at: www.mhra.gov.uk/yellowcard.

Adverse events are listed below by system organ >

Immune system disorders

Very rare:

Hypersensitivity reactions including angioedema, urticaria, bronchospasm, hypotension and collapse

Metabolism and nutrition disorders

Rare:

Hypokalaemia.

Potentially serious hypokalaemia may result from beta₂ agonist therapy.

Unknown:

Lactic acidosis

Nervous system disorders

Common:

Tremor, headache.

Very rare:

Hyperactivity.

Cardiac disorders

Common:

Tachycardia.

Uncommon:

Palpitations

Very rare:

Cardiac arrhythmias including atrial fibrillation, supraventricular tachycardia and extrasystoles

Unknown:

Myocardial ischaemia*

Vascular disorders

Rare:

Peripheral vasodilatation.

Respiratory, thoracic and mediastinal disorders

Very rare:

Paradoxical bronchospasm.

Gastrointestinal disorders

Uncommon:

Mouth and throat irritation.

Musculoskeletal and connective tissue disorders

Uncommon:

Muscle cramps.

* reported spontaneously in post-marketing data therefore frequency regarded as unknown

Reporting of suspected adverse reactions

Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme at: www.mhra.gov.uk/yellowcard.

Excess repeat use of inhalations may produce adverse effects such as tachycardia, CNS stimulation, tremor, hypokalaemia and hyperglycaemia.

Treatment consists of discontinuation of salbutamol together with appropriate symptomatic therapy. The preferred antidote for overdosage with salbutamol is a cardioselective beta-blocking agent, but beta-blocking drugs should be used with caution in patients with a history of bronchospasm. Hypokalaemia may occur following overdose with salbutamol. Serum potassium levels should be monitored. If hypokalaemia occurs potassium replacement via the oral route should be given. In patients with severe hypokalaemia intravenous replacement may be necessary.

Excess repeat use of inhalations may produce adverse effects such as tachycardia, CNS stimulation, tremor, hypokalaemia and hyperglycaemia.

Treatment consists of discontinuation of Xi Bei Ta together with appropriate symptomatic therapy. The preferred antidote for overdosage with Xi Bei Ta is a cardioselective beta-blocking agent, but beta-blocking drugs should be used with caution in patients with a history of bronchospasm. Hypokalaemia may occur following overdose with Xi Bei Ta. Serum potassium levels should be monitored. If hypokalaemia occurs potassium replacement via the oral route should be given. In patients with severe hypokalaemia intravenous replacement may be necessary.

The most common signs and symptoms of overdose with salbutamol are transient beta agonist pharmacologically mediated events, including tachycardia, tremor, hyperactivity and metabolic effects including hypokalaemia and lactic acidosis.

Hypokalaemia may occur following overdose with salbutamol. Serum potassium levels should be monitored. Lactic acidosis has been reported in association with high therapeutic doses as well as overdoses of short-acting beta-agonist therapy, therefore monitoring for elevated serum lactate and consequent metabolic acidosis (particularly if there is persistence or worsening of tachypnea despite resolution of other signs of bronchospasm such as wheezing) may be indicated in the setting of overdose.

Pharmacotherapeutic group: Selective beta2-adrenoreceptor agonists.

ATC code: R03AC02.

Salbutamol is a selective ß2-adrenergic receptor agonist. The pharmacological effects of salbutamol are at least in part attributable to stimulation through beta-adrenergic receptors of intracellular adenyl cyclase, the enzyme that catalyses the conversion of adenosine triphosphate (ATP) to cyclic-3',5',-adenosine monophosphate (cyclic AMP). Increased cyclic AMP levels are associated with relaxation of bronchial smooth muscle and inhibition of release of mediators of immediate hypersensitivity from cells, especially from mast cells. Salbutamol also stimulates mucous secretion and mucociliary transport in the respiratory tract. Bronchial effects of inhaled salbutamol can be detected after a few minutes and duration of action is normally 4-6 hours.

Like other ß2-adrenoceptor agonists salbutamol also has cardiovascular effects in some patients as measured by changes in pulse rate, blood pressure, symptoms and ECG changes. These effects can especially be detected after oral and intravenous administration of salbutamol. Furthermore oral and intravenous salbutamol causes reduction in uterine tonicity which has been associated with pain relief in pregnancy. In addition, salbutamol has some metabolic effects. Especially intravenous and nebulised salbutamol decreases serum potassium concentrations although the effect is generally mild and transient. Salbutamol has also lipolytic effects and it has been shown to cause increases in blood glucose and insulin probably by stimulating glycogenolysis and having a stimulatory effect on ß2-receptors in pancreas cells.

Pharmacotherapeutic group: Selective beta2-adrenoreceptor agonists.

ATC code: R03AC02.

Xi Bei Ta is a selective ß2-adrenergic receptor agonist. The pharmacological effects of Xi Bei Ta are at least in part attributable to stimulation through beta-adrenergic receptors of intracellular adenyl cyclase, the enzyme that catalyses the conversion of adenosine triphosphate (ATP) to cyclic-3',5',-adenosine monophosphate (cyclic AMP). Increased cyclic AMP levels are associated with relaxation of bronchial smooth muscle and inhibition of release of mediators of immediate hypersensitivity from cells, especially from mast cells. Xi Bei Ta also stimulates mucous secretion and mucociliary transport in the respiratory tract. Bronchial effects of inhaled Xi Bei Ta can be detected after a few minutes and duration of action is normally 4-6 hours.

Like other ß2-adrenoceptor agonists Xi Bei Ta also has cardiovascular effects in some patients as measured by changes in pulse rate, blood pressure, symptoms and ECG changes. These effects can especially be detected after oral and intravenous administration of Xi Bei Ta. Furthermore oral and intravenous Xi Bei Ta causes reduction in uterine tonicity which has been associated with pain relief in pregnancy. In addition, Xi Bei Ta has some metabolic effects. Especially intravenous and nebulised Xi Bei Ta decreases serum potassium concentrations although the effect is generally mild and transient. Xi Bei Ta has also lipolytic effects and it has been shown to cause increases in blood glucose and insulin probably by stimulating glycogenolysis and having a stimulatory effect on ß2-receptors in pancreas cells.

Pharmacotherapeutic group: Andrenergics, inhalants. Selective beta-2-andrenoreceptor agonists

ATC code: R03AC02

Salbutamol is a selective β2-agonist providing short-acting (4-6 hour) bronchodilation with a fast onset (within 5 minutes) in reversible airways obstruction. At therapeutic doses it acts on the β2-adrenoceptors of bronchial muscle. With its fast onset of action, it is particularly suitable for the management and prevention of attack in asthma.

Absorption

Orally administered salbutamol is well absorbed with peak plasma concentrations occurring 1 to 4 hours after administration.

Distribution

The major proportion of inhaled Salbutamol is swallowed. The fraction that is distributed to the lung (approx. 10-25%) is rapidly seen in the circulation as free unmetabolised drug. The remainder is retained in the delivery system or is deposited in the oropharynx from where it is swallowed. The swallowed portion of an inhaled dose is absorbed from the gastrointestinal tract and undergoes considerable first-pass metabolism.

Elimination

The plasma concentrations of inhaled Salbutamol are, however, lower than those produced by usual oral doses. Salbutamol and its metabolites are rapidly excreted in the urine and faeces with about 80% of the dose being recovered in urine within 24 hours. The elimination half-life of Salbutamol is 2.7 - 5.5 hours after oral and inhaled administration.

Absorption

Orally administered Xi Bei Ta is well absorbed with peak plasma concentrations occurring 1 to 4 hours after administration.

Distribution

The major proportion of inhaled Xi Bei Ta is swallowed. The fraction that is distributed to the lung (approx. 10-25%) is rapidly seen in the circulation as free unmetabolised drug. The remainder is retained in the delivery system or is deposited in the oropharynx from where it is swallowed. The swallowed portion of an inhaled dose is absorbed from the gastrointestinal tract and undergoes considerable first-pass metabolism.

Elimination

The plasma concentrations of inhaled Xi Bei Ta are, however, lower than those produced by usual oral doses. Xi Bei Ta and its metabolites are rapidly excreted in the urine and faeces with about 80% of the dose being recovered in urine within 24 hours. The elimination half-life of Xi Bei Ta is 2.7 - 5.5 hours after oral and inhaled administration.

Salbutamol administered intravenously has a half-life of 4 to 6 hours and is cleared partly renally, and partly by metabolism to the inactive 4'-O-sulfate (phenolic sulfate) which is also excreted primarily in the urine. The faeces are a minor route of excretion. Most of a dose of salbutamol given intravenously, orally or by inhalation is excreted within 72 hours. Salbutamol is bound to plasma proteins to the extent of 10%.

After administration by the inhaled route between 10 and 20% of the dose reaches the lower airways. The remainder is retained in the delivery system or is deposited in the oropharynx from where it is swallowed. The fraction deposited in the airways is absorbed into the pulmonary tissues and circulation, but is not metabolised by the lung. On reaching the systemic circulation it becomes accessible to hepatic metabolism and is excreted, primarily in the urine, as unchanged drug and as the phenolic sulfate.

The swallowed portion of an inhaled dose is absorbed from the gastrointestinal tract and undergoes considerable first-pass metabolism to the phenolic sulfate. Both unchanged drug and conjugate are excreted primarily in the urine.

The short term toxicity has been tested in different animal species - the mouse, the rat and the dog - at doses extending to several thousand fold higher than the intended human therapeutic dose - maximally in the region of 15 µg/kg daily. The lethal doses via the intravenous route in the rodents range from 50mg/kg, via the peroral route to around 2000 mg/kg and even higher. Thus the agent exhibits low acute systemic toxicity.

Local toxicity on the airway has not been exclusively studied, but the historical evidence based on long clinical use suggests good airway tolerance.

Reported findings in repeated dose studies such as tachycardia, increases in heart weight and hypertrophy of muscle fibres are common to all potent selective beta2-agonists and are an expression of excessive beta-stimulant action. The safety margin for these effects is not known.

The subacute toxic effects on the cardiac muscle are seen at doses ranging from 0.2 to 3mg/kg. This is a manifestation of the pharmacodynamics of salbutamol at grossly elevated doses.

The doses administered in subchronic toxicity studies have been in the milligram ranges per kilogram - 0.15 to 50 - via the oral route or by inhalation. The species have been the rat (p.o. administration), and the dog (p.o. and inhalation). The toxic signs and symptoms exhibited were, as noted in the paragraph above, related to the mode of action on the adrenergic receptor.

The chronic toxicity, again, is manifested as exaggerated pharmacodynamic effects in animals.

Animal data on reproductive toxicity is quite limited. Sympathomimetics, including salbutamol, are widely used in clinical medicine in patients of fertile age. In spite of this fact, no adverse reproductive effects attributable to salbutamol are reported in the literature.

Embryotoxicity in animal studies seems to be related only to the mouse. In this species the union of the flat bones of the lower part of the skull seem to be involved. The specific mechanism of this has not been fully elucidated.

Foetal toxicity at high single or elevated chronic doses are related to energy metabolism from glycogen. Catecholamines liberate energy in the form of glucose from glycogen stored in liver and muscle. This action is mediated by glycogen synthase and phosphorylase of these tissues. Elevated foetal insulin and glucose levels suggest a higher sensitivity of the foetal pancreas to this stimulation of ß-adrenergic receptors.

The classic airways of mutagenic potential by which this agent has been tested have exhibited no increase in the incidence of mutations.

The potential of increase in the number of neoplasms shows a species and even a strain specificity, as did the effect on the delay in union flat jaw bones. Ovarian leiomyomas, benign tumours of smooth muscle, occur with a significantly higher frequency in the rat, particularly of the Spraque-Dawley strain. The other rodent species do not appear to be affected, suggesting a difference in the susceptibility of the uterine muscle of Spraque-Dawley to ß-adrenergic stimulation.

The short term toxicity has been tested in different animal species - the mouse, the rat and the dog - at doses extending to several thousand fold higher than the intended human therapeutic dose - maximally in the region of 15 µg/kg daily. The lethal doses via the intravenous route in the rodents range from 50mg/kg, via the peroral route to around 2000 mg/kg and even higher. Thus the agent exhibits low acute systemic toxicity.

Local toxicity on the airway has not been exclusively studied, but the historical evidence based on long clinical use suggests good airway tolerance.

Reported findings in repeated dose studies such as tachycardia, increases in heart weight and hypertrophy of muscle fibres are common to all potent selective beta2-agonists and are an expression of excessive beta-stimulant action. The safety margin for these effects is not known.

The subacute toxic effects on the cardiac muscle are seen at doses ranging from 0.2 to 3mg/kg. This is a manifestation of the pharmacodynamics of Xi Bei Ta at grossly elevated doses.

The doses administered in subchronic toxicity studies have been in the milligram ranges per kilogram - 0.15 to 50 - via the oral route or by inhalation. The species have been the rat (p.o. administration), and the dog (p.o. and inhalation). The toxic signs and symptoms exhibited were, as noted in the paragraph above, related to the mode of action on the adrenergic receptor.

The chronic toxicity, again, is manifested as exaggerated pharmacodynamic effects in animals.

Animal data on reproductive toxicity is quite limited. Sympathomimetics, including Xi Bei Ta, are widely used in clinical medicine in patients of fertile age. In spite of this fact, no adverse reproductive effects attributable to Xi Bei Ta are reported in the literature.

Embryotoxicity in animal studies seems to be related only to the mouse. In this species the union of the flat bones of the lower part of the skull seem to be involved. The specific mechanism of this has not been fully elucidated.

Foetal toxicity at high single or elevated chronic doses are related to energy metabolism from glycogen. Catecholamines liberate energy in the form of glucose from glycogen stored in liver and muscle. This action is mediated by glycogen synthase and phosphorylase of these tissues. Elevated foetal insulin and glucose levels suggest a higher sensitivity of the foetal pancreas to this stimulation of ß-adrenergic receptors.

The classic airways of mutagenic potential by which this agent has been tested have exhibited no increase in the incidence of mutations.

The potential of increase in the number of neoplasms shows a species and even a strain specificity, as did the effect on the delay in union flat jaw bones. Ovarian leiomyomas, benign tumours of smooth muscle, occur with a significantly higher frequency in the rat, particularly of the Spraque-Dawley strain. The other rodent species do not appear to be affected, suggesting a difference in the susceptibility of the uterine muscle of Spraque-Dawley to ß-adrenergic stimulation.

In an oral fertility and general reproductive performance study in rats at doses of 2 and 50 mg/kg/day, with the exception of a reduction in number of weanlings surviving to day 21 post partum at 50 mg/kg/day, there were no adverse effects on fertility, embryofetal development, litter size, birth weight or growth rate.