Self-reports of consumption of amphetamines, cocaine and heroin in a survey among marginalized drug users.

Scientific literature offers few measurements of the quantities consumed by individual drug users. Such measurements are used for calculating the total drug consumption by the quantity-frequency method, and are extremely important for the comparison with waste water derived consumption estimates. The aim of this study was to measure quantities of amphetamines, cocaine and heroin consumed by marginalized drug users, using a multi-city questionnaire survey design. Variation by gender, age, frequency of use, main drug used and city was explored.The self-reported quantity used on the last day of use was for amphetamines on average 800mg, for cocaine 1014mg and for heroin 682mg. The self-reported usual dose was on average 297mg, 487mg and 297mg respectively, while the median value was 250mg for all three drugs. Overall, gender and age group were less important than frequency of use and the main drug used for establishing differences regarding the outcome variables. There were some differences regarding cities. No measure of purity was carried out at the interview sites, so the calculation of pure quantities was based on aggregate results from analyses of seizures by police and customs.The self-reported quantities of drugs consumed in three cities in Norway was equal to or somewhat higher among marginalized users than earlier assumed, where assumptions were based on limited literature and anecdotal information