Background
Data of the Central Bureau of Statistic of Nepal from 2008 show a total of more than 46,000 illegal drug users, out of which 61% are injecting drug users (IDU). An injecting mix of medicines like opioids, benzodiazepines and antihistamines (the so-called South Asian cocktail) was prevalent. Furthermore, it is estimated that about 70,000 people are living with human immunodeficiency virus (HIV). The government of Nepal has started realizing and recognizing drug use and HIV as significant health and social issues. Harm reduction programs such as needle syringe exchange and opioid substitution treatment are being implemented.

Methods
The aim of this study is to obtain specific knowledge on the drug use behaviour and the health status of drug users with a focus on HIV in drug users with concurrent injection of opioids, benzodiazepines and antihistamines. After an initial mapping of Kathmandu Valley, 300 drug users in contact with different treatment and counselling centres were randomly chosen for the interviews. The research questionnaire was designed according to the European Addiction Severity Index (EuropASI) and Maudsley Addiction Profile standards.

Results
Ninety-one percent of the respondents are male and 9% female. Mean age is 28.7 years. Ninety-five percent are injecting drug users with a mean of 8.7 years of drug use history. Eighty-six percent are injecting different ‘cocktails’, usually made of buprenorphine, diazepam, promethazine and/or other substances (30-day prevalence). Similarly, 48% use heroin, whereas only 2% take cocaine/crack. Among those tested for HIV (N?=?223), 33% are positive (25% of the sample population). Compared to the other drug users (mainly heroin), the cocktail users show a higher HIV infection rate and more co-infections. Furthermore, risk behaviour, as e.g. needle sharing, is much more common among the cocktail users.

Conclusion
Currently, the mixture of medicines, opioids, benzodiazepines and antihistamines, is the predominant drug in Nepal; the pharmaceutical drugs needed to prepare the cocktail are less expensive than heroin and relatively easy to acquire. The cocktail users show a higher risk behaviour regarding the transmission of HIV than heroin drug users. It needs to be considered which HIV prevention measures are necessary to target the specific needs of drug users who inject a mixture of opioids, benzodiazepines and antihistamines, since the available services (such as needle syringe exchange) do not seem to cover their specific needs (high percentage of needle sharing).