Gentamicin sulphate is a chemical compound, a mixture of gentamicin C1, C1a, C2 and C2a sulphate salts, consisting of aminocyclitol 2-deoxystreptamine and two amino sugars, that belongs to the aminoglycoside class of antibiotic substances.

It appears as a white or coloured powder that is hygroscopic and odourless, highly polar and highly soluble in water.

What it is used for and where

Medical

Take only under medical supervision

Gentamicin is an antibiotic discovered and produced by the pharmaceutical company Schering-Plough Corporation, isolated from a genus of actinomycetes (Gram-positive bacteria) Micromonospora purpurea. which has demonstrated broad-spectrum activity against organisms such as Proteus, Pseudomonas (1) and Gram-positive and Gram-negative bacteria. It can therefore be defined as a natural aminoglycoside bactericidal, antimicrobial fermentation antibiotic. Aminoglycoside antibiotics, the progenitors of which were first penicillin and then streptomycin, are used to treat serious infections, although their efficacy is now hampered by bacterial strains that have developed defences and resistance. As an active pharmaceutical ingredient it consists of gentamicin C1, gentamicin C1a, gentamicin C2, gentamicin C2a and, to a lesser extent, gentamicin C2b (2).

Gentamicin sulphate is used in ophthalmic eye drops especially against infections caused by Gram-negative bacteria, in the treatment of pyoderma, skin infections, Meniere's disease, bladder irrigation, respiratory infections, osteomyelitis, osteitis.

Safety

Low-dose Gentamicin is used to reduce the risk of macular infarction in the treatment and prophylaxis of endophthalmitis. This study summarises the results of 13 cases (3). 

It is nevertheless considered an ophthalmic allergen even though the percentage of detected cases did not exceed 2.1% (4).

Like all drugs it can cause side effects. Always ask the physician.

• Molecular Formula  C₆₀H₁₂₅N₁₅O₂₅S
• Molecular Weight  1488.8 g/mol   
• CAS  1405-41-0
• UNII    8X7386QRLV
• EC Number   215-778-9

References_____________________________________________________________________

(1) Jao, R.L. and Jackson, G.G., 1964. Gentamicin sulfate, new antibiotic against gram-negative bacilli: Laboratory, pharmacological, and clinical evaluation. Jama, 189(11), pp.817-822.

(2) Joseph, A. and Rustum, A., 2010. Development and validation of a RP-HPLC method for the determination of gentamicin sulfate and its related substances in a pharmaceutical cream using a short pentafluorophenyl column and a charged aerosol detector. Journal of pharmaceutical and biomedical analysis, 51(3), pp.521-531.

(3) Campochiaro, P.A. and Lim, J.I., 1994. Aminoglycoside toxicity in the treatment of endophthalmitis. Archives of ophthalmology, 112(1), pp.48-53.

Abstract. Objective and Methods:  Intravitreous aminoglycosides are widely used for the treatment and prophylaxis of endophthalmitis. Because the toxicity of 0.4 mg of gentamicin sulfate is well documented, many surgeons now use amikacin sulfate or low-dose gentamicin to reduce the risk of macular infarction. A survey of retinal specialists has suggested that amikacin or low-dose gentamicin can also cause macular toxic side effects. To further investigate this issue, the critical details of the case histories, findings, and course of 13 patients who received intravitreous injections of 0.2 to 0.4 mg of amikacin sulfate or 0.1 to 0.2 mg of gentamicin sulfate for prophylaxis or treatment of endophthalmitis are summarized. For several patients, complete case histories and a fluorescein angiogram are provided. Results:  These cases suggest that amikacin and low-dose gentamicin, similar to gentamicin sulfate at a dose of 0.4 mg, can cause macular infarction. The causative dose cannot be ascertained in any of the cases, but doses were prepared by hospital pharmacists using typewritten protocols, a practice that helps to prevent dilution errors. Several of these cases differ from previously reported cases of aminoglycoside toxicity in that the involvement of the macula was quite discrete. Most of the patients suffered severe visual loss, but two patients, in whom most of the nonperfusion was adjacent to the macula and in whom some of the perifoveal capillaries were spared, recovered 20/50 visual acuity. Conclusions:  These cases emphasize the potential hazards of the intravitreous use of aminoglycosides. A toxic reaction can occur even when injection of low doses is intended and precautions are made to avoid dilution errors. A localized increase in concentration in dependent areas of the retina may play a role in aminoglycoside toxicity. If some of the perifoveal capillaries are spared, retention of some central vision is possible. Consideration should be given to substituting ceftazidime for aminoglycosides for the treatment and prophylaxis of endophthalmitis.

(4) Herbst RA, Uter W, Pirker C, Geier J, Frosch PJ. Allergic and non-allergic periorbital dermatitis: patch test results of the Information Network of the Departments of Dermatology during a 5-year period. Contact Dermatitis. 2004 Jul;51(1):13-9. doi: 10.1111/j.0105-1873.2004.00334.x. 

Abstract. Periorbital dermatitis is common and can be due to the external use of ophthalmic drugs. We evaluated patch test results of the Information Network of the Departments of Dermatology. During a 5-year period (1995-99), of a total 49,256 patch-tested patients, 1053 (2.1%) were eventually diagnosed as allergic periorbital contact dermatitis (APD) and 588 (1.2%) as non-allergic periorbital dermatitis (NAPD). Patient characteristics between APD, NAPD and other cases (OCs) differed with respect to sex (19.7% male in both periorbital groups versus 36.3% in OCs), atopic dermatitis (10.4% in APD versus 60.2% in NAPD versus 16.9% in OCs) and age, APD being substantially more often (68.2%) aged 40 and above than NAPD (52.6%). Several of the top allergens in OCs [such as fragrance mix, Myroxylon pereirae resin (balsam of Peru), lanolin alcohol and potassium dichromate] caused significantly fewer positive test reactions in both periorbital groups. In contrast, thimerosal, phenylmercuric acetate, sodium disulfite, gentamicin sulfate, phenylephrine hydrochloride and benzalkonium chloride tested positively significantly more often in APD but not in NAPD, verifying them as true ophthalmic allergens. Finally, in 42 cases (4%) of APD patients, additional allergens were identified by testing of the patients' own substances (mostly beta-blockers, oxybuprocaine and dexpanthenol), supporting the necessity of testing with ophthalmic drugs as is where individual substances are not readily available.