A reversed-phase high-performance liquid chromatographic assay for the determination of the HIV protease inhibitors amprenavir (Agenerase®) and indinavir (Crixivan®) in human plasma is described, using a mobile phase consisting of 0.50 M phosphate buffer (adjusted to pH 5,5) - Milli-Q water - acetonitrile (120: 1,080: 800, v/v/v). A solid-phase extraction using C18 extraction columns (Discovery columns 100 mg, 1 ml Supelco) and a liquid-liquid extraction with 0.5 ml hydrogenocarbonate/carbonate buffer (adjusted to pH 10.6) and 6 ml methyl ter-butyl ether have been compared. The liquid-liquid extraction has been chosen to be easier and cheaper. The method has been validated over the range of 60 to 3,000 ng/ml for amprenavir and 20 to 3,000 ng/ml for indinavir using a 0.5 ml sample volume. The specificity, linearity, accuracy and precision have been studied. The limit of detection was respectively for amprenavir and indinavir 15 and 4 ng, and the limit of quantification was 60 and 20 ng/ml. Stability tests under various conditions were performed. This assay can readily be used in a hospital laboratory for the routine monitoring of plasma concentrations of amprenavir in HIV-infected patients. The trough plasma concentrations average has been determined in patients treated by amprenavir and indinavir for seven months.
Toxicological investigations are often required by clinicians in comatose patients with suspected poisoning. However, the usefulness of toxicological analyses to support a diagnosis of acute poisoning is debated among clinicians and the interpretation of laboratory tests is challenging given the wide diversity of analytical techniques available. We report the case of an 8-year-old boy who was admitted to an intensive care unit with severe respiratory depression and neurological impairment. In order to formulate appropriate hypothesizes about the diagnosis and circumstances of intoxication, clinicians consulted toxicologists for a comprehensive toxicological screening. Routine blood immunoassays were negative for common toxicants but urine tests were positive for opiates. A general unknown screening using liquid and gas chromatography combined with mass spectrometry detection confirmed the presence of morphine, codeine and related glucuronides metabolites in plasma and urine. Subsequently, morphine and codeine were quantified in plasma samples by online-SPE-LC-MS-MS. In addition, analyses performed with GC-MS and LC-MSn identified compounds used as markers when profiling illicit heroin, namely noscapine, dextromethorphan and codeine. In conjunction with the patient's history, clinical picture and circumstances of intoxication, toxicological findings strongly suggested an acute pediatric opioid overdose as a collateral damage of parental heroin abuse in the home. This case highlights the significant contribution of toxicological investigations in sensitive legal cases and the critical role of communications between clinicians and toxicologists.
A reversed-phase high-performance liquid chromatographic assay for the determination of the HIV protease inhibitors amprenavir (Agenerase) and indinavir (Crixivan) in human plasma is described, using a mobile phase consisting of 0.50 M phosphate buffer (adjusted to pH 5,5) - Milli-Q water - acetonitrile (120: 1,080: 800, v/v/v). A solid-phase extraction using C18 extraction columns (Discovery columns 100 mg, 1 ml Supelco) and a liquid-liquid extraction with 0.5 ml hydrogenocarbonate/carbonate buffer (adjusted to pH 10.6) and 6 ml methyl ter-butyl ether have been compared. The liquid-liquid extraction has been chosen to be easier and cheaper. The method has been validated over the range of 60 to 3,000 ng/ml for amprenavir and 20 to 3,000 ng/ml for indinavir using a 0.5 ml sample volume. The specificity, linearity, accuracy and precision have been studied. The limit of detection was respectively for amprenavir and indinavir 15 and 4 ng, and the limit of quantification was 60 and 20 ng/ml. Stability tests under various conditions were performed. This assay can readily be used in a hospital laboratory for the routine monitoring of plasma concentrations of amprenavir in HIV-infected patients. The trough plasma concentrations average has been determined in patients treated by amprenavir and indinavir for seven months.
β-Blockers are used as if they were equivalent. With ECG recordings in 42 patients we investigated the effect on sinus heart rate of four β-blockers given at three successive daily doses. Heart rate was dose-dependently decreased by all drugs except acebutolol, the effect of which decreased at a higher dosage. The maximal effects of metoprolol, nadolol, and propranolol were similar but the drugs differed in potency (dosage producing 50% of maximal effect, calculated from the dose-effect relationships; nadolol, 0.3 mg/ day; metoprolol, 120 mg/day; propranolol, 47 mg/day). Similar relationships were found with drug plasma concentrations (concentration producing 50% of maximal effect: nadolol, 3.5 ng/ml; metoprolol, 21 ng/ml; propranolol, 36 ng/ml) and with supine or upright heart rates and blood pressures. However, the drugs were not equivalent: In addition to its greater potency, nadolol differed from propranolol and metoprolol in the slope of its dose-response curve. We conclude that β-blockers can be compared by ECG recordings and that nadolol is different from the other β-blockers without intrinsic sympathomimetic activity. Clinical Pharmacology and Therapeutics (1986) 39, 361–368; doi:10.1038/clpt.1986.55
Chronic hypotension, infrequent though possible in chronic renal failure patients on hemodialysis, has harmful consequences on their physical state and hence general well-being. These patients often experience acute intradialytic manifestations while non-pharmacologic interventions as pharmacologic agents are sometimes insufficient to improve symptoms. Well tolerated, midodrine appears to be a suitable and effective agent as it raises blood pressure significantly via its effect on peripheral alpha-adrenergic receptors. The authors describe their use of midodrine in a dialysis patient for the longest period of time reported up to now, documented by a pharmacokinetic study, confirming long-term both clinical efficacy and safety of the drug.
Abstract Amphetamines, frequently used recreational drugs with high risk of toxicity, are commonly included in urine drug screens. This screening is based on enzyme immunoassay, which is a quick and easy-to-perform technique, but may lack specificity resulting from cross-reactivity with other compounds, causing false positive results. We present two cases of presumed false positive MULTIGENT® amphetamine/methamphetamine and MULTIGENT® ecstasy (Abbott®) immunoassays with the beta-blocker metoprolol. Both metoprolol-poisoned patients presented positive urine screening despite no history of drug abuse. No confirmation for amphetamine molecular structures was found with gas chromatography–mass spectrometry. The cross-reactivity was further investigated by doping urine samples with metoprolol and its two major phase-I metabolites. Metoprolol showed positive results for both amphetamine and MDMA tests at low concentrations (200 and 150 μg/mL, respectively). Metoprolol metabolites cross-reacted with the amphetamines immunoassay only, but at higher concentrations (i.e., 2000 μg/mL for α-hydroxymetoprolol and 750 μg/mL for O-demethylmetoprolol). In conclusion, false positive results in amphetamines and MDMA immunoassays are possible in the presence of metoprolol. Toxicologists should be aware of frequent analytical interferences with immunoassays and a detailed medication history should be taken into consideration for interpretation. In vitro investigation of suspected cross-reactivity should include not only the parent drug but also its related metabolites.
