Antibiotic Dosing in CKD Pregnancy: There are limited data from the use of aminoglycosides, including gentamicin, in pregnancy. Gentamicin crosses the placenta and there is a risk of ototoxicity (vestibulocochlear nerve damage) and/or renal damage in the foetus, as seen in animal studies. Gentamicin should NOT be used in pregnancy, except in life-threatening situations where expected benefits outweigh possible risks; in such cases maternal serum gentamicin concentration monitoring is recommended, as is monitoring of the hearing and renal function of the infant. Breast-feeding: gentamicin is excreted in human breast milk and has been detected in low concentrations in the serum of breast-fed infants, except where the infant's gastrointestinal mucous membrane is severely eroded — in suspected severe mucosal erosion, monitoring of the infant's serum gentamicin concentration is recommended, and animal and human data suggest that if the infant's serum concentration exceeds 1 microgram/mL either breast-feeding or gentamicin therapy may need to be discontinued under medical supervision. Monitor the infant for effects on normal gastrointestinal flora such as diarrhoea, candidiasis and bloody stools.

Gentamicin (Renal Dosing/TDM)

Brand names: Cidomycin

Gentamicin in the renal-dosing and therapeutic drug monitoring (TDM) context is an aminoglycoside antibiotic for serious Gram-negative infection; its narrow therapeutic index and renal elimination make dose individualisation and level monitoring essential, especially in CKD.

Adult dose

Dose: 3 - 5 mg/kg/day in adults with normal renal function, depending on the severity of infection. Dose calculations should be based on IDEAL BODY WEIGHT

Route: Intravenous or intramuscular — the recommended dose and precautions for both routes are identical. Given intravenously it should be injected directly into a vein or into the drip set tubing over no less than three minutes; if given by infusion, over 20 - 30 minutes in no greater volume of fluid than 100 mL (longer infusion times 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

Frequency: As one single daily dose (preferred) or in two divided doses, adjusted according to clinical response and serum concentration levels

Source: UK SPC (eMC) for Cidomycin 80mg/2ml Solution for Injection, section 4.2 (https://www.medicines.org.uk/emc/product/14742/smpc). A dosing frequency of more than twice daily may be adopted for some specific pathogens or 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. URINARY TRACT INFECTION: in patients with normal renal function, 160 mg once daily may be used. GENTAMICIN SHOULD NOT BE PRESCRIBED IF SERUM CONCENTRATIONS CANNOT BE MONITORED. THERAPEUTIC DRUG MONITORING (section 4.2): regular serum concentration monitoring is recommended for all patients, and especially in the elderly, newborns, obesity, impaired renal function and cystic fibrosis. There are no universally accepted guidelines for TDM of gentamicin, and local monitoring and dose adjustment guidelines should be followed where available. PRE-DOSE ('trough') monitoring is recommended to ensure the interval between doses is correct; troughs 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 to reduce the dose. POST-DOSE ('peak') monitoring is recommended to check the adequacy of a dose or that it is not excessive; peaks should be measured one hour after an intravenous or intramuscular bolus dose, or 30 minutes after the end of an infusion. A plasma concentration below 4 mg/L indicates the dose is likely to be inadequate and a dose increase should be considered; concentrations above 10 mg/L indicate an increased risk of 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. SAFETY (section 4.4): ototoxicity (loss of balance and hearing loss, which may be irreversible) and nephrotoxicity are the key risks; important risk factors include renal impairment, high doses, prolonged duration of treatment and age (neonates/infants and possibly the elderly). Monitoring of vestibule, cochlea and renal function is recommended before, during and shortly after treatment. Because risk relates to 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 when serum levels are within range — alternative treatment options should be considered in such patients, and in patients with a maternal history of relevant mutations or aminoglycoside-induced deafness, alternative treatments or genetic testing prior to administration should be considered. In significant obesity, serum concentrations should be closely monitored and a dose reduction considered. Gentamicin should be used with care in conditions characterised by muscular weakness. SOURCE LIMITATION: eMC section 4.5 was NOT captured in this bundle and the openFDA/US label retrieved contains no drug interactions section — NO interactions list is therefore given below and section 4.5 must be checked on the SPC. Some sections of the product information we used were incomplete — check the full SPC.

Paediatric dose

Route: Intravenous or intramuscular (once daily dosing should only be given intravenously)

Frequency: As one single daily dose (preferred) or in two divided doses; newborns are given the required daily dose in one single dose due to the longer half-life

Max: No maximum dose is stated for the paediatric population in section 4.2

dosePerKg is left null because the SPC states RANGES by age band, not a single per-kg value, and all values are DAILY totals, not per-dose figures. Section 4.2 verbatim bands: children aged 1 year and above and adolescents with normal renal function — 3 to 6 mg/kg/day as one single dose (preferred) or two divided doses; infants after the first month of life — 4.5 to 7.5 mg/kg/day as one single dose (preferred) or two divided doses; neonates and pre-term infants (aged 0 to 4 weeks old) — 4 to 7 mg/kg/day, given as one single dose because of the longer half-life. Peri-operative prophylaxis and renal adjustment principles for children are not separately tabulated in this SPC; serum level monitoring is specifically recommended in newborns. Verify all paediatric dosing against a children's formulary.

Dose adjustments

Renal

In impaired renal function the recommended daily dose HAS TO BE DECREASED and adjusted to renal function, achieved by reducing the dose and/or increasing the dose interval. In all patients with renal impairment, serum gentamicin peak and trough concentrations and renal function must be monitored frequently. Nomograms are available for calculating the 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 in renal impairment — dosing should be guided by plasma concentration levels. In moderate renal impairment, where once daily dosing would be considered appropriate if renal function were normal, the dose interval should be AT LEAST 24 HOURS and extended according to the degree of renal impairment and serum gentamicin monitoring. Limited data are available in patients with severe renal impairment (creatinine clearance below 30 mL/min) after once daily dose administration. SPC TABLE FOR ADULTS ON MULTIPLE DAILY DOSE REGIMENS (blood urea mg/100 mL; urea mmol/L; creatinine clearance mL/min; dose and frequency) — below 40; 6-7; above 70: 80 mg 8 hourly. 40-100; 6-17; 30-70: 80 mg 12 hourly. 100-200; 17-34; 10-30: 80 mg daily. Above 200; above 34; 5-10: 80 mg every 48 hours. Twice weekly intermittent haemodialysis; creatinine clearance below 5: 80 mg after dialysis. In every row, use 60 mg instead of 80 mg if body weight is under 60 kg. It is important to adjust the FREQUENCY of dosage according to the degree of renal function; in some patients with impaired renal function there has been a transient rise in blood urea nitrogen which usually reverts to normal during or after cessation of therapy.

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance or to any of the excipients
Myasthenia gravis

Side effects

Ear and labyrinth (frequency not known): vestibular damage, transitory hearing loss, irreversible hearing loss and deafness, particularly after exposure to ototoxic drugs or in the presence of renal dysfunction
Renal and urinary: acute renal failure and Fanconi-like syndrome (very rare, in patients treated with a prolonged course of high dose); nephrotoxicity, usually reversible, reported with frequency not known
Gastrointestinal: vomiting (very common); nausea and stomatitis (frequency not known); antibiotic-associated colitis including pseudomembranous colitis
Nervous system (frequency not known): central neuropathy including convulsions, lethargy and encephalopathy; peripheral neuropathy; psychiatric — depression, hallucinations, confusion
Hypersensitivity and anaphylaxis/anaphylactic reaction including anaphylactic shock; skin — Stevens-Johnson syndrome, toxic epidermal necrolysis, rash, purpura, urticaria, pruritus
Other: hypomagnesaemia on prolonged therapy; anaemia and blood dyscrasias; abnormal liver function and increased transaminases; superinfection caused by gentamicin-resistant bacteria

Clinical monograph

How it works

It binds the 30S bacterial ribosomal subunit to inhibit protein synthesis, producing concentration-dependent bactericidal activity against susceptible organisms.

Prescribing in practice

Nephrotoxicity and irreversible ototoxicity are the dominant risks, so dose by weight and renal function and use therapeutic drug monitoring to guide dosing and intervals.
Extend the dosing interval rather than simply cutting the dose in renal impairment, and check levels before deciding subsequent doses.
Avoid where possible in combination with other nephrotoxins or ototoxins, and review the need to continue daily.

Monitoring

Monitor renal function and gentamicin concentrations (peak and/or trough as per local protocol) to keep levels in the therapeutic range and pre-empt toxicity.

Counselling the patient

Blood tests to measure drug levels and kidney function are needed during treatment.
Report any hearing loss, ringing in the ears, dizziness or balance problems immediately.
Tell the team about all other medicines, as some increase the risk to kidneys and hearing.

Evidence & guidelines

UK antimicrobial guidance and NICE recommend weight- and renal-function-based aminoglycoside dosing with mandatory therapeutic drug monitoring.

Reference: Hartford Nomogram; NICE NG15 (Antimicrobial Stewardship); PHE Guidelines; SPC Cidomycin; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

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