4.1. Therapeutic indications

Gentamicin is indicated in adolescents, children and adults for the following:

The treatment of systemic infections due to susceptible bacteria such as, bacteraemia, septicaemia, urinary-tract infections and severe chest infections.

Consideration should be given to official local guidance on the appropriate use of antibacterial agents.

4.2. Posology and method of administration

Posology

Adults

The daily recommended dose in adults with normal renal function is 3-6mg/kg body weight per day as one (preferred) up to two single doses.

Serious infections

In life-threatening infections the frequency of dosage may need to be increased to 6-hourly and the quantity of each dose may also be increased at the discretion of the clinician up to a total dosage of 5mg/kg in 24 hours. In such cases it is advisable to monitor gentamicin serum levels.

If renal function is not impaired, 160mg once daily may be used in some cases.

Renal impairment

In cases of impaired renal function a reduction in dosage frequency is recommended. The following table is a guide to recommended dosage schedules:

Blood urea

(mg/100ml)

Creatinine clearance (GFR) (ml/min)

Dose and frequency of administration

<40

40 - 100

100 - 200

>200

Twice-weekly intermittent haemodialysis

>70

30 - 70

10 - 30

5 - 10

<5

80mg† 8-hourly

80mg† 12-hourly

80mg† daily

80mg† every 48 hours

80mg† after dialysis

† 60mg if body weight <60kg

Paediatric population:

The daily recommended dose in children and adolescents with normal renal function is 3-6mg/kg body weight per day as one (preferred) up to two single doses.

The daily dose in infants after the first month of life is 4.5-7.5mg/kg body weight per day as one (preferred) up to two single doses.

The daily dose in newborns is 4-7mg/kg body weight per day. Due to the longer half-life, newborns are given the required daily dose in one single dose.

Method of administration:

Gentamicin is normally administered intramuscularly but may be given intravenously as a slow intravenous injection over at least 3 minutes or short infusion if required. Gentamicin should not be given as a slow infusion or mixed with other drugs before use (see Incompatibilities).

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 2µg/ml administering gentamicin twice daily and 1µg/ml for a once daily dose.

Prolonged use should be avoided and whenever possible the treatment should not exceed 7 days.

Caution is advised in significant obesity as gentamicin is poorly distributed into fatty tissue. The dosage calculation should be based on an estimate of lean body weight. Serum levels should be monitored closely and the dose possibly adjusted (see 4.4).

4.3. Contraindications

Hypersensitivity to the active substance or to any of the excipients listed in section 6.1 or to other aminoglycosides.

Myasthenia gravis.

4.4. Special warnings and precautions for use

To avoid adverse events, continuous monitoring (before, during and after) of renal function (serum creatinine, creatinine clearance), control of function of vestibule and cochlea as well as hepatic and laboratory parameters is recommended.

Where renal function is impaired through disease or old age the frequency, but not the amount, of each dose should be reduced according to the degree of impairment. Gentamicin is excreted by simple glomerular filtration, and dosage frequency may be predicted by assessing serum creatinine, creatinine clearance rates or blood urea and reducing the frequency accordingly. Volume depletion or hypotension and liver disease have been reported as additional risk factors for nephrotoxicity. In some patients with impaired renal function there has been a transient rise in blood-urea-nitrogen which has usually reverted to normal during or following cessation of therapy. It is important to adjust the frequency of dosage according to the degree of renal function.

Ototoxicity has been recorded following the use of gentamicin. Impaired hepatic function or auditory function, bacteraemia and fever have been reported to increase the risk of ototoxicity. Groups at special risk include patients with impaired renal function, infants and possibly the elderly. Consequently, renal, auditory and vestibular functions should be monitored in these patients and serum levels determined so as to avoid peak concentrations above 10mg/l and troughs above 2mg/l when administrating Gentamicin twice daily and 1mg/l for a once daily dose. As there is some evidence that risk of both ototoxicity and nephrotoxicity is related to the level of total exposure, duration of therapy should be the shortest possible compatible with clinical recovery.

There is an increased risk of ototoxicity in patients with mitochondrial DNA mutations (particularly the nucleotide 1555 A to G substitution in the 12S rRNA gene), even if aminoglycoside serum levels are within the recommended range during treatment. Alternative treatment options should be considered in such patients.

In patients with a maternal history of relevant mutations or aminoglycoside induced deafness, alternative treatments or genetic testing prior to administration should be considered. Mitochondrial mutations are rare, and the penetrance of this observed effect is unknown.

Caution is required in Parkinsonism and other conditions characterised by muscular weakness.

In cases of significant obesity gentamicin serum concentrations should be closely monitored and a reduction in dose should be considered (see section 4.2).

Gentamicin should only be used in pregnancy if considered essential by the physician (see section 4.6).

Treatment with gentamicin may produce an excessive growth of drug-resistant microorganisms. If this happens, an appropriate treatment should be initiated.

Diarrhoea and pseudomembranous colitis have been observed when gentamicin is combined with other antibiotics. These diagnoses should be considered in every patient that develops diarrhoea during or immediately after treatment. Gentamicin should be discontinued if the patient suffers severe diarrhoea and/or bloody diarrhoea during treatment and an appropriate treatment should be initiated. Drugs that inhibit peristalsis should not be administered (see section 4.8).

4.5. Interaction with other medicinal products and other forms of interaction

Gentamicin should not be used concurrently with other potentially nephrotoxic or ototoxic drug substances unless considered essential by the physician. The potential nephrotoxicity of other aminoglycosides, vancomycin, ciclosporin, cisplatin, fludarabine and amphotericin may be increased in the presence of gentamicin and monitoring of renal function is therefore recommended.

Any potential nephrotoxicity of cephalosporins, and in particular cephaloridine, may also be increased in the presence of gentamicin. Consequently, if this combination is used monitoring of kidney function is advised.

Furosemide (frusemide) and piretanide may potentiate the ototoxicity of gentamicin, and etacrynic acid, which is ototoxic in its own right, should be avoided with gentamicin.

Aminoglycosides, including gentamicin, may induce neuromuscular blockade and respiratory paralysis and should therefore only be used with great caution in patients receiving curare-type muscle relaxants.

Aminoglycosides antagonise the effects of cholinergic agents such as neostigmine and pyridostigmine.

Indometacin has been reported to increase the plasma concentrations of aminoglycosides when given concomitantly.

Concurrent use with oral anticoagulants may increase the hypothrombinanaemic effect.

Concurrent use of bisphosphonates may increase the risk of hypocalcaemia.

Concurrent use of the Botulinum Toxin and gentamicin may increase the risk of toxicity due to enhanced neuromuscular block.

Bacteriostatic antibiotics may give an antagonistic interaction, but in some cases (e.g. with clindamycin and lincomycin) the disadvantage of antagonism may be outweighed by the addition of activity against anaerobic organisms. Synergistic action has been demonstrated with penicillin. However, if penicillins (such as ticarcillin) are used with gentamicin the drugs should not be physically mixed and patients with poor renal function should be monitored for effectiveness of the gentamicin. Cross-sensitivity with aminoglycosides may occur.

4.6. Fertility, pregnancy and lactation

Pregnancy

Safety for use in pregnancy has not been established. Gentamicin crosses the placenta and there is a risk of ototoxicity (auditory or vestibular nerve damage) in the foetus. Gentamicin should only be used where the seriousness of the mother's condition justifies the risk and use is considered essential by the physician. In such cases, serum gentamicin concentration monitoring is essential. Some animal studies have shown a teratogenic effect.

Breast-feeding

Gentamicin is excreted in breast milk, but is unlikely to be a hazard to the infant except in the presence of maternal renal insufficiency when breast-feeding should be avoided, as the levels in breast milk then rise appreciably. In the absence of gastro-intestinal inflammation, the amount of gentamicin ingested from the milk is unlikely to result in significant blood levels in breast-fed infants.

Fertility

No data available

4.7. Effects on ability to drive and use machines

This medicine has no or negligible influence on the ability to drive and use machines.

4.8. Undesirable effects

As with all aminoglycosides, at critical levels gentamicin exhibits toxicity. The following undesirable effects have been reported for gentamicin. The undesirable effects are listed according to their frequency:

Common (≥1/100 to <1/10)

Uncommon (≥1/1,000 to <1/100)

Rare (≥1/10,000 to <1/1,000)

Very rare (<1/10,000)

Not known (cannot be estimated from the available data)

System Organ Class

Frequency

Adverse reaction

Infections and infestations

Not known

Superinfection (caused by gentamicin-resistant bacteria)

Pseudomembranous colitis1

Blood and lymphatic system disorders

Uncommon

Not known

Blood disorder

Anaemia

Immune system disorders

Not known

Anaphylactic reaction (including anaphylactic shock) and hypersensitivity

Metabolism and nutrition disorders

Rare

Electrolyte imbalance (e.g. hypomagnesaemia, hypocalcaemia and hypokalaemia)

Psychiatric disorders

Very rare

Confusional state, hallucination and depression

Nervous system disorders

Common

Very rare

Neuromuscular blockade2

Encephalopathy, seizure

Ear and labyrinth disorders

Not known

Irreversible hearing loss, deafness

Vascular disorders

Not known

Purpura

Gastrointestinal disorders

Uncommon

Nausea, vomiting, stomatitis.

Skin and subcutaneous tissue disorders

Not known

Steven Johnson syndrome, Toxic epidermal necrosis.

Rash

Renal and urinary disorders

Very rare

Not known

Acute renal failure, Fanconi-like syndrome in patients treated with a prolonged course of high-dose

Nephropathy toxic 3,

General disorders and administration site conditions

Very rare

Lethargy

Investigations

Uncommon

Aspartate/alanine aminotransferase increased, blood bilirubin increased

1 usually in these cases other antibiotics are also involved.

2 Gentamicin can cause neuromuscular blockade which may unmask or aggravate myasthenia gravis and cause postoperative respiratory distress.

3 Nephrotoxicity may occur, resulting in a gradual reduction in creatinine clearance after several days of treatment. This is usually reversible if the drug is withdrawn. Nephrotoxicity is more common if trough serum concentrations exceed 2 micrograms/ml and where there is pre-existing renal disease or concomitant treatment with other nephrotoxic agents.

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 Website: www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store.

4.9. Overdose

Symptoms

Symptoms include dizziness, vertigo and hearing loss if overdose accidentally given parenterally.

Management

If the reaction is severe consider haemodialysis as treatment. Gentamicin may be removed from the body by haemodialysis or peritoneal dialysis. Calcium salts given intravenously have been used to counter the neuromuscular blockade caused by gentamicin.