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Aims To assess the dose–effect relationship between self-reported drug intake and the concentration of drugs and/or their metabolites in hair and to examine factors that may mediate this relationship. Design and setting A cohort study among young drug users (YDU) in Amsterdam, the Netherlands, which began in July 2000. At intake, YDU were asked to report their average drug intake over a 2-month period. A hair sample was taken and then analysed for cocaine, benzoylecgonine (BE), morphine, 6-monoacetylmorphine and methadone. Weighted least-squares regression analysis was used to model hair-test results as a function of reported drug use. Participants Subjects were 95 YDU (using cocaine, heroin, methadone and/or amphetamines at least 3 days/week) aged 18–30 residing in Amsterdam in 2000–2001. Findings Of the 95 YDU, one-third were women; mean age was almost 26; 30% had black hair, 33% blond hair and 37% brown hair. Cocaine use was reported by 92%, heroin by 75% and methadone by 64% of participants. All hair samples contained one or more drugs. Crude correlation coefficients between reported drug doses and drug concentrations in hair ranged between 0.45 and 0.59. The multivariate regression analysis showed that, for one or more types of drug, black-haired people, women and non-western European people had relatively high drug concentrations in hair (significant slope effects). The corresponding multivariate correlation coefficients ranged between 0.63 and 0.87. Conclusions Hair testing can be used to quantify drug use in epidemiological studies, given that factors such as hair colour and sex are taken into account.

Aims. To give a detailed description of injection-related risk behaviours, and to estimate the relative importance of these behaviours with regard to HIV transmission. Design. The present study was part of the Amsterdam Cohort Study of drug users. Setting. In Amsterdam, a city with extensive preventive measures, large HIV-risk reductions have taken place, but no further decreases have occurred since 1991. Participants and measurements. A detailed questionnaire on injecting risk behaviour was completed by a cross-section of participants in 1992/93 (n = 168). Among 48 HIV-seroconverters, a questionnaire was completed concerning possible HIV-transmission route. Findings. Of 96 HIV-negative participants, 23% deliberately borrowed a used syringe, 18% reported possible "accidental" borrowing, 9% front/backloading, 4% simultaneous injection, and 32% possible sharing of ancillary equipment. Of deliberate borrowers, 64% borrowed from a person with unknown or positive HIV serostatus, and 81% did not appropriately clean the equipment; 79% borrowed in the absence of serious withdrawal symptoms. Risk factors differed for deliberate and 'accidental' borrowing. Among the HIV seroconverters, the most likely transmission route was borrowing in 29% of cases, front/backloading in 8%, borrowing or front/backloading in 21%, unprotected sexual contact in 23% (mainly with regular partner) and either injecting or sexual risk in 13%. Women were much more likely to report sexual transmission ( p = 0.016). Borrowing was admitted by 43% before, and 64% after awareness of HIV-seroconverion. Conclusions. As the injecting risk is high, usually deliberate, and often in the absence of withdrawal symptoms, further prevention seems difficult. Although deliberate borrowing is the main risk for HIV seroconversion, unprotected sexual contacts and front- and backloading may be more important than previously thought in Amsterdam. Under-reporting of borrowing is probably substantial, but does not alter the above conclusions.

Objectifs: caracteriser les Centres de Distribution de Methadone d'Amsterdam en identifiant les determinants du dosage de la methadone et les caracteristiques des clients dans les differents types de programmes de methadone. Projet et participants: 444 participants d'une etude sur un groupe d'usagers de drogue d'Amsterdam qui avaient accepte de mettre en relation les donnees du Registre Central de Methadone aux donnees du groupe. Resultats: de 1985 a 1994, le dosage de la methadone a augmente de 41 a 59mg/jour. La dose moyenne de methadone etait plus elevee en Europe de l'ouest, chez les allemands, les usagers de drogue plus âges, seropositifs, et qui se prostituaient depuis plus longtemps, chez les usagers habituels de drogue par injection, chez ceux ayant plus d'anciennete en ce qui concerne les injections et l'usage de methadone, ainsi qu'une frequence plus elevee de traitements a la methadone, et chez les clients du Service de soins ambulatoires pour etrangers et prostitues. Pour les clients de medecine generale, dans les services de police et dans les prisons, la dose de methadone etait plus faible. Les auteurs ont observe differentes categories de caracteristiques des clients chez ceux qui recevaient la methadone dans un poste ou dans un bus de distribution de methadone, dans le service ambulatoire pour etrangers et prostitues, en medecine generale et dans les services de soins a domicile pour toxicomanes. Conclusions: ces resultats indiquent que le systeme d'Amsterdam est hautement differencie en ce sens ou il est largement concordant avec la politique generale voulue pour le traitement a la methadone.