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Drug Details
Gentamicin 40 mg/ml Injection
- Drug Class Description
aminoglycoside antibiotic - Generic Name
gentamicin sulphate - Presentation
Solution for injection. Vials containing a clear colourless solution. - Description
1 ml of solution for injection contains 40 mg of gentamicin (as sulphate) 1 vial of 2 ml solution for injection contains 80 mg of gentamicin (as sulphate) - Indications
Gentamicin is bactericidal and is active against many strains of Gram-positive and Gram-negative pathogens including species of Escherichia, Enterobacter, Klebsiella, Salmonella, Serratia, Shigella, Staphylococcus aureus, some Proteus and against Pseudomonas aeruginosa. Gentamicin is often effective against strains of these organisms which are resistant to other antibiotics such as streptomycin, kanamycin and neomycin. Gentamicin is effective against penicillin-resistant Staphylococci, but rarely effective against Streptococci.
Gentamicin is indicated in the treatment of the following infections when caused by susceptible organisms.
Consideration should be given to official local guidance on the appropriate use of antibacterial agents
Severe Gram-Negative Infections:
Upper and lower urinary tract infections
Burn and wound infections
Septicaemia, Bacteraemia
Abscesses
Subacute Bacterial Endocarditis
Respiratory Tract infections (Bronchopneumonia)
Neonatal infections
Gynaecological infections
Gram-Positive Infections:
Bacteraemia
Abscesses
Accidental and operative trauma
Burns and serious skin lesions.
- Adult Dosage
Gentamicin is normally given by the intramuscular route, but can be given intravenously when intramuscular administration is not feasible.
Gentamicin is normally given by the intramuscular route, but can be given intravenously when intramuscular administration is not feasible, e.g. in shocked or severely burned patients. When given intravenously, the prescribed dose should be administered slowly over 2 to 3 minutes directly into a vein or into the rubber tubing of a giving set. Rapid, direct intravenous administration may give rise, initially, to potentially neurotoxic concentrations and it is essential that the prescribed dose is administered over the recommended period of time. Alternatively the prescribed dose should be dissolved in up to 100 ml of normal saline or 5% glucose in water, but not solutions containing bicarbonate (see Incompatibilities P6B, 7h), and the solution infused over a period of 20 to 30 minutes.
The same dosage schedule is recommended for intramuscular and intravenous dosing. Dosage is related to the severity of infection, the age of the patient and the patient's renal function.
The daily dose recommended in children, adolescents and adults with normal renal function, is 3-6 mg/kg body weight per day as 1 (preferred) up to 2 single doses.
The daily dose in infants after the first month of life is 4.5-7.5 mg/kg body weight per day as 1 (preferred) up to 2 single doses.
The daily dose in newborns is 4-7 mg/kg body weight per day. Due to the longer half-life, newborns are given the required daily dose in 1 single dose.
In impaired renal function, the recommended daily dose has to be decreased and adjusted to the renal function.
Doses in Patients with Impaired Renal Function:
Dosage is adjusted for patients with renal impairment to minimise the risk of toxicity. The first dose should be as normal - after this, doses should be given less frequently, the interval being determined by results of renal function tests as below:
Renal Function Tests:
Dose
Creatinine Clearance (ml/min)
Serum creatinine mmol/1
BUN mmol/1
Interval between doses
80 mg
over 70
less than
less than
8 hours
0.12
6.5
35-70
0.12-0.17
6.5-10
12 hours
24-34
0.18-0.25
11-14
18 hours
16-23
0.26-0.33
15-18
24 hours
10-15
0.34-0.47
19-26
36 hours
5-9
0.48-0.64
27-36
48 hours
Monitoring advice:
Serum concentration monitoring of gentamicin is recommended, especially in elderly, in newborns and in patients with impaired renal function. Samples are taken at the end of a dosing interval (trough level). Trough levels should not exceed 2 µg/ml administering gentamicin twice daily and 1 µg/ml for a once daily dose.
- Child Dosage
Up to two weeks, 3mg/kg every 12 hours; two weeks to 12 years, 2mg/kg every eight hours. - Contra Indications
Patients being treated with gentamicin should be under close clinical observation because of its potential toxicity.
Hypersensitivity to gentamicin, any other ingredient or other aminoglycosides.
Myasthenia gravis.
Gentamicin should be used with caution in premature infants because of their renal immaturity, in elderly people and generally in patients with impaired renal function. Diabetes, auditory vestibular dysfunctions, otitis media, a history of otitis media, previous use of ototoxic drugs and a genetically determined high sensitivity to aminoglycoside induced ototoxicity, are other main factors which may pre-dispose the patient to toxicity.
- Special Precautions
Patients being treated with gentamicin should be under close clinical observation because of its potential toxicity.
As with other aminoglycosides toxicity is related to serum concentration. At serum levels more than 10 micrograms/ml the vestibular mechanism may be affected. Toxicity can be minimised by monitoring serum concentrations and it is advisable to check serum levels to confirm that peak levels (one hour) do not exceed 10 micrograms/ml and that trough levels (one hour before next injection) do not exceed 2 micrograms/ml when administering Gentamicin twice daily and 1µg/ml for a once daily dose. Evidence of toxicity requires adjustment of dosage or withdrawal of the drug.
Concurrent use of other neurotoxic and/or nephrotoxic drugs can increase the possibility of gentamicin toxicity. Co-administration with the following agents should be avoided:
Neuromuscular blocking agents such as succinylcholine and tubocurarine.
Other potentially nephrotoxic or ototoxic drugs such as cephalosporins and methicillin.
Potent diuretics such as ethacrynic acid and furosemide.
Other aminoglycosides.
To avoid adverse events, continuous monitoring (before, during and after) of renal function (serum creatinin, creatinin clearance), control of function of vestibule and cochlea as well as hepatic and laboratory parameters is recommended.
Sulphites can cause allergic-type reactions including anaphylactic symptoms and bronchospasm in susceptible people, especially those with a history of asthma or allergy.
- Interactions
(i) Antibacterials: increased risk of nephrotoxicity with cephalosporins notably cephalothin .
(ii) Gentamicin has been known to potentiate anticoagulants such as warfarin and phenindione.
(iii) Antifungals: increased risk of nephrotoxicity with amphotericin.
(iv) Cholinergics: antagonism of effect of neostigmine and pyridostigmine.
(v) Cyclosporin: increased risk of nephrotoxicity.
(vi) Cytotoxics: increased risk of nephrotoxicity and possible risk of ototoxicity with cisplatin.
(vii) Diuretics: increased risk of ototoxicity with loop diuretics.
(viii) Muscle relaxants: effect of non-depolarising muscle relaxants such as tubocurarine enhanced.
- Adverse Drug Reactions
Ototoxicity and nephrotoxicity are the most common side effects associated with Gentamicin therapy. Both effects are related to renal impairment and hence the dosage in such patients should be altered as suggested. In addition, there have been rare reports of changes in electrolyte balance including hypocalcaemia and hypokalaemia caused by renal tubular dysfunction.
Vestibular damage and ototoxicity may occur. This is usually reversible if observed promptly and the dose adjusted.
Other adverse reactions associated with Gentamicin therapy include nausea, vomiting, urticaria, reversible granulocytopenia, allergic contact sensitisation and neuromuscular blockade. There have been a few reports of anaphylactic reactions associated with gentamicin containing therapy.
Combinations of antibiotics containing gentamicin have been associated with rare reports of Clostridium difficile diarrhoea.