Infectious disease comorbidities adversely affecting substance users with HIV: hepatitis C and tuberculosis.

The linkage between drug use, particularly injection drug use, and HIV/AIDS, hepatitis C (HCV), and tuberculosis (TB) has been recognized since the beginning of the HIV pandemic. These comorbid conditions affect drug users worldwide and act synergistically, with resultant adverse biologic, epidemiologic, and clinical consequences. Prevention, care, and treatment of TB and HCV can be successful, and both diseases can be cured. Special clinical challenges among drug users, however, can result in increased morbidity, mortality, and decreased therapeutic success. Among these are limited disease screening, inadequate and insensitive diagnostics, difficult treatment regimens with varying toxicities, and complicated pharmacokinetic and pharmacodynamic drug interactions. These may result in delayed diagnosis, deferred treatment initiation, and low completion rates, with the potential for generation and transmission of drug resistant organisms. Strategies to address these challenges include outreach programs to engage substance abusers in nonmedical settings, such as prisons and the streets, active screening programs for HIV, HCV, and TB, increased and broadened clinician expertise, knowledge and avoidance of drug interactions, attention to infection control, use of isoniazid preventive therapy, and creative strategies to insure medication adherence. All of these require structural changes directed at comprehensive prevention and treatment programs and increased collaboration and integration of needed services for substance abusers.