Reversal of drug-induced priapism in a gelding by medication.

This research article describes a case where drug-induced priapism (abnormal, prolonged erection) in a gelding was successfully reversed using benztropine medication.

Introduction and Background

• Pearson and Weaver’s 1978 study on drug-induced priapism in yearling to 7-year-old colts and stallions forms the background of this article. The reported cases of paraesthesia were triggered by a tranquilizing drug known as acepromazine, typically used as a part of various anesthetic combinations. This resulted in penile engorgement and persistent firmness, akin to an erection in the horses.
• Out of the seven cases studied by Pearson and Weaver, five required penile amputation due to secondary complications like edema, fibrous stricture, and paralysis of the penis. Only two cases responded favourably to conservative treatment methods.

Case Study

• This study involves a 3-year-old thoroughbred gelding. On 31 October 1980, he was given 30 mg of acepromazine intravenously, which was a part of the anaesthesia administered prior to a routine hoof surgery. This led to priapism, as indicated by an unusual penile engorgement and turgidity.
• The erection-like state persisted throughout and beyond the surgical operation and the recovery phase. However, after the intravenous administration of 8 mg of benztropine, the priapism resolved within 30 minutes, with the penis returning to its normal, flaccid state inside the prepuce.

Discussion

• Phenothiazine derivative drugs like acepromazine are often used for their tranquilizing properties in horses, but one of the rare side effects they can induce is priapism.
• The authors point out that similar conditions have been reported in humans and cite references to this effect. For instance, Osborne in 1974 mentioned the successful reversal of human priapism using benztropine, an anticholinergic agent.
• Finally, the authors draw parallels between the priapism observed in the studied gelding and that in humans, noting similar characteristics of engorgement confined to the corpus cavernosum penis only, and not the glans penis.