Components:
Method of action:
Treatment option:
Medically reviewed by Militian Inessa Mesropovna, PharmD. Last updated on 18.03.2022
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Benzylpenicillin is indicated for most wound infections, pyogenic infections of the skin, soft tissue infections and infections of the nose, throat, nasal sinuses, respiratory tract and middle ear, etc.
It is also indicated for the following infections caused by penicillin-sensitive microorganisms: Generalised infections, septicaemia and pyaemia from susceptible bacteria. Acute and chronic osteomyelitis, sub-acute bacterial endocarditis and meningitis caused by susceptible organisms. Suspected meningococcal disease. Gas gangrene, tetanus, actinomycosis, anthrax, leptospirosis, rat-bite fever, listeriosis, severe Lyme disease, and prevention of neonatal group B streptococcal infections. Complications secondary to gonorrhoea and syphilis (e.g. gonococcal arthritis or endocarditis, congenital syphilis and neurosyphilis). Diphtheria, brain abscesses and pasteurellosis.
Consideration should be given to official local guidance (e.g. national recommendations) on the appropriate use of antibacterial agents.
Susceptibility of the causative organism to the treatment should be tested (if possible), although therapy may be initiated before the results are available
Retardillin is indicated for most wound infections, pyogenic infections of the skin, soft tissue infections and infections of the nose, throat, nasal sinuses, respiratory tract and middle ear, etc.
It is also indicated for the following infections caused by penicillin-sensitive microorganisms: Generalised infections, septicaemia and pyaemia from susceptible bacteria. Acute and chronic osteomyelitis, sub-acute bacterial endocarditis and meningitis caused by susceptible organisms. Suspected meningococcal disease. Gas gangrene, tetanus, actinomycosis, anthrax, leptospirosis, rat-bite fever, listeriosis, severe Lyme disease, and prevention of neonatal group B streptococcal infections. Complications secondary to gonorrhoea and syphilis (e.g. gonococcal arthritis or endocarditis, congenital syphilis and neurosyphilis). Diphtheria, brain abscesses and pasteurellosis.
Consideration should be given to official local guidance (e.g. national recommendations) on the appropriate use of antibacterial agents.
Susceptibility of the causative organism to the treatment should be tested (if possible), although therapy may be initiated before the results are available
Route of administration:
Intramuscular, intravenous.
Preparation of solutions:
Pharmaceutical preparation
Only freshly prepared solutions should be used. Reconstituted solutions of Retardillin are intended for immediate administration.
1200 mg vials
Intravenous Injection: 1200 mg (2 mega units) dissolved in at least 8 ml of Sodium Chloride Injection BP or Water for Injections BP.
Intravenous Infusion: It is recommended that 1200 mg (2 mega units) should be dissolved in at least 20 ml of Sodium Chloride Injection BP or Water for Injections BP.
Sodium overload and/or heart failure may occur if Retardillin is administered in sodium-containing solvents to patients who suffer from renal failure and/or heart failure. Therefore, for such patients, Retardillin should not be reconstituted in sodium-containing liquids such as Sodium Chloride Injection BP or Ringer's solution.
Dosage and administration:
The following dosages apply to both intramuscular and intravenous injection.
Alternate sites should be used for repeated injections.
Adults
600 to 3,600 mg (1 to 6 mega units) daily, divided into 4 to 6 doses, depending on the indication. Higher doses (up to 14.4 g/day (24 mega units) in divided doses) may be given in serious infections such as adult meningitis by the intravenous route.
In bacterial endocarditis, 7.2 to 12 g (12 to 20 mega units) or more may be given daily in divided doses by the intravenous route, often by infusion.
Doses up to 43.2 g (72 mega units) per day may be necessary for patients with rapidly spreading gas gangrene.
High doses should be administered by intravenous injection or infusion, with intravenous doses in excess of 1.2g (2 mega units) being given slowly, taking at least one minute for each 300 mg (0.5 mega unit) to avoid high levels causing irritation of the central nervous system and/or electrolyte imbalance.
High dosage of Retardillin may result in hypernatraemia and hypokalaemia unless the sodium content is taken into account.
For the prevention of Group B Streptococcal disease of the newborn, a 3 g (5 mega units) loading dose should be given to the mother initially, followed by 1.5 g (2.5 mega units) every 4 hours until delivery.
Children aged 1 month to 12 years
100 mg/kg/day in 4 divided doses; not exceeding 4 g/day.
Infants 1-4 weeks
75 mg/kg/day in 3 divided doses.
Newborn Infants
50 mg/kg/day in 2 divided doses.
Meningococcal disease
| Children 1 month to 12 years: | 180-300 mg/kg/day in 4-6 divided doses, not exceeding 12 g/day. |
| Infants 1-4 weeks: | 150 mg/kg/day in 3 divided doses. |
| Newborn infants: | 100 mg/kg/day in 2 divided doses. |
| Adults and children over 12 years: | 2.4 g every 4 hours |
Suspected meningococcal disease
If meningococcal disease is suspected general practitioners should give a single dose of Retardillin, before transferring the patient to hospital, as follows:
| Adults and children over 10 years: | 1,200 mg IV (or IM) |
| Children 1-9 years: | 600 mg IV (or IM) |
| Children under 1 year: | 300 mg IV (or IM) |
Premature babies and neonates
Dosing should not be more frequent than every 8 or 12 hours in this age group, since renal clearance is reduced at this age and the mean half-life of benzylpenicillin may be as long as 3 hours.
Since infants have been found to develop severe local reactions to intramuscular injections, intravenous treatment should preferably be used.
Patients with renal insufficiency
For doses of 0.6-1.2 g (1-2 mega units) the dosing interval should be no more frequent than every 8-10 hours.
For high doses e.g. 14.4 g (24 mega units) required for the treatment of serious infections such as meningitis, the dosage and dose interval of Retardillin should be adjusted in accordance with the following schedule:
| Creatinine clearance (ml per minute) | Dose (g) | Dose (mega units) | Dosing interval (hours) |
| 125 | 1.2 or 1.8 | 2 or 3 | 2 3 |
| 60 | 1.2 | 2 | 4 |
| 40 | 0.9 | 1.5 | 4 |
| 20 | 0.6 | 1.0 | 4 |
| 10 | 0.6 | 1.0 | 6 |
| Nil | 0.3 or 0.6 | 0.5 or 1.0 | 6 8 |
The dose in the above table should be further reduced to 300 mg (0.5 mega units) 8 hourly if advanced liver disease is associated with severe renal failure.
If haemodialysis is required, an additional dose of 300 mg (0.5 mega units) should be given 6 hourly during the procedure.
Elderly Patients
Elimination may be delayed in elderly patients and dose reduction may be necessary.
Route of administration:
Intramuscular, intravenous.
Preparation of solutions:
Pharmaceutical preparation
Only freshly prepared solutions should be used. Reconstituted solutions of Retardillin sodium are intended for immediate administration.
1200 mg vials
Intravenous Injection: 1200 mg (2 mega units) dissolved in at least 8 ml of Sodium Chloride Injection BP or Water for Injections BP.
Intravenous Infusion: It is recommended that 1200 mg (2 mega units) should be dissolved in at least 20 ml of Sodium Chloride Injection BP or Water for Injections BP.
Sodium overload and/or heart failure may occur if Retardillin sodium is administered in sodium-containing solvents to patients who suffer from renal failure and/or heart failure. Therefore, for such patients, Retardillin sodium should not be reconstituted in sodium-containing liquids such as Sodium Chloride Injection BP or Ringer's solution.
Dosage and administration:
The following dosages apply to both intramuscular and intravenous injection.
Alternate sites should be used for repeated injections.
Adults
600 to 3,600 mg (1 to 6 mega units) daily, divided into 4 to 6 doses, depending on the indication. Higher doses (up to 14.4 g/day (24 mega units) in divided doses) may be given in serious infections such as adult meningitis by the intravenous route.
In bacterial endocarditis, 7.2 to 12 g (12 to 20 mega units) or more may be given daily in divided doses by the intravenous route, often by infusion.
Doses up to 43.2 g (72 mega units) per day may be necessary for patients with rapidly spreading gas gangrene.
High doses should be administered by intravenous injection or infusion, with intravenous doses in excess of 1.2g (2 mega units) being given slowly, taking at least one minute for each 300 mg (0.5 mega unit) to avoid high levels causing irritation of the central nervous system and/or electrolyte imbalance.
High dosage of Retardillin sodium may result in hypernatraemia and hypokalaemia unless the sodium content is taken into account.
For the prevention of Group B Streptococcal disease of the newborn, a 3 g (5 mega units) loading dose should be given to the mother initially, followed by 1.5 g (2.5 mega units) every 4 hours until delivery.
Children aged 1 month to 12 years
100 mg/kg/day in 4 divided doses; not exceeding 4 g/day.
Infants 1-4 weeks
75 mg/kg/day in 3 divided doses.
Newborn Infants
50 mg/kg/day in 2 divided doses.
Meningococcal disease
| Children 1 month to 12 years: | 180-300 mg/kg/day in 4-6 divided doses, not exceeding 12 g/day. |
| Infants 1-4 weeks: | 150 mg/kg/day in 3 divided doses. |
| Newborn infants: | 100 mg/kg/day in 2 divided doses. |
| Adults and children over 12 years: | 2.4 g every 4 hours |
Suspected meningococcal disease
If meningococcal disease is suspected general practitioners should give a single dose of Retardillin sodium, before transferring the patient to hospital, as follows:
| Adults and children over 10 years: | 1,200 mg IV (or IM) |
| Children 1-9 years: | 600 mg IV (or IM) |
| Children under 1 year: | 300 mg IV (or IM) |
Premature babies and neonates
Dosing should not be more frequent than every 8 or 12 hours in this age group, since renal clearance is reduced at this age and the mean half-life of Retardillin may be as long as 3 hours.
Since infants have been found to develop severe local reactions to intramuscular injections, intravenous treatment should preferably be used.
Patients with renal insufficiency
For doses of 0.6-1.2 g (1-2 mega units) the dosing interval should be no more frequent than every 8-10 hours.
For high doses e.g. 14.4 g (24 mega units) required for the treatment of serious infections such as meningitis, the dosage and dose interval of Retardillin sodium should be adjusted in accordance with the following schedule:
| Creatinine clearance (ml per minute) | Dose (g) | Dose (mega units) | Dosing interval (hours) |
| 125 | 1.2 or 1.8 | 2 or 3 | 2 3 |
| 60 | 1.2 | 2 | 4 |
| 40 | 0.9 | 1.5 | 4 |
| 20 | 0.6 | 1.0 | 4 |
| 10 | 0.6 | 1.0 | 6 |
| Nil | 0.3 or 0.6 | 0.5 or 1.0 | 6 8 |
The dose in the above table should be further reduced to 300 mg (0.5 mega units) 8 hourly if advanced liver disease is associated with severe renal failure.
If haemodialysis is required, an additional dose of 300 mg (0.5 mega units) should be given 6 hourly during the procedure.
Elderly Patients
Elimination may be delayed in elderly patients and dose reduction may be necessary.
Allergy to penicillins. Hypersensitivity to any ingredient of the preparation.
Cross allergy to other beta-lactams such as cephalosporins should be taken into account.
600 mg benzylpenicillin contains 1.68 mmol of sodium. Massive doses of Retardillin can cause hypokalaemia and sometimes hypernatraemia. Use of a potassium-sparing diuretic may be helpful. In patients undergoing high-dose treatment for more than 5 days, electrolyte balance, blood counts and renal functions should be monitored.
In the presence of impaired renal function, large doses of penicillin can cause cerebral irritation, convulsions and coma.
Skin sensitisation may occur in persons handling the antibiotic and care should be taken to avoid contact with the substance.
It should be recognised that any patient with a history of allergy, especially to drugs, is more likely to develop a hypersensitivity reaction to penicillin. Patients should be observed for 30 minutes after administration and if an allergic reaction occurs the drug should be withdrawn and appropriate treatment given.
Delayed absorption from the intramuscular depot may occur in diabetics.
Prolonged use of benzylpenicillin may occasionally result in an overgrowth of non-susceptible organisms or yeast and patients should be observed carefully for superinfections.
Pseudomembranous colitis should be considered in patients who develop severe and persistent diarrhoea during or after receiving benzylpenicillin. In this situation, even if Clostridium difficile is only suspected, administration of benzylpenicillin should be discontinued and appropriate treatment given.
600 mg Retardillin contains 1.68 mmol of sodium. Massive doses of Retardillin Sodium can cause hypokalaemia and sometimes hypernatraemia. Use of a potassium-sparing diuretic may be helpful. In patients undergoing high-dose treatment for more than 5 days, electrolyte balance, blood counts and renal functions should be monitored.
In the presence of impaired renal function, large doses of penicillin can cause cerebral irritation, convulsions and coma.
Skin sensitisation may occur in persons handling the antibiotic and care should be taken to avoid contact with the substance.
It should be recognised that any patient with a history of allergy, especially to drugs, is more likely to develop a hypersensitivity reaction to penicillin. Patients should be observed for 30 minutes after administration and if an allergic reaction occurs the drug should be withdrawn and appropriate treatment given.
Delayed absorption from the intramuscular depot may occur in diabetics.
Prolonged use of Retardillin may occasionally result in an overgrowth of non-susceptible organisms or yeast and patients should be observed carefully for superinfections.
Pseudomembranous colitis should be considered in patients who develop severe and persistent diarrhoea during or after receiving Retardillin. In this situation, even if Clostridium difficile is only suspected, administration of Retardillin should be discontinued and appropriate treatment given.
None
Blood and Lymphatic System Disorders
Rare (0.01% - 0.1%)
Haemolytic anaemia and granulocytopenia (neutropenia), agranulocytosis, leucopenia and thrombocytopenia, have been reported in patients receiving prolonged high doses of Retardillin (eg. Subacute bacterial endocarditis).
Immune System Disorders
Very Common (>10%)
Patients undergoing treatment for syphilis or neurosyphilis with benzylpenicillin may develop a Jarisch-Herxheimer reaction.
Common (1-10%)
Hypersensitivity to penicillin in the form of rashes (all types), fever, and serum sickness may occur (1-10% treated patients). These may be treated with antihistamine drugs.
Rare (0.01%-0.1%)
More rarely, anaphylactic reactions have been reported (<0.05% treated patients).
Nervous System Disorders
Rare (0.01%-.01%)
Central nervous system toxicity, including convulsions, has been reported with massive doses over 60 g per day and in patients with severe renal impairment.
Renal and Urinary Disorders
Rare (0.01%-0.1%)
Interstitial nephritis has been reported after intravenous Retardillin at doses of more than 12 g per day.
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.
Blood and Lymphatic System Disorders
Rare (0.01% - 0.1%)
Haemolytic anaemia and granulocytopenia (neutropenia), agranulocytosis, leucopenia and thrombocytopenia, have been reported in patients receiving prolonged high doses of Retardillin sodium (eg. Subacute bacterial endocarditis).
Immune System Disorders
Very Common (>10%)
Patients undergoing treatment for syphilis or neurosyphilis with Retardillin may develop a Jarisch-Herxheimer reaction.
Common (1-10%)
Hypersensitivity to penicillin in the form of rashes (all types), fever, and serum sickness may occur (1-10% treated patients). These may be treated with antihistamine drugs.
Rare (0.01%-0.1%)
More rarely, anaphylactic reactions have been reported (<0.05% treated patients).
Nervous System Disorders
Rare (0.01%-.01%)
Central nervous system toxicity, including convulsions, has been reported with massive doses over 60 g per day and in patients with severe renal impairment.
Renal and Urinary Disorders
Rare (0.01%-0.1%)
Interstitial nephritis has been reported after intravenous Retardillin sodium at doses of more than 12 g per day.
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.
Excessive blood levels of Retardillin can be corrected by haemodialysis.
Excessive blood levels of Retardillin sodium can be corrected by haemodialysis.
Pharmacotherapeutic group: Beta-lactamase sensitive penicillins.
ATC code: J01 CE01.
General Properties:
Retardillin is a beta-lactam antibiotic. It is bacteriocidal by inhibiting bacterial cell wall biosynthesis.
Breakpoints:
The tentative breakpoints (British Society for Antimicrobial Chemotherapy, BSAC) for Retardillin are as follows:
| Organism | S ≤ (mg/L) | I (mg/L) | R > (mg/L) |
| Streptococcus pneumoniae Neisseria gonorrhoeae | 0.06 | 0.12-1.0 | 2.0 |
| Neisseria meningitides | 0.06 | 0.12 | |
| Haemolytic streptococci Staphylococci Moraxella catarrhalis Haemophilus influenzae | 0.12 | 0.25 | |
| Rapidly growing anaerobes | 1.0 | 2.0 |
S = Susceptible, I = Intermediate susceptibility, R = Resistant
Susceptibility:
The prevalence of resistance may vary geographically and with time for selected species and local information on resistance is desirable, particularly when treating severe infections. The following table gives only approximate guidance on probabilities whether microorganisms will be susceptible to Retardillin or not.
| Susceptible and intermediately susceptible microorganisms | ||
| Type of Microorganism | Microorganism | Range of acquired resistance |
| Aerobic Gram-positive microorganisms | - Bacillus anthracis | 0%** |
| - Corynebacterium diphtheriae | 0%* | |
| - Haemolytic streptococci (including Streptococcus pyogenes) | 0%*-3%** | |
| - Listeria monocytogenes | 0%** | |
| - Streptococcus pneumoniae | 4%*-40%** | |
| - Streptococcus viridans | 3-32%* | |
| Aerobic Gram-negative microorganisms | - Neisseria gonorrhoeae | 9-10%* |
| - Neisseria meningitidis | 18%* | |
| - Pasteurella multocida | 0%*** | |
| Anaerobic microorganisms | - Actinomyces israelii | 8%** |
| - Fusobacterium nucleatum and Fusobacterium necrophorum | Usually sensitive | |
| - Gram-positive sporing bacilli (including Clostridium tetani and Clostridium perfringens (welchii)) | 14%** | |
| - Gram-positive cocci (including peptostreptococcus) | 7%* | |
| Other microorganisms | - Borrelia bugdorferi | Usually sensitive |
| - Capnocytophaga canimorosus | Usually sensitive | |
| - Leptospirae | Usually sensitive | |
| - Streptobacillus moniliformis and spirrillum minus | Usually sensitive | |
| - Treponema pallidum | 0%*** | |
* UK data; ** European data, ***Global data
| Insusceptible microorganisms | ||
| Type of Microorganism | Microorganism | Range of acquired resistance |
| Aerobic Gram-positive microorganisms | - Coagulase negative Staphylococcus | 71-81%* |
| - Enterococcus Spp | Resistant | |
| - Staphylococcus aureus | 79-87%* | |
| Aerobic Gram-negative microorganisms | - Acinetobacter | Resistant |
| - Bordetella pertussis | Generally resistant | |
| - Brucella spp. | Resistant | |
| - Enterobacteriaceae (including Escherichia coli, Salmonella, Shigella, Enterobacter, Klebsiella, Proteus, Citrobacter). | Generally resistant | |
| - Haemophilus influenzae | Resistant | |
| - Pseudomonas | Resistant | |
| Anaerobic microorganisms | - Bacteroides fragilis | 100%*** |
* UK data; ** European data, *** Global data
Other Information:
Known Resistance Mechanisms and Cross-resistance
Penicillin resistance can be mediated by alteration of penicillin binding proteins or development of beta-lactamases.
Resistance to penicillin may be associated with cross-resistance to a variety of other beta lactam antibiotics either due to a shared target site that is altered, or due to a beta-lactamase with a broad range of substrate molecules. In addition to this, cross resistance to unrelated antibiotics can develop due to more than one resistance gene being present on a mobile section of DNA (e.g. plasmid, transposon etc) resulting in two or more resistance mechanisms being transferred to a new organism at the same time.
Pharmacotherapeutic group: Beta-lactamase sensitive penicillins.
ATC code: J01 CE01.
General Properties:
Retardillin sodium is a beta-lactam antibiotic. It is bacteriocidal by inhibiting bacterial cell wall biosynthesis.
Breakpoints:
The tentative breakpoints (British Society for Antimicrobial Chemotherapy, BSAC) for Retardillin sodium are as follows:
| Organism | S ≤ (mg/L) | I (mg/L) | R > (mg/L) |
| Streptococcus pneumoniae Neisseria gonorrhoeae | 0.06 | 0.12-1.0 | 2.0 |
| Neisseria meningitides | 0.06 | 0.12 | |
| Haemolytic streptococci Staphylococci Moraxella catarrhalis Haemophilus influenzae | 0.12 | 0.25 | |
| Rapidly growing anaerobes | 1.0 | 2.0 |
S = Susceptible, I = Intermediate susceptibility, R = Resistant
Susceptibility:
The prevalence of resistance may vary geographically and with time for selected species and local information on resistance is desirable, particularly when treating severe infections. The following table gives only approximate guidance on probabilities whether microorganisms will be susceptible to Retardillin sodium or not.
| Susceptible and intermediately susceptible microorganisms | ||
| Type of Microorganism | Microorganism | Range of acquired resistance |
| Aerobic Gram-positive microorganisms | - Bacillus anthracis | 0%** |
| - Corynebacterium diphtheriae | 0%* | |
| - Haemolytic streptococci (including Streptococcus pyogenes) | 0%*-3%** | |
| - Listeria monocytogenes | 0%** | |
| - Streptococcus pneumoniae | 4%*-40%** | |
| - Streptococcus viridans | 3-32%* | |
| Aerobic Gram-negative microorganisms | - Neisseria gonorrhoeae | 9-10%* |
| - Neisseria meningitidis | 18%* | |
| - Pasteurella multocida | 0%*** | |
| Anaerobic microorganisms | - Actinomyces israelii | 8%** |
| - Fusobacterium nucleatum and Fusobacterium necrophorum | Usually sensitive | |
| - Gram-positive sporing bacilli (including Clostridium tetani and Clostridium perfringens (welchii)) | 14%** | |
| - Gram-positive cocci (including peptostreptococcus) | 7%* | |
| Other microorganisms | - Borrelia bugdorferi | Usually sensitive |
| - Capnocytophaga canimorosus | Usually sensitive | |
| - Leptospirae | Usually sensitive | |
| - Streptobacillus moniliformis and spirrillum minus | Usually sensitive | |
| - Treponema pallidum | 0%*** | |
* UK data; ** European data, ***Global data
| Insusceptible microorganisms | ||
| Type of Microorganism | Microorganism | Range of acquired resistance |
| Aerobic Gram-positive microorganisms | - Coagulase negative Staphylococcus | 71-81%* |
| - Enterococcus Spp | Resistant | |
| - Staphylococcus aureus | 79-87%* | |
| Aerobic Gram-negative microorganisms | - Acinetobacter | Resistant |
| - Bordetella pertussis | Generally resistant | |
| - Brucella spp. | Resistant | |
| - Enterobacteriaceae (including Escherichia coli, Salmonella, Shigella, Enterobacter, Klebsiella, Proteus, Citrobacter). | Generally resistant | |
| - Haemophilus influenzae | Resistant | |
| - Pseudomonas | Resistant | |
| Anaerobic microorganisms | - Bacteroides fragilis | 100%*** |
* UK data; ** European data, *** Global data
Other Information:
Known Resistance Mechanisms and Cross-resistance
Penicillin resistance can be mediated by alteration of penicillin binding proteins or development of beta-lactamases.
Resistance to penicillin may be associated with cross-resistance to a variety of other beta lactam antibiotics either due to a shared target site that is altered, or due to a beta-lactamase with a broad range of substrate molecules. In addition to this, cross resistance to unrelated antibiotics can develop due to more than one resistance gene being present on a mobile section of DNA (e.g. plasmid, transposon etc) resulting in two or more resistance mechanisms being transferred to a new organism at the same time.
Retardillin rapidly appears in the blood following intramuscular injection of water-soluble salts and maximum concentrations are usually reached in 15-30 minutes. Peak plasma concentrations of about 12 mcg/ml have been reported after doses of 600 mg with therapeutic plasma concentrations for most susceptible organisms detectable for about 5 hours. Approximately 60% of the dose injected is reversibly bound to plasma protein.
In adults with normal renal function the plasma half-life is about 30 minutes. Most of the dose (60-90%) undergoes renal elimination, 10% by glomerular filtration and 90% by tubular secretion. Tubular secretion is inhibited by probenecid, which is sometimes given to increase plasma penicillin concentrations. Biliary elimination of Retardillin accounts for only a minor fraction of the dose.
Retardillin sodium rapidly appears in the blood following intramuscular injection of water-soluble salts and maximum concentrations are usually reached in 15-30 minutes. Peak plasma concentrations of about 12 mcg/ml have been reported after doses of 600 mg with therapeutic plasma concentrations for most susceptible organisms detectable for about 5 hours. Approximately 60% of the dose injected is reversibly bound to plasma protein.
In adults with normal renal function the plasma half-life is about 30 minutes. Most of the dose (60-90%) undergoes renal elimination, 10% by glomerular filtration and 90% by tubular secretion. Tubular secretion is inhibited by probenecid, which is sometimes given to increase plasma penicillin concentrations. Biliary elimination of Retardillin sodium accounts for only a minor fraction of the dose.
There are no pre-clinical data of relevance to the prescriber which are additional to that already included in other sections of the SmPC.
Retardillin and solutions that contain metal ions should be administered separately.
Retardillin should not be administered in the same syringe / giving set as amphotericin B, cimetidine, cytarabine, flucloxacillin, hydroxyzine, methylprednisolone, or promethazine since it is incompatible with these drugs.
In the absence of compatibility studies, this medicinal product must not be mixed with other medicinal products
Retardillin sodium and solutions that contain metal ions should be administered separately.
Retardillin sodium should not be administered in the same syringe / giving set as amphotericin B, cimetidine, cytarabine, flucloxacillin, hydroxyzine, methylprednisolone, or promethazine since it is incompatible with these drugs.
In the absence of compatibility studies, this medicinal product must not be mixed with other medicinal products
After contact with skin, wash immediately with water. In case of contact with eyes, rinse immediately with plenty of water and seek medical advice if discomfort persists.
Any unused medicinal product or waste material should be disposed of in accordance with local requirements.
