(TRY-mix) Referring to three drugs that are mixed for injection into the penis to produce an erection and usually refers to a mixture of papaverine, phentolamine and prostaglandin E-1. May be spelled with a hyphen.

Combination therapy using a mixture of papaverine, phentolamine, and prostaglandin E1 (PGE1) has become popular as an intracavernosal treatment for erectile dysfunction owing to its high efficacy, lower incidence of pain, and lower cost per dose.

Combination therapy first was introduced in 1991 by Bennett and coworkers with a reported success rate of 92% in 116 Patients. A crossover study by McMahon comparing PGE1 alone with the 3-drug regimen in 228 patients also showed increased efficacy with the trimix for Patients with arterial insufficiency and mild-to-moderate venous insufficiency. Many clinicians reserve the trimix regimen for men with vascular erectile dysfunction who fail therapy with PGE1, the papaverine/phentolamine combination, or for Patients who experience severe penile pain with PGE1 injections. The lower dose of PGE1 used in the trimix often rectifies the pain component when compared with the higher PGE1 dose used in monotherapy.

A common trimix combination used by many Physicians is papaverine 0.5 mL (15 mg) + phentolamine 0.2 mL (0.5 mg) + PGE1 0.25 mL (10 mcg).