Cetirizine Reduces Gabapentin Plasma Concentrations and Effect: Role of Renal Drug Transporters for Organic Cations.

Gabapentin (GBP) is an organic cation mainly eliminated unchanged in urine, and active drug secretion has been suggested to contribute to its renal excretion. Our objective was to evaluate the potential drug-drug interaction between GBP and cetirizine (CTZ), an inhibitor of transporters for organic cations. An open-label, 2-period, crossover, nonrandomized clinical trial was conducted in patients with neuropathic pain to evaluate the effect of CTZ on GBP pharmacokinetics. Twelve participants were treated with a single dose of 300 mg GBP (treatment A) or with 20 mg/d of CTZ for 5 days and 300 mg GBP on the last day of CTZ treatment (treatment B). Blood sampling and pain intensity evaluation were performed up to 36 hours after GBP administration. The interaction of GBP and CTZ with transporters for organic cations was studied in human embryonic kidney (HEK) cells expressing the organic cation transporters (OCTs), multidrug and toxin extrusion proteins (MATEs), and OCTN1. CTZ treatment resulted in reduced area under the concentration-time curve and peak concentration compared with treatment A. In treatment B, the lower plasma concentrations of GBP resulted in reduced pain attenuation. GBP renal clearance was similar between treatments. GBP has low apparent affinity for OCT2 (concentration of an inhibitor where the response [or binding] is reduced by half [IC50 ] 237 µmol/L) and a high apparent affinity for hMATE1 (IC50 1.1 nmol/L), hMATE2-K (IC50 39 nmol/L), and hOCTN1 (IC50 2.1 nmol/L) in HEK cells. At therapeutic concentrations, CTZ interacts with hMATE1 and OCTN1. In summary, CTZ reduced the systemic exposure to GBP and its effect on neuropathic pain attenuation. However, CTZ × GBP interaction is not mediated by the renal transporters.

A fast and simple approach for the quantification of 40 illicit drugs, medicines, and pesticides in blood and urine samples by UHPLC-MS/MS.

A fast and simple approach to overcome challenges in emergency toxicological analysis, using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) has been developed, for the detection of analytes in blood and urine samples from the following drug classes: analgesics, benzodiazepines, antidepressants, anticonvulsants, drugs of abuse, and pesticides. These substances are relevant in the context of emergency toxicology in Brazil. The sample preparation procedure was relatively easy and fast to perform. The method was fully validated giving limits of in the range of 0.5 and 20 ng mL-1 for blood and urine samples. The intraday and interday precision and accuracy were considered adequate for all analytes once the relative standard deviation (RSD) (%) was lower than 20% for quality control (QC) low and lower than 15% for CQ medium and high. The developed method was successfully applied to 320 real samples collected at the Poison Control Center of São Paulo, and 89.1% have shown to be positive for some of the analytes. This confirms its applicability and importance to emergency toxicological analysis, and it could be very useful in both fields of clinical and forensic toxicology.

Identificaçäo cromatográfica de medicamentos freqüentemente administrados a atletas / Chromatographic identification of drugs usually adminestered to athletes

Reconhecidos os principais medicamentos administrados a jogadores de futebol, foram eles submetidos à técnicas analíticas usualmente empregadas no Controle Antidopagem com a finalidade de verificar possíveis interferências e, tornar mais rápida e segura a interpretaçäo dos resultados da análise