Pharmacokinetic-pharmacodynamic modeling of mood and withdrawal symptoms in relation to plasma concentrations of methadone in patients undergoing methadone maintenance treatment.

The aims of the present study were to characterize the relationship between plasma racemic methadone and its enantiomers' concentrations with respect to their pharmacodynamic effects and to investigate the influence of potential covariates on the pharmacodynamic parameters in patients on methadone maintenance treatment (MMT). Eighty-eight regular subjects at the Sheffield Care Trust Substance Misuse Services were studied. Samples of blood and urine were collected before the daily dose of methadone.

Premorbid and current neuropsychological function in opiate abusers receiving treatment.

Background: There is an established corpus of evidence linking substance abuse with neuropsychological impairment, particularly implicating frontal lobe functions. These could potentially be premorbid to, rather than consequences of, direct effects of substance abuse.

Methods: A matched pairs design was employed in which currently abstinent opiate abusers in treatment were matched to 22 healthy control individuals.

Contribution of the activities of CYP3A, CYP2D6, CYP1A2 and other potential covariates to the disposition of methadone in patients undergoing methadone maintenance treatment.

Aims: To investigate the influence of different cytochrome P450 (CYP) activities and other potential covariates on the disposition of methadone in patients on methadone maintenance therapy (MMT).

Methods: Eighty-eight patients (58 male; 21-55 years; 84 White) on MMT were studied. CYP2D6 activity [3 h plasma metabolic ratio of dextromethorphan (DEX) to dextrorphan (DOR)] was determined in 44 patients (29 male; 24-55 years), CYP1A2 activity (salivary caffeine elimination half-life) in 44 patients (21 male; 24-55 years) and CYP3A activity (oral clearance of midazolam) in 49 patients (33 male; 23-55 years).

A six-year evaluation of methadone prescribing practices at a substance misuse treatment centre in the UK.

Objectives: To document changes in prescribing practice at a specialized substance misuse service in the UK occurring since the introduction of the 1999 UK National Guidelines on the management of drug misuse, and to explore a possible link between the length of time spent in methadone maintenance therapy (MMT) and the dosage prescribed.

Methods: A retrospective analysis of a computerized prescription database between 1996 and 2002 obtained from Sheffield Care Trust Substance Misuse Service was performed. The relationship between various measures of dosage and the length of time spent in MMT was investigated.

Can saliva replace plasma for the monitoring of methadone?

The aims of this study were to determine the relationship between saliva and plasma methadone concentrations and the influence of variability in saliva pH. Saliva and plasma samples were taken before the daily dose of methadone in 60 patients undergoing methadone maintenance treatment (MMT). Saliva pH was measured immediately after sampling, and concentrations of (RS)-, (R)-, and (S)-methadone in saliva and plasma were assayed by LC/MS.