efavirenz + methadone + tizanidine

This is a combination of three medications: efavirenz (an antiretroviral medication used for HIV treatment), methadone (an opioid used for pain management and opioid dependence), and tizanidine (a muscle relaxant). When used together, significant drug interactions may occur. Efavirenz substantially reduces methadone plasma concentrations through induction of CYP3A4 and possibly CYP2B6 enzymes, which can precipitate opioid withdrawal symptoms in patients on methadone maintenance therapy. Tizanidine is a short-acting muscle relaxant that works as an alpha-2 adrenergic receptor agonist and may cause additional sedation when combined with methadone.