INFORMATION FOR GENERAL PRACTITIONERS IN LOTHIAN No. 107 March 2007 Toxicology and treatment of drug users Role of toxicology • to confirm or exclude the consumption of heroin During assessment: Opiate metabolism - points to note • to identify drugs taken and corroborate history • Morphine may be derived from heroin or codeine • copy of results should accompany referrals for • ‘Heroin metabolites’ are derived only from heroin, so assessment indicate heroin use • medico-legally essential prior to starting substitute • Dihydrocodeine is metabolised to dihydromorphine, medication not to codeine or morphine During treatment: Positive and negative results: if a drug has been taken • as part of regular review: twice yearly on stable within the previous 48 hours, urine toxicology is almost patients, more often if there are concerns always positive. (A false negative may arise if urine is very • to confirm compliance and identify any non- dilute - lab. will usually indicate this). Most drugs clear prescribed drugs from the urine within 72 hours. Clearance rates of • more likely to encourage honesty if response is benzodiazepines vary: rohypnol will be cleared within 12 supportive rather than punitive hours, while diazepam can be detected for 7 days or more, • to inform discussion around goal setting and whether especially after chronic use. Cannabis may remain prescribed medication is adequate and appropriate detectable for 4 weeks or longer if used regularly. Urine toxicology A negative result may occasionally be reported at low doses Used in majority of cases. of methadone (less than 10-15 mg/day), in pregnancy or if Ask patient to provide fresh specimen of urine on the patient is a fast metaboliser of methadone. premises (not necessary to observe but check if warm - if If an unexpected positive or negative result is received, so, it is more likely to be theirs) contact laboratory as soon as possible - further tests Send 20mls in universal container (without preservative) may clarify the situation. to Biochemistry, Royal Infirmary. New regulations Responding to results require that samples are sent with absorbent material. Before testing, confirm patient’s contact details and current Request 'preliminary drug screen' and give drug history pharmacist: this makes it easier to respond to unexpected Oral swabs results. Consider arranging a short prescription and early Main advantage is that sample is patient specific. Can be review date. If a patient on prescribed methadone or purchased and contract arranged with testing lab dihydrocodeine shows evidence of illicit opiates, review is (currently private, non-NHS firms). Results in 3 – 7 days indicated. Prescribed dose may be too low. Interpreting results Early review is indicated if toxicology shows no evidence Preliminary drug screen: tests for amphetamines, of medication which is prescribed to a patient. including MDMA (Ecstasy), benzodiazepines, cocaine • Discuss with lab as above and obtain a repeat sample metabolites, methadone and opiates. Results available for testing as soon as possible on SCI Stores in 3-4days but will be up to 7 days if • Check with pharmacist if patient has been attending amphetamine confirmation is required. Buprenorphine regularly, especially if on supervised methadone. testing is available but takes up to 2 weeks. Testing for • If illicit drugs are present instead, try to establish if this Diconal, Ketamine or GHB is not available. RIE no has been an isolated lapse e.g. heroin use after missing longer tests for cannabinoids routinely, but will do so on regular pick-up at pharmacy, or more significant request. relapse. Identification of individual opiates: takes up to 2 weeks. • Full re-assessment and titration back onto treatment Either write 'opiate confirmation if positive' on initial with supervised consumption may be appropriate – or request or telephone the lab to request confirmation (on refer stored urine) after a positive opiate result is received. A detailed factsheet for users of the drugs of abuse Opiate confirmation is of particular value: screening service is circulated to all GPs and is available • when dihydrocodeine is prescribed - to confirm its from: presence • when the opiate screen is unexpectedly positive - it Toxicology Unit, Department of Biochemistry, Royal may show the opiate to be codeine from OTC Infirmary, Little France. Tel. 0131-242 7777 or medication email: [email protected]

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