SPECIALIST PHARMACOLOGICAL & BIOCHEMICAL INTERVENTIONS

PLASMA TESTS

1. Alcohol.

Raised Mean Corpuscular Volume (MCV) in the absence of anaemia, and raised Gamma-Glutaryl- Transferase (GGT) are both indicative of although not specific for heavy use of alcohol in the medium-term (months/years). Carbohydrate-deficient transferase (CDT) is more highly specific for alcohol misuse and may be useful in distinguishing between raised liver enzymes associated with alcohol use and those caused by hepatitis C. Ethyl-glucuronide (EtG) is a metabolite of alcohol which is detectable in serum for up to 80 hours (Wurst et al, 1999), and may be useful in determining quite recent alcohol use when breathalyser readings are negative.

2. Methadone.

The future of monitoring of methadone compliance and dosage adjustment is likely to involve the use of computerised statistical models which predict trough plasma methadone levels for individuals.

Plasma methadone levels will need to be taken on two occasions from an individual client - after the first dose and again after one week of dosing. This will then be sufficient to design an individualised regime for the client. Random samples during treatment thereafter may be used to assess the effectiveness of therapy, methadone compliance, dosing habits and to rationalise detoxification regimes involving opiate antagonists, by comparing predicted with measured plasma levels (Wolff et al, 2000).

Currently, plasma methadone levels may play a part in monitoring compliance and in the tailoring of dosage to an individual's needs (there is a very large variation in plasma level achieved for a particular dose, between individuals). Trough levels taken immediately before the day's dose is due (as opposed to peak levels) should be used, and compared with previous trough methadone levels taken from the same individual. There are many factors that may result in changed plasma methadone levels apart from poor compliance (Eap et al, 1999), and methadone levels cannot be used as a 'stand-alone' measure of concordance.

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Alcohol Guidelines index

The above information is copyright of Dr Bruce Trathen MBBS MRCPsych (2006). ISBN 0-9545164-0-0. The author grants permission for these guidelines to be downloaded, copied and distributed freely, but does not grant permission for their sale.