Gentamicin is an aminoglycoside antibiotic with broad-spectrum bactericidal activity. It is
indicated to treat severe infections caused by bacteria susceptible to gentamicin such as, but not
limited to:
• Urinary tract infections
• Respiratory tract infections
• Intra-abdominal infections
• CNS infections
• Severe neonatal infections
It is usually active against most strains of the following organisms: Escherichia coli, Klebsiella
spp., Proteus spp. (indole positive and indole negative), Pseudomonas
aeruginosa, Staphylococci, Enterobacter spp., Citrobacter spp. and Providencia spp.

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

Adults
The recommended dose in adults with normal renal function is 3 – 5 mg/kg/day, depending on
the severity of infection, administered as one single dose (preferred) or in two divided doses. The
dose should be adjusted according to clinical response and serum concentration levels (see
below). Dose calculations should be based on ideal body weight. A dosing frequency of more
than twice daily may be adopted for some specific pathogens or some sites of infection as
recommended in national and local guidance.
Once daily dosing is not recommended in cases of endocarditis, depending on the responsible
pathogens. National and local guidance on treatment with gentamicin and serum level
monitoring in endocarditis should be followed.
In patients with normal renal function, 160 mg once daily may be used for the treatment of
urinary tract infections.
Paediatric population
The daily dose recommended in children aged 1 year and above and adolescents with normal
renal function, is 3 – 6 mg/kg/day as one single dose (preferred) or two divided doses.
The daily dose in infants after the first month of life is 4.5 – 7.5 mg/kg/day as one single dose
(preferred) or two divided doses.
The daily dose in neonates and pre-term infants (aged 0 – 4 weeks old) is 4 – 7 mg/kg/day. Due
to the longer half-life, newborns are given the required daily dose in one single dose.
Elderly
There is some evidence that elderly patients may be more susceptible to aminoglycoside toxicity
whether secondary to previous auditory/vestibular impairment or borderline renal dysfunction.
Accordingly, therapy should be closely monitored by frequent determination of gentamicin
serum levels, assessment of renal function and signs of ototoxicity.
Renal impairment
In impaired renal function, the recommended daily dose has to be decreased and adjusted to the
renal function. This can be achieved by reducing the dose and/or increasing the dose interval.
In all patients with renal impairment, serum gentamicin peak and trough concentration and renal
function must be monitored frequently (see below).
Nomograms are available for the calculation of dose, which depends on the patient's age, weight
and renal function. Local guidance should be followed where available.
No clear recommendation can be made for once daily dosing; dosing should be guided by plasma
concentration levels. In patients with moderate renal impairment, in whom once daily dosing

would be considered appropriate if their renal function were normal, the dose interval should be
at least 24 hours and extended according to the degree of renal impairment and the results of
serum gentamicin monitoring. Limited data are available in patients with severe renal
impairment (creatinine clearance < 30 ml/min) after once daily dose administration.
The following table may be useful for adults on multiple daily dose regimens:

*60 mg if body weight < 60 kg.
Monitoring advice
Regular serum concentration monitoring of gentamicin is recommended for all patients, and
especially in the elderly, newborns, obesity and in patients with impaired renal function, as well
as patients with cystic fibrosis. Gentamicin should not be prescribed if serum concentrations
cannot be monitored.
There are no universally accepted guidelines for therapeutic drug monitoring of gentamicin.
Local monitoring and dose adjustment guidelines should be followed where available.
Pre-dose (“trough level”) monitoring is recommended to ensure that the interval between doses
is correct. Trough levels are measured at the end of a dosing interval and should not exceed 1
mg/L for once daily dosing or 2 mg/L for multiple daily dosing. Levels in excess of these
indicate the need to extend the interval between doses, not reduction of the dose.
Post-dose (“peak level”) monitoring is recommended to check the adequacy of a dose or to
ensure that it is not excessive and likely to cause toxicity. Peak levels should be measured one
hour after an intravenous bolus or intramuscular bolus dose, or 30 minutes after the end of an
infusion. A plasma concentration < 4 mg/L indicates that the dose is likely to be inadequate and a
dose increase should be considered; plasma concentrations > 10 mg/L indicate an increased risk
for toxicity, particularly ototoxicity, and a dose reduction should be considered.
Any change in dose should be re-assessed with pre- and post-dose levels to confirm the adequacy
of the new dose and the appropriateness of the dose interval.
Method of administration
The recommended dose and precautions for intramuscular and intravenous administration are
identical. Gentamicin when given intravenously should be injected directly into a vein or into the
drip set tubing over no less than three minutes. If administered by infusion, this should be over
20 – 30 minutes and in no greater volume of fluid than 100 ml. Longer infusion times of up to 60
minutes may be used, in particular for a once daily dosing regimen. Once daily dosing should
only be administered through the intravenous route.

Ototoxicity and nephrotoxicity
Ototoxicity has been reported following the use of aminoglycosides, including gentamicin.
Symptoms include loss of balance and hearing loss, which may be irreversible (see section 4.8).
Important risk factors include renal impairment, high doses, prolonged duration of treatment and
age (neonates/infants and possibly the elderly). Due to the potential for ototoxicity and
nephrotoxicity, monitoring of vestibule, cochlea and renal function is recommended before,
during and shortly after treatment (see section 4.8). Serum levels are determined so as to avoid
peak concentrations above 10 mg/L and troughs above 1 mg/L when administering gentamicin
once daily and 2 mg/L when administering gentamicin twice daily.
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. In some patients with impaired renal function there has been a transient rise in bloodurea-
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.
To avoid adverse events, continuous monitoring (before, during and after treatment) of hepatic
and laboratory parameters is also recommended.
Gentamicin should only be used in pregnancy if considered essential by the physician (see
section 4.6).
Gentamicin should be used with care in 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.

Concurrent administration of gentamicin and other potentially ototoxic or nephrotoxic drugs
should be avoided. Potent diuretics such as etacrynic acid and furosemide are believed to
enhance the risk of ototoxicity whilst amphotericin B, cisplatin and ciclosporin are potential
enhancers of nephrotoxicity.
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.
Neuromuscular blockade and respiratory paralysis have been reported from administration of
aminoglycosides to patients who have received curare-type muscle relaxants during anaesthesia.
Indometacin possibly increases plasma concentrations of gentamicin in neonates.
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.
Antagonism of effect may occur with concomitant administration of gentamicin with either
neostigmine or pyridostigmine.

Pregnancy
There are no proven cases of intrauterine damage caused by gentamicin. However, in common
with most drugs known to cross the placenta, usage in pregnancy should only be considered in
life threatening situations where expected benefits outweigh possible risks.
Breast-feeding
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.

Not known.

The following CIOMS frequency rating is used, when applicable: Very common (≥ 1/10);
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).
Infections and infestations:
Not known: antibiotic-associated colitis
Blood and lymphatic system disorders:
Not known: anaemia, blood dyscrasias
Immune system disorders:
Not known: hypersensitivity, anaphylaxis/anaphylactic reaction (including anaphylactic shock)
Metabolism and nutrition disorders:
Not known: hypomagnesaemia on prolonged therapy
Psychiatric disorders:
Not known: depression, hallucinations, confusion
Nervous system disorders:
Not known: central neuropathy (including convulsions, lethargy, encephalopathy), peripheral
neuropathy
Ear and labyrinth disorders:

Not known: vestibular damage, transitory hearing loss, irreversible hearing loss, deafness,
particularly after exposure to ototoxic drugs or in the presence of renal dysfunction (see section
4.4).
Gastrointestinal disorders:
Very common: vomiting
Not known: stomatitis, nausea
Hepatobiliary disorders:
Not known: abnormal liver function, transaminases increased
Skin and subcutaneous tissue disorders:
Not known: rash, purpura, urticaria, pruritus
Renal and urinary disorders:
Very rare: acute renal failure, Fanconi-like syndrome in patients treated with a prolonged course
of high-dose
Not known: nephrotoxicity (usually reversible) has been reported.
Reporting of suspected adverse reactions
Reporting suspected adverse reactions after authorization 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:

Haemodialysis and peritoneal dialysis will aid the removal from blood but the former is probably
more efficient. Calcium salts given intravenously have been used to counter the neuromuscular
blockade caused by gentamicin.

Pharmacotherapeutic group: Antibacterials for systemic use ATC Code: J01GB03

Gentamicin is a mixture of antibiotic substances produced by the growth of micromonospora
purpurea. It is bactericidal with 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 its most important effects is inhibition of
protein synthesis at the level of the 30s ribosomal subunit.

Gentamicin is not readily absorbed from the gastro-intestinal tract. Gentamicin is 70 – 85%
bound to plasma albumin following administration and is excreted 90% unchanged in urine. The
half-life for its elimination in normal patients is 2 – 3 hours.
• Effective plasma concentration is 4 – 8 μg/ml.
• The volume of distribution (vd) is 0.3 l/kg.
• The elimination rate constant is:
1. 0.02 hr-1 for anuric patients*
2. 0.30 hr-1 normal
* Therefore in those with anuria care must be exercised following the usual initial dose, any
subsequent administration being reduced in-line with plasma concentrations of gentamicin.
Paediatric population (premature infants and neonates)
Distribution
The distribution volume of gentamicin is about equivalent to the volume of extracellular water.
In the newborn water makes up 70 – 75% of bodyweight, compared with 50 – 55% in adults. The
extracellular water compartment is larger (40% of body weight compared with 25% of body
weight in adults). Therefore, the volume of distribution of gentamicin per kg bodyweight is
affected and decreases with increasing age from 0.5 – 0.7 l/kg for a premature newborn to 0.25
l/kg for an adolescent. The larger volume of distribution per kg bodyweight means that for
adequate peak blood concentration a higher dose per kg bodyweight needs to be administered.
Elimination
Gentamicin is not metabolized in the body but is excreted unchanged in microbiologically active
form predominantly via the kidneys. In patients with normal renal function the elimination halflife
is about 2 – 3 hours. In neonates elimination rate is reduced due to immature renal function.
Elimination half-life averages approximately 8 hours in neonates at a gestational age of 26 – 34
weeks compared with about 6.7 hours in neonates at a gestational age of 35 – 37 weeks.
Correspondingly, clearance values increase from about 0.05 l/h in neonates at a gestational age
of 27 – 0.2 l/h in neonates at a gestational age of 40 weeks.

Not applicable particulars

Methylparahydroxybenzoate,
Propylparahydroxybenzoate,
Disodium Edetate &
Water for Injection.

In general, gentamicin injection should not be mixed.
In particular, the following are incompatible in mixed solution with gentamicin injection:
− penicillins
− cephalosporins
− erythromycin
− heparins
− sodium bicarbonate
*Dilution in the body will obviate the danger of physical and chemical incompatibility and
enable gentamicin to be given concurrently with the drugs listed above either as a bolus injection
into the drip tubing, with adequate flushing, or at separate sites. In the case of carbenicillin,
administration should only be at a separate site.
*Carbon dioxide may be liberated on addition of the two solutions. Normally this will dissolve in
the solution but under some circumstances small bubbles may form.

Do not store above 25°C. Do not refrigerate or freeze.

Gentam 20mg is supplied in tubular 2ml clear glass ampoules with blue identification ring code
and pre-scored constriction for easy breaking.
Gentam 80mg is supplied in tubular 2ml clear glass ampoules with a red identification ring
code and pre-scored constriction for easy breaking.

No Special Requirements