A small descriptive cohort study reported that patients who are both CYP2B6 slow metabolisers and NAT2 slow acetylators are at increased risk of severe neurotoxicity when isoniazid and efavirenz are co-administered.14 Prospective data on the risk of neurotoxicity, hepatotoxicity, dyslipidaemia, and dysglycaemia associated with this pharmacokinetic and pharmacogenetic interaction are limited. The gene discussed is CYP2B6; the disease is inherited lipid metabolism disorder.