EFFECT OF HEAT-TREATMENT OF POTENTIALLY INFECTED BLOOD-SAMPLES ON THERAPEUTIC DRUG-MONITORING OF SELECTED DRUGS

OBJECTIVE: To investigate the effect of heat treatment on the outcome of drug analysis in whole blood and serum for eight drugs routinely assayed for therapeutic monitoring. DESIGN: All blood and serum samples (n=373) received at the pharmacy laboratory for therapeutic monitoring of carbamazepine, digoxin, gentamicin, kanamycin, phenobarbital, phenytoin, theophylline, and valproic acid were heated at 60-degrees-C for 30 minutes. Serum was subsequently assayed by fluorescence polarization immunoassay (TDx). SETTING: The study was conducted at the analytical laboratory of the pharmacy, using standard laboratory procedures. MAIN OUTCOME MEASURES: Analyses of heated samples were compared with analyses of untreated samples using a paired Wilcoxon signed-rank test. RESULTS: Serum concentrations of phenytoin from treated whole blood, and of gentamicin in treated serum, were significantly lower than in untreated samples. These differences, however, were small, clinically irrelevant, and lie within assay variation intervals. Heat treatment did not influence the outcome of analyses for carbamazepine, digoxin, kanamycin, phenobarbital, theophylline, and valproic acid. CONCLUSIONS: Heat treatment of whole blood and serum samples of the investigated drugs does not influence the outcome of drug analysis, although drug instability cannot be fully excluded. Heat treatment can protect laboratory technicians from HIV infection without influencing therapeutic monitoring of these drugs.