Why Monitor Serum Levels of Gentamicin?

Abstract

Although it is widely recommended that serum levels of aminoglycoside antibiotics be monitored by assay, the justification for this approach has not been clearly presented. A number of studies indicate that serum levels of these agents cannot be predicted reliably on the basis of simple dosage formulae; the major confounding factors being abnormalities of renal function and of extracellular fluid volume in addition to less well defined variables such as fever and anaemia. The influence of haemodialysis and concomitant administration of carbenicillin further complicate dosage estimations in patients with renal insufficiency. On the basis of currently available data, it is reasonable to suggest an optimum range of 5 to 8 microgram/ml for peak serum levels of gentamicin. There are no reliable studies from which to derive a comparable value for trough (pre-dose) concentrations. The relative importance of peak and trough values for nephrotoxicity and ototoxicity is an unresolved subject of controversy. However, it seems possible that neither of these individual values, but rather the 'area under the time-concentration curve' is the major risk factor for toxicity. In view of the unpredictability of serum levels, especially in seriously ill patients in a fluctuating physiological state, periodical serum gentamicin assays should be performed. The main objective of these assays is to ensure that the peak serum levels attained are adequate, but not unnecessarily high.

Plasma levels of 5‐fluorouracil after oral and intravenous administration in cancer patients.

“…It is not clear which characteristics of the plasma concentration/time curve is most important in predicting toxicity. Peak and trough plasma levels and area under the concentration/time curve have all been suggested (Mawer, Ahmad & Dobbs, 1974;Barza & Lauermann, 1978). Similarly, it has been shown (Stolier, Hande, Jacobs, Rosenberg & Chabner, 1977) that monitoring of plasma levels after high dose methotrexate infusion can identify patients at high risk of toxicity.…”

Clinical Pharmacokinetics, Toxicity and Cost Effectiveness Analysis of Aminoglycosides and Aminoglycoside Dosing Services

“…Increasing trough concentrations may indicate accumulation of the drug, due to impaired renal function, calling for an alteration of dosage. In patients with major changes in renal function, extracellular fluid volumes and other basic pathophysiological parameters, assays should be performed more frequently, perhaps daily (30). It has been suggested that peak and trough concentration determinations in patients with normal renal function should be carried out 24 h after any change in aminoglycoside dosage, to ensure therapeutic concentrations (4).…”

Uptake of Gentamicin by Bullfrog Saccular Hair Cells in vitro

“…Gentamicin is used clinically to treat life-threatening, Gram-negative bacterial infections (e.g., meningitis), to prevent infection in patients with severe burns or large wound injuries, and also in premature babies. However, serious nephrotoxic and ototoxic side effects can occur when aminoglycosides are used clinically (Barza and Lauermann 1978;Lerner and Matz 1979).…”