People who take heroin often drink heavily as well and in one study a third of patients attending a clinic for opiate use in the UK were identified as 'problem drinkers, hazardous drinkers or alcohol dependent.' Heavy drinking can worsen liver function in people already at risk of hepatitis C, can worsen treatment outcomes and can lessen the effectiveness of methadone sometimes playing a part in fatal overdoses. Researchers from University College and Trinity College (both in Dublin) looked at the prevalence of alcohol problems in people being treated in primary care (family doctors or GPs). From a sample of 196 patients 55% had hepatitis C. 35% were classified as being problem drinkers and these people were more likely to have attended a hospital emergency department in the last year. 14% of the sample could be classified as alcohol dependent.
Ryder, Niamh - Prevalence of problem alcohol use among patients attending primary care for methadone treatment BMC Family Practice 2009, 10(42)