Although precise estimates are not available, people who inject drugs appear to have a higher risk of TB infection and disease than the general population.195–198 This susceptibility is likely mediated by several factors, including co-morbid HIV infection, tobacco use and undernutrition, as well as increased risk of exposure related to homelessness and incarceration. The presentation of TB is not evidently altered by injection drug use itself, absent co-morbid, immune-altering conditions.
Injection drug use has been associated with reduced adherence to, and lower rates of, TB treatment completion.199 However, enhanced adherence supports such as provision of monetary or material treatment incentives, peer support, integration with opiate agonist therapy and DOT can improve adherence to TB treatment and monitoring.195,200,201 Several studies have highlighted that, with adequate adherence support, high treatment completion rates and good outcomes can be achieved in people who inject drugs.195,202,203
Co-morbid liver disease is common in people who inject drugs and screening for viral hepatitis and close treatment monitoring is prudent.195
Rifampin substantially reduces serum concentrations of methadone and buprenorphine, and this can precipitate opiate withdrawal syndrome.204 Furthermore, once rifampin is stopped, hepatic enzyme induction will wear off, usually over a period of about 2 weeks, and opiate serum concentrations can then increase, risking opiate toxicity. Rifabutin exerts less of an effect on the metabolism of these drugs and is not usually associated with withdrawal symptoms.205,206 Hydromorphone does not interact with the rifamycin drug class and dose adjustment is not necessary.
Given these clinically important drug-drug interactions, dosage adjustment of opioid agonist therapy and close monitoring is required throughout TB therapy. It is important that TB treatment providers alert opioid agonist providers prior to initiating rifamycin therapies and that an opiate monitoring strategy is in place. A notification to the opiate prescriber when the rifamycin is soon to stop is also strongly advised.
For patients who may not tolerate any change to opiate-agonist therapy, rifabutin can be substituted for rifampin in the TB treatment regimen.
Good practice statements
People with drug-use disorders should receive supportive care, including community-based directly observed therapy, to ensure optimal adherence, and should be linked to drug-use counseling and support services while undergoing TB therapy.
In patients receiving treatment for TB with rifamycin-based regimens who are also on opioid agonist therapy, it is important to adjust opioid agonist therapy in close collaboration with provider at both initiation and completion of the TB treatment course.
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