Alterations in methadone metabolism during late pregnancy.
Traditionally, methadone maintenance therapy has been a once-daily dosing schedule. The current study evaluates the effectiveness of this regimen during pregnancy. A total of 23 pregnant and 16 non-pregnant opioid-dependent patients were studied in two phases to evaluate pregnancy-dependent changes in methadone pharmacokinetics. In the first phase, pregnant patients had a statistically significant higher elimination rate constant (k) and lower half-life compared to non-pregnant controls. In the second phase, the apparent clearance (Cl/F) was significantly greater during pregnancy, with preliminary data suggesting that this observation results from a decrease in the fraction of dose absorbed (F). The implications of these findings on dosing regimens during pregnancy is discussed.
Jarvis
M A
MA
Department of Psychiatry, Medical College of Virginia Campus of Virginia Commonwealth University, Richmond 23298, USA.
Wu-Pong
S
S
Kniseley
J S
JS
Schnoll
S H
SH
D000328:Adult; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D006207:Half-Life; D006801:Humans; D008691:Methadone / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000627:therapeutic use; D009294:Narcotics / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000627:therapeutic use; D009293:Opioid-Related Disorders / Q000534:rehabilitation*; D011247:Pregnancy; D011248:Pregnancy Complications / Q000534:rehabilitation*; D011263:Pregnancy Trimester, Third / Q000502:physiology
D009294:Narcotics; D008691:Methadone