Tripelennamine interactions with the psychotomimetic sigma agonist N-allylnormetazocine

The pharmacological effects of individual and combined intravenous doses of the antihistamine tripelennamine and the psychotomimetic sigma benzomorphan opioid derivative, N-allylnormetazocine (NANM), on nociceptive reflexes, autonomic parameters and behavior were assessed in the chronic spinal dog. NANM (1.65 mg/kg, IV) produced antinociception, mydriasis, tachycardia, hyperthermia and behavioral signs of canine delirium. Tripelennamine (1.25 mg/kg, IV) produced antinociception, mydriasis and tachycardia without affecting behavior. The combined effects of the two drugs were additive except for heart rate. However, tripelennamine did not antagonize any of the physiological effects or the signs of canine delirium produced by NANM. The findings are inconsistent with the hypothesis that tripelennamine antagonizes the psychotomimetic NANM-like effects of pentazocine to make pentazocine-tripelennamine combinations (T's and Blues) more desirable as a heroin substitute.