Posology : מינונים

4.2 Posology and method of administration

Adults:
Systemic infections: if renal function is not impaired, 3-5 mg/kg/day in divided doses according to severity of infection, adjusting according to clinical response and body weight.
Serious infections: if renal function is not impaired, 5mg/kg daily in divided doses at six or eight hourly intervals. The total daily dose may be subsequently increased or decreased as clinically indicated.
Urinary tract infections: as 'systemic infections'. Or, if renal function is not impaired, 160mg once daily may be used.
Paediatric Patients:


The daily dose recommended in children (aged 1 year and above) and adolescents with normal renal function, is 3-6 mg/kg body weight per day as 1 single dose (preferred) or 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 single dose (preferred) or up to 2 single doses.
The daily dose in neonates is 4-7 mg/kg body weight per day. Due to the longer half-life, neonates are given the required daily dose in 1 single dose.
Elderly:
There is some evidence that elderly patients may be more susceptible to aminoglycoside toxicity whether secondary to previous eighth nerve 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 toxicity.
Renal impairment:
Gentamicin is excreted by simple glomerular filtration. In impaired renal function, the recommended daily dose has to be decreased and adjusted to the renal function.
Nomograms are available for the calculation of the dose, which depends on the patient's age, weight, and renal function.
The following table may be useful when treating adults:
Blood urea                               Creatinine clearance Dose and frequency (mg/100ml)       (mmol/I)                (GFR) (ml/min)       of administration <40              6-7                     >70                     80mg* 8- hourly 40-100           6-17                    30-70                   80mg* 12- hourly
100-200          17-34                   10-30                   80mg* daily >200             >34                     5-10                    80mg* every 48 hours Twice- weekly intermittent               <5                      80mg* after dialysis haemodialysis


*60mg if body weight <60kg. Frequency of dosage in hours may also be approximated as serum creatinine (mg%) x eight or in SI units, as serum creatinine (μmol/l) divided by 11.
If these dosage guides are used, peak serum levels must be measured. Peak levels of gentamicin occur approximately one hour after intramuscular injection and intravenous injection. Trough levels are measured just prior to the next injection. Assay of peak serum levels gives confirmation of adequacy of dosage and also serves to detect levels above 10mg/l, at which the possibility of ototoxicity should be considered. One hour concentrations of gentamicin should not exceed 10mg/l (but should reach 4mg/l), while the pre-dose trough concentration should be less than 2mg/l.
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 100ml. 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.


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. Please refer to section 4.4.