Clinical pharmacology and therapeutics
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Clin. Pharmacol. Ther. · Aug 2011
Randomized Controlled TrialGenetic polymorphisms and the impact of a higher clopidogrel dose regimen on active metabolite exposure and antiplatelet response in healthy subjects.
A double-blind crossover study was conducted in four CYP2C19 genotype-defined metabolizer groups to assess whether increase in clopidogrel dosing can overcome reduced pharmacodynamic response in CYP2C19 poor metabolizers (PMs). Ten healthy subjects in each of four metabolizer groups were randomized to a clopidogrel regimen of a 300-mg loading dose (LD) and a 75-mg/day maintenance dose (MD) for 4 days followed by 600-mg LD and 150 mg/day MD, or vice versa. The exposure levels of clopidogrel's active metabolite H4 (clopi-H4) in PMs were 71% lower on the 75-mg/day regimen and 64% lower on the 150-mg/day regimen than the corresponding exposure levels in extensive metabolizers (EMs). ⋯ PMs who were on the clopidogrel regimen of 600-mg LD/150 mg/day MD showed clopi-H4 exposure and MPA levels similar to those in EMs who were on the regimen of 300-mg LD/75 mg/day MD. In a pooled analysis evaluating CYP1A2, CYP2B6, CYP2C9, CYP2C19, CYP3A5, CYP2D6, ABCB1, and P2RY12 polymorphisms (N = 396 healthy subjects), only CYP2C19 had a significant impact on antiplatelet response. In healthy CYP2C19 PMs, a clopidogrel regimen of 600-mg LD/150 mg/day MD largely overcomes diminished clopi-H4 exposure and antiplatelet response, as assessed by MPA levels.
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Clin. Pharmacol. Ther. · Aug 2011
Randomized Controlled TrialThe norepinephrine transporter inhibitor reboxetine reduces stimulant effects of MDMA ("ecstasy") in humans.
This study assessed the pharmacodynamic and pharmacokinetic effects of the interaction between the selective norepinephrine (NE) transporter inhibitor reboxetine and 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") in 16 healthy subjects. The study used a double-blind, placebo-controlled crossover design. ⋯ These effects were evident despite an increase in the concentrations of MDMA and its active metabolite 3,4-methylenedioxyamphetamine (MDA) in plasma. The results demonstrate that transporter-mediated NE release has a critical role in the cardiovascular and stimulant-like effects of MDMA in humans.
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Clin. Pharmacol. Ther. · Aug 2011
Prediction of torsade de pointes from the QT interval: analysis of a case series of amisulpride overdoses.
Electrocardiograms (ECGs) from a case series of 86 amisulpride overdose events in 66 patients were reviewed for abnormal QT intervals and torsade de pointes (TdP). Eight patients exhibited TdP. In this investigative case series, the magnitude of prolongation of the QT interval was a stronger predictor of TdP than the mere presence of a prolongation per se.
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In this issue, Hysek and colleagues present new data describing the impact of treatment with reboxetine on the effects produced by 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") in human volunteers. They demonstrate that several effects of MDMA are mediated by reboxetine's actions on norepinephrine (NE) transporters, an unexpected finding. Building on earlier work, their new data provide new insights into the pharmacodynamics of MDMA and other monoamine-releasing agents.