Prescribing aids for gentamicin.

1 A nomogram and a digital computer program have been developed to calculate dosage schedules of gentamicin for individual patients. The minimum input data consist of the patients' age, sex, body weight and serum creatinine concentration. 2 These prescribing aids have been evaluated in 36 patients with severe Gram negative infections. Renal function ranged from normal to complete anuria. Nomogram dosage schedules gave serum concentrations of gentamicin within the chosen therapeutic limits. Physician dosage schedules gave serum concentrations which sometimes exceeded and sometimes fell below these limits. The validity of the computer program was demonstrated by its ability to predict serum concentrations of gentamicin whatever the dosage schedule. 3 Half the patients recovered from the bacterial infection but seven remained infected and eleven died. Pseudomonas aeruginosa was the most difficult organism to eradicate. 4 Four of the patients who survived developed ataxia and two developed hearing loss at high frequencies. The risk of ototoxicity was a function of mean trough serum gentamicin concentration and duration of treatment. Ototoxicity was only detected in patients with serum creatinine concentrations above 3 mg/100 ml who tended to have higher trough concentrations. When treatment was prolonged beyond 8-10 days the risk of ototoxicity was increased without evidence of further substantial therapeutic benefit.