12.6 Overlapping toxicities with anti-TB drugs and antiretrovirals

The main potential overlapping toxicities between anti-TB drugs and ARVs are:
– Hepatic reactions;
– Cutaneous reactions;
– Neuropathy;
– Nephrotoxicity.

The use of agents with shared adverse effect profiles should be avoided if possible. Often, however, the benefit of using drugs that have overlapping toxicities outweighs the risk. Thus, if two drugs with overlapping toxicities are essential in a regimen, increased monitoring for potential adverse effects is recommended rather than avoidance of a certain combination.

Important points:
– HIV patients are more likely to develop isoniazid-related peripheral neuropathy. Thus, all patients on isoniazid should receive pyridoxine PO (vitamin B6): 10 mg daily or 25 mg twice a week.
– The use of thioacetazone is contraindicated in HIV patients due to the high frequency of Stevens-Johnson syndrome and corresponding risk of mortality.
– Due to reports of increased renal toxicity during concurrent use of TDF and injectable agents (kanamycin, amikacin, and capreomycin), the use of TDF is not recommended during the intensive (i.e. injectable) phase of DR-TB treatment. If TDF is absolutely necessary, serum creatinine and creatinine clearance, and electrolytes should be monitored frequently.

For potential overlapping toxicities of antiretrovirals and anti-TB drugs, see Appendix 13.