A narrow therapeutic margin and poor predictability of plasma concentrations are the main reasons for drug level monitoring during aminoglycoside treatment. Gentamicin, tobramycin, amikacin and netilmicin can now be accurately and rapidly measured by radioenzymic, radio-immuno and enzyme-immuno assays. Routine determinations of peak (1-2 h post dose) and trough levels are recommended to ensure adequate dosage in all patients with serious Gram-negative infections, especially when renal function

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... s impaired. It should be realized, however, that maintaining aminoglycoside concentrations within a given range will only reduce, but not entirely eliminate the risk of toxicity. The pharmacokinetic behaviour of these antibiotics leads to a progressive drug accumulation in renal tissue and the inner ear, which depends both on dosage amd duration of treatment. 37