by Dr. Manura Nanayakkara

Created on: May 29, 2010

Gentamicin is an antibiotic in aminoglycoside family. Popular brands are Cidomycin, and Genticin. It is available in intravenous and topical preparations. Intravenous form is used in serious bacterial infections and topical form used in eye, ear and skin infections. Oral form is not available.

Topical preparations

The use of gentamicin topical preparations may result in alteration of normal microbial flora of applied areas. This can result in overgrowth of non-susceptible microorganisms such as fungi.

Skin

Gentamicin for skin is available as creams and gels. Some preparations are available with a mixture of steroids, antifungals, paraben and antipruritics. Side effects are low with gentamicin skin applications. But other ingredients have side effects of their own (Parabens can commonly cause allergic contact dermatitis). Local irritation including erythema and pruritus occur rarely following topical application. Very rarely photosensitization has been reported with gentamicin. Side effects and toxic effects of intravenous form can occur, if applied to large skin lesions.

Eye and ear

Side effects are also low with eye preparations. However, sensitization to the drug may occur. If irritation and sensitization occurs during therapy, the medication should be discontinued. Transient irritation, burning, or stinging sensation can occasionally occur with gentamicin eye preparations. Gentamicin eye preparations should not be taken by the patients who are allergic to aminoglycoside antibiotics.

Intravenous form

Intravenous form is used mainly in infective endocarditis, severe urinary tract infections, meningitis, and pelvic inflammatory disease.

Serious allergic reactions can occur with patients who are allergic to aminoglycoside antibiotics. Before starting the drug doctor will ask patients allergic history (to drugs, food and etcetera).

Before starting gentamicin doctors will check, whether patient has existing kidney diseases, because gentamicin is known to cause serious kidney damage. Kidneys are assessed during the therapy as well.

Nausea and vomiting can occur with certain patients receiving intravenous gentamicin.

Gentamicin should not be used in patients with myasthenia gravis.

Another serious side effect is complete or partial deafness, which is rare. Reduced magnesium levels in blood have been detected in a small number of patients as well.

Pregnancy

Doctors will avoid using this drug in pregnancy unless it is essential. Gentamicin can cause complete or partial deafness in newborn, if used in second and last three months.

Drug interactions

Gentamicin increases blood concentration of digoxin.

Blood concentration of gentamicin is increased by indomethacin, especially in newborns.

Co administration with amphotericin, cephalosporins, cyclosporine colistin, and vancomycin may results in increased risk of kidney damage.

Drugs like Lasix can increase the risk of complete or partial deafness.

Blood calcium levels will decrease if given with bisphosphonates (e.g. Alendronate, risendronate and sodium etidronate)

Sources

British National Formulary 58th edition

AHFS Drug Information

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