Gentin

This medicine is indicated in adults and children:

1. For the treatment of eczema and infection of the outer ear (otitis externa).

2. For prophylaxis against otitis externa following trauma.

3. For post-operative local use in surgery to infected mastoid cavities.

Posology

Adults, the elderly and the paediatric population

The area should be cleaned and 2 - 4 drops instilled in the affected ear three to four times a day and at night. Alternatively, wicks medicated with this medicine may be placed in the external ear or mastoid cavity.

Method of administration

Auricular use only.

Myasthenia gravis.

Known or suspected perforation of the ear drum.

Long-term continuous topical therapy should be avoided. Prolonged use may lead to skin sensitisation and the emergence of resistant organisms. Cross sensitivity with other aminoglycoside antibiotics may occur.

In severe infections, topical use of this medicine should be supplemented with appropriate systemic antibiotic treatment.

The condition of the ear drum must always be checked before this medicinal product is prescribed. The medicinal product must not be used if the integrity of the ear drum cannot be guaranteed.

Gentamicin may cause irreversible partial or total deafness when given systemically or when applied topically to open wounds or damaged skin. This effect is dose-related and is enhanced by renal and/or hepatic impairment and is more likely in the elderly.

Irreversible toxic effects may result from direct contact of gentamicin with the middle and inner ear. The benefits of gentamicin therapy should be considered against the risk of infection itself causing hearing loss.

In infants there is a theoretical risk that sufficient steroid may be absorbed to cause adrenal suppression.

Serious adverse reactions including neurotoxicity, ototoxicity and nephrotoxicity have occurred in patients receiving systemic gentamicin therapy. Although these effects have not been reported following topical otic use of gentamicin, caution is advised when used concomitantly with systemic aminoglycosides.

This medicine contains benzalkonium chloride

Irritant, may cause skin reactions.

Co-treatment with CYP3A inhibitors, including cobicistat-containing products, is expected to increase the risk of systemic side-effects. The combination should be avoided unless the benefit outweighs the increased risk of systemic corticosteroid side-effects, in which case patients should be monitored for systemic corticosteroid side-effects.

Visual disturbance

Visual disturbance may be reported with systemic and topical corticosteroid use. If a patient presents with symptoms such as blurred vision or other visual disturbances, the patient should be considered for referral to an ophthalmologist for evaluation of possible causes which may include cataract, glaucoma or rare diseases such as central serous chorioretinopathy (CSCR) which have been reported after use of systemic and topical corticosteroids.

Not relevant.

In the event of irritation, sensitisation or super-infection, treatment with Gentin HC Ear drops should be discontinued and appropriate therapy instituted. The undesirable effects listed below have been reported at the following frequency:

Not known (cannot be estimated from 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 the Yellow Card Scheme, www.mhra.gov.uk/yellowcard.

Not applicable.

Pharmacotherapeutic group: Antibiotic

ATC code: S03AA

Mechanism of action:

Gentamicin is mixture of antibiotic substances produced by the growth of micromonospora purpurea. It is a bactericidal antibiotic which acts by inhibiting protein synthesis. It has greater antibacterial activity than streptomycin, neomycin or kanamycin.

Gentamicin exerts a number of effects on cells of susceptible bacteria. It affects the integrity of the plasma membrane and the metabolism of RNA, but it's most important effect is inhibition of protein synthesis at the level of the 30s ribosomal subunit.

Corticosteroids, such as hydrocortisone acetate, are used in pharmacological doses for their anti-inflammatory and immuno-suppressant glucocorticoid properties which suppress the clinical manifestation of disease in a wide range of disorders.

Absorption:

Topical application of gentamicin can result in some systemic absorption. Treatment of large areas can result in plasma concentrations of up to 1μg/ml.

Gentamicin is 70-85% bound to plasma albumin following administration.

Effective plasma concentration is 4 - 8ug/ml

The volume of distribution (^V_D) is 0.3 1/kg

Hydrocortisone acetate is not absorbed through the skin as rapidly as hydrocortisone and therefore has a prolonged action. Some is absorbed systemically, where greater than 90% is protein bound.

Elimination:

> 90% Gentamicin is excreted unchanged in the urine by glomerular filtration.

T_½ = 2 - 3 hours in individuals with normal kidney function, but can be increased in cases of renal insufficiency.

The elimination rate constant is;

0.02 Hr^-1 for anuric patients*

0.30 Hr^-1 normal

*Therefore in those with anuria care must be exercised.

> 70% hydrocortisone acetate is metabolised by the liver. The metabolites are excreted in the urine.

Plasma T_½ = 1½ hours.

Not applicable.

Any unused medicinal product or waste material should be disposed of in accordance with local requirements.