Route of administration has a profound, but often overlooked, influence on the actual experience of the drug use itself, on the risk of resulting development of dependence, and on the nature of the harms to which drug users are exposing themselves. These three areas are reviewed. The influence of route of administration on drug effect is considered first with regard to overall effectiveness of absorption, and also with regard to speed of onset of effect. The implications for risk of dependence cover animal and human laboratory studies of reinforcement schedules, epidemiological studies, the attitudes of drug users themselves to the different routes of possible drug use and associated dependence risk and the postulated influences on progression to dependence. Finally, the relationship between route of drug use and health sequelae is explored for the three most widely used routes of administration of illicit drugs—snorting, smoking and injecting.

Route of drug use and its implications for drug effect, risk of dependence and health consequences.

Illicit drug control has been on the global agenda for more than a century. Infections have long been recognized as one of the most serious complications of drug abuse. Drug users are susceptible to pulmonary, endovascular, skin and soft tissue, bone and joint, and sexually transmitted infections caused by a wide range of bacterial, viral, fungal and protozoal pathogens. In addition, injection drug users are at increased risk for parenterally acquired infections such as human immunodeficiency virus, hepatitis B virus, hepatitis C virus, tetanus and malaria. Factors related to drug use, such as unsterile injection practices, contaminated drug paraphernalia and drug adulterants, increase the exposure to microbial pathogens. Illicit drugs also affect several components of the complex immune system and thus modulate host immunity. In addition, lifestyle practices such as multiple sexual partners, overcrowded housing arrangements and malnutrition serve as co-factors in increasing the risk of infection. In this review we present an overview of the unique aspects of microbial pathogenesis, immune modulation and common infections associated with drug use. We have restricted the definition of drug abuse to the use of illegal drugs (such as opiates, marijuana, cocaine, heroin and amphetamines), not including alcohol and nicotine.

Shooting up: the interface of microbial infections and drug abuse.

Polymerase chain reaction (PCR)-based assays targeting the small-subunit rRNA were developed and evaluated, allowing for the simultaneous diagnosis of Plasmodium falciparum and Plasmodium vivax DNA in human blood samples. The PCR methods and quantitative buffy coat (QBC) were compared in 402 patients. The heminested PCR method showed a sensitivity of 97.4%, which was superior to the sensitivity of the QBC method (91.7%, P < 0.05), to simple PCR (84.6%, P < 0.001), and to PCR with digoxigenin labeling (PCR-DIG) (88.5%, P < 0.001). The PCR-DIG and QBC analyses were more sensitive than simple PCR (P < 0.003 and P < 0.05, respectively). There was no significant difference between the sensitivities of the QBC assay and the PCR-DIG assay. The specificity for the 3 PCR-based methods was 100%, superior to the specificity calculated for the QBC assay (88.95%, P < 0.009). The frequency of a positive result in groups from endemic areas but without detectable parasitemia increased, in order, from simple PCR, QBC test, PCR-DIG, to heminested PCR. An association between a positive PCR result and a history of malaria was also found. Taken together, these data suggest that this technology could be further developed to screen people with oligoparasitemia and to monitor malaria treatment.

Development and optimization of polymerase chain reaction-based malaria diagnostic methods and their comparison with quantitative buffy coat assay.

We report the first outbreak of induced malaria among heroin users in Spain, and the first one caused by Plasmodium vivax in Europe. Five drug addicts from Madrid, who had never travelled to endemic areas, were admitted to hospital with fever and splenomegaly. Four had P. vivax malaria with low parasitaemia, ranging from 1 to 3% red blood cells. The fifth case was considered a "seropositive contact" because he had fever and positive malaria indirect fluorescent antibody test but negative blood smear. The source of infection was a young drug addict, who had often travelled to Equatorial Guinea. Another heroin user with a diagnosis of malaria refused to be admitted to our hospital for further study. All had shared contaminated injection equipment. Treatment with chloroquine was effective and none had recrudescence of malaria during a mean follow-up of six months. Drug addicts with unexplained fever may have been infected by malaria transmitted by sharing injections.

An outbreak of Plasmodium vivax malaria among heroin users in Spain

Em julho de 1990, foi registrado na cidade de Bauru, Estado de Sao Paulo, Brasil, um surto de malaria envolvendo usuarios de cocaina injetavel. Uma ampla investigacao epidemiologica, conduzida de 19 de julho a 13 de setembro, revelou que pelo menos 119 pessoas estavam envolvidas no surto, uma vez que haviam compartilhado seringas e agulhas com um ou mais casos confirmados nos 3 meses anteriores a ocorrencia. Cento e duas dessas pessoas foram localizadas e entrevistadas, e destas, 99 foram submetidas a exame de gota espessa e 91 a exames sorologicos para malaria. Foram confirmados por exame hemoscopico 21 casos de malaria por P. vivax, e 3 outros tiveram exame sorologico positivo para P. vivax. O controle da transmissao foi obtido fornecendo-se cloroquina aos envolvidos no surto, numa dose inicial de 10 comprimidos, seguida de doses supressivas semanais de 2 comprimidos ate que fosse identificado o ultimo comunicante. Amostras de soro coletadas na ocasiao revelaram, ao lado da malaria, uma alta prevalencia de infeccoes pelo HIV (58%) e pelo virus da hepatite B (40%). Foram discutidas as dificuldades para o controle do surto e a possibilidade da malaria vir a se tornar uma doenca endemica entre usuarios de drogas injetaveis, no Estado de Sao Paulo.

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Claude T. H. Friedmann

Papers

A malaria epidemic among heroin users.