Effect of clarithromycin on the pharmacokinetics and pharmacodynamics of pimozide in healthy poor and extensive metabolizers of cytochrome P450 2D6 (CYP2D6)

Zeruesenay Desta, Thomas Kerbusch, David A. Flockhart

Research output: Contribution to journalArticle

98 Citations (Scopus)

Abstract

Background: The use of pimozide is associated with prolongation of the QT interval and fatal ventricular arrhythmia. We recently reported 2 fatal cases in patients taking pimozide and clarithromycin and we have shown that clarithromycin inhibits CYP3A-mediated metabolism of pimozide in vitro. In this study, we examined the effect of clarithromycin on pimozide pharmacokinetics and QT interval changes in a total of 12 healthy subjects (7 men and 5 women), documented as extensive metabolizers or poor metabolizers of CYP2D6. Methods: In a randomized, double-blind placebo-controlled crossover design, subjects were given a single 6-mg oral dose of pimozide after 5 days of treatment with clarithromycin (500 mg twice a day) or a placebo pill. Blood samples were obtained before and for 96 hours after pimozide administration, and plasma pimozide and clarithromycin concentrations were measured by HPLC. Electrocardiograms for the analysis of the QTc intervals were recorded immediately before each blood sample. Results: Pimozide significantly lengthened QTc interval in the first 20 hours in both the placebo-treated groups (ΔQTc(max) = 13.3 ± 5.3 ms; P = .003) and clarithromycin-treated groups (ΔQTc(max) = 15.7 ± 9.5 ms; P = .005) compared with baseline values. This is consistent with an effect of the parent drug. Clarithromycin caused a significant increase in the peak plasma concentration (P = .015), terminal elimination half-life (P = .003), and area under the plasma concentration-time curve (P = .024) and a decrease in the clearance (P = .029) of pimozide. Mean QTC(max) observed within 20 hours of pimozide administration was significantly greater in the clarithromycin- treated group (23.8 ± 12.2 ms; P = .0397) than in the placebo-treated group (16.8 ± 6 ms). There was no significant effect of CYP2D6 or gender on the pharmacokinetics or pharmacodynamics of pimozide. Conclusions: A single 6-mg oral dose of pimozide resulted in measurable QT interval changes. Clarithromycin inhibited CYP3A-mediated pimozide metabolism and the resulting elevation in plasma concentrations may increase the risk of pimozide cardiotoxicity.

Original languageEnglish (US)
Pages (from-to)10-20
Number of pages11
JournalClinical Pharmacology and Therapeutics
Volume65
Issue number1
DOIs
StatePublished - 1999
Externally publishedYes

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Pimozide
Cytochrome P-450 CYP2D6
Clarithromycin
Pharmacokinetics
Placebos
Cytochrome P-450 CYP3A

ASJC Scopus subject areas

  • Pharmacology

Cite this

@article{caadc1a9001f450cb057d79f91419dbe,
title = "Effect of clarithromycin on the pharmacokinetics and pharmacodynamics of pimozide in healthy poor and extensive metabolizers of cytochrome P450 2D6 (CYP2D6)",
abstract = "Background: The use of pimozide is associated with prolongation of the QT interval and fatal ventricular arrhythmia. We recently reported 2 fatal cases in patients taking pimozide and clarithromycin and we have shown that clarithromycin inhibits CYP3A-mediated metabolism of pimozide in vitro. In this study, we examined the effect of clarithromycin on pimozide pharmacokinetics and QT interval changes in a total of 12 healthy subjects (7 men and 5 women), documented as extensive metabolizers or poor metabolizers of CYP2D6. Methods: In a randomized, double-blind placebo-controlled crossover design, subjects were given a single 6-mg oral dose of pimozide after 5 days of treatment with clarithromycin (500 mg twice a day) or a placebo pill. Blood samples were obtained before and for 96 hours after pimozide administration, and plasma pimozide and clarithromycin concentrations were measured by HPLC. Electrocardiograms for the analysis of the QTc intervals were recorded immediately before each blood sample. Results: Pimozide significantly lengthened QTc interval in the first 20 hours in both the placebo-treated groups (ΔQTc(max) = 13.3 ± 5.3 ms; P = .003) and clarithromycin-treated groups (ΔQTc(max) = 15.7 ± 9.5 ms; P = .005) compared with baseline values. This is consistent with an effect of the parent drug. Clarithromycin caused a significant increase in the peak plasma concentration (P = .015), terminal elimination half-life (P = .003), and area under the plasma concentration-time curve (P = .024) and a decrease in the clearance (P = .029) of pimozide. Mean QTC(max) observed within 20 hours of pimozide administration was significantly greater in the clarithromycin- treated group (23.8 ± 12.2 ms; P = .0397) than in the placebo-treated group (16.8 ± 6 ms). There was no significant effect of CYP2D6 or gender on the pharmacokinetics or pharmacodynamics of pimozide. Conclusions: A single 6-mg oral dose of pimozide resulted in measurable QT interval changes. Clarithromycin inhibited CYP3A-mediated pimozide metabolism and the resulting elevation in plasma concentrations may increase the risk of pimozide cardiotoxicity.",
author = "Zeruesenay Desta and Thomas Kerbusch and Flockhart, {David A.}",
year = "1999",
doi = "10.1016/S0009-9236(99)70117-7",
language = "English (US)",
volume = "65",
pages = "10--20",
journal = "Clinical Pharmacology and Therapeutics",
issn = "0009-9236",
publisher = "Nature Publishing Group",
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TY - JOUR

T1 - Effect of clarithromycin on the pharmacokinetics and pharmacodynamics of pimozide in healthy poor and extensive metabolizers of cytochrome P450 2D6 (CYP2D6)

AU - Desta, Zeruesenay

AU - Kerbusch, Thomas

AU - Flockhart, David A.

PY - 1999

Y1 - 1999

N2 - Background: The use of pimozide is associated with prolongation of the QT interval and fatal ventricular arrhythmia. We recently reported 2 fatal cases in patients taking pimozide and clarithromycin and we have shown that clarithromycin inhibits CYP3A-mediated metabolism of pimozide in vitro. In this study, we examined the effect of clarithromycin on pimozide pharmacokinetics and QT interval changes in a total of 12 healthy subjects (7 men and 5 women), documented as extensive metabolizers or poor metabolizers of CYP2D6. Methods: In a randomized, double-blind placebo-controlled crossover design, subjects were given a single 6-mg oral dose of pimozide after 5 days of treatment with clarithromycin (500 mg twice a day) or a placebo pill. Blood samples were obtained before and for 96 hours after pimozide administration, and plasma pimozide and clarithromycin concentrations were measured by HPLC. Electrocardiograms for the analysis of the QTc intervals were recorded immediately before each blood sample. Results: Pimozide significantly lengthened QTc interval in the first 20 hours in both the placebo-treated groups (ΔQTc(max) = 13.3 ± 5.3 ms; P = .003) and clarithromycin-treated groups (ΔQTc(max) = 15.7 ± 9.5 ms; P = .005) compared with baseline values. This is consistent with an effect of the parent drug. Clarithromycin caused a significant increase in the peak plasma concentration (P = .015), terminal elimination half-life (P = .003), and area under the plasma concentration-time curve (P = .024) and a decrease in the clearance (P = .029) of pimozide. Mean QTC(max) observed within 20 hours of pimozide administration was significantly greater in the clarithromycin- treated group (23.8 ± 12.2 ms; P = .0397) than in the placebo-treated group (16.8 ± 6 ms). There was no significant effect of CYP2D6 or gender on the pharmacokinetics or pharmacodynamics of pimozide. Conclusions: A single 6-mg oral dose of pimozide resulted in measurable QT interval changes. Clarithromycin inhibited CYP3A-mediated pimozide metabolism and the resulting elevation in plasma concentrations may increase the risk of pimozide cardiotoxicity.

AB - Background: The use of pimozide is associated with prolongation of the QT interval and fatal ventricular arrhythmia. We recently reported 2 fatal cases in patients taking pimozide and clarithromycin and we have shown that clarithromycin inhibits CYP3A-mediated metabolism of pimozide in vitro. In this study, we examined the effect of clarithromycin on pimozide pharmacokinetics and QT interval changes in a total of 12 healthy subjects (7 men and 5 women), documented as extensive metabolizers or poor metabolizers of CYP2D6. Methods: In a randomized, double-blind placebo-controlled crossover design, subjects were given a single 6-mg oral dose of pimozide after 5 days of treatment with clarithromycin (500 mg twice a day) or a placebo pill. Blood samples were obtained before and for 96 hours after pimozide administration, and plasma pimozide and clarithromycin concentrations were measured by HPLC. Electrocardiograms for the analysis of the QTc intervals were recorded immediately before each blood sample. Results: Pimozide significantly lengthened QTc interval in the first 20 hours in both the placebo-treated groups (ΔQTc(max) = 13.3 ± 5.3 ms; P = .003) and clarithromycin-treated groups (ΔQTc(max) = 15.7 ± 9.5 ms; P = .005) compared with baseline values. This is consistent with an effect of the parent drug. Clarithromycin caused a significant increase in the peak plasma concentration (P = .015), terminal elimination half-life (P = .003), and area under the plasma concentration-time curve (P = .024) and a decrease in the clearance (P = .029) of pimozide. Mean QTC(max) observed within 20 hours of pimozide administration was significantly greater in the clarithromycin- treated group (23.8 ± 12.2 ms; P = .0397) than in the placebo-treated group (16.8 ± 6 ms). There was no significant effect of CYP2D6 or gender on the pharmacokinetics or pharmacodynamics of pimozide. Conclusions: A single 6-mg oral dose of pimozide resulted in measurable QT interval changes. Clarithromycin inhibited CYP3A-mediated pimozide metabolism and the resulting elevation in plasma concentrations may increase the risk of pimozide cardiotoxicity.

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