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Altered methadone pharmacokinetics in pregnancy: implications for dosing
R M Swift1, M Dudley, P DePetrillo
1Department of Psychiatry and Human Behavior, Brown University Program in Medicine, Providence, Rhode Island.
Journal of Substance Abuse
|January 1, 1989
Summary
Pregnant women on methadone maintenance therapy may experience lower drug levels. This study found a significantly shortened methadone half-life in an 8-month pregnant patient, suggesting altered dosing is needed during pregnancy.
Area of Science:
- Pharmacology
- Obstetrics
- Addiction Medicine
Background:
- Pregnant women undergoing methadone maintenance therapy (MMT) for heroin addiction often exhibit lower plasma methadone concentrations.
- This can lead to withdrawal symptoms and potentially impact treatment adherence.
Purpose of the Study:
- To investigate methadone pharmacokinetics in a pregnant patient with heroin addiction.
- To evaluate potential altered dosing strategies to maintain therapeutic methadone levels during pregnancy.
Main Methods:
- A single-subject pharmacokinetic analysis using a one-compartment model.
- Extended least-squares regression was employed to fit plasma concentration-time data.
- Simulations were performed to compare different methadone dosing regimens.
Main Results:
- The patient, 8 months pregnant with twins, exhibited a significantly reduced methadone half-life of 8.1 hours (compared to the typical >24 hours).
- Simulations indicated that twice-daily dosing of methadone (30 mg every 12 hours) achieved more sustained plasma concentrations than a 50% dose increase administered once daily.
- Twice-daily dosing is predicted to reduce withdrawal symptoms and improve treatment compliance.
Conclusions:
- Methadone pharmacokinetics are altered during pregnancy, necessitating adjusted dosing strategies.
- Twice-daily methadone administration appears more effective than increasing the daily dose for maintaining stable plasma levels in pregnant patients.
- Optimized methadone dosing regimens are crucial for managing withdrawal symptoms and enhancing treatment outcomes in pregnant women with opioid use disorder.