Table 3.
Summary of the 3 controlled trials for SCD-related priapism prevention
| Drugs and classes | Mechanisms of action | Trial phase | Eligibility | Sample size | Major findings | Limitations | Gaps |
|---|---|---|---|---|---|---|---|
| Sildenafil PDE-5 inhibitor |
cGMP inducer | Phase 2 A double-blind, placebo- controlled trial Follow-up duration: 8 weeks |
HbSS or HbSC 14-45 years Patients with SCD-related priapism who experience at least 2 attacks per week |
Estimated to have a sample of 48 participants, but only 13 participants were enrolled (randomized 1:1) | No difference in adverse effects 50% reduction of priapism episodes in the open-label extension A 4-fold decrease in major priapism episodes in the open-label extension |
Small sample size High risk of bias 5 of the 13 were lost to follow-up One got lost to follow-up out of the 8 who continued with the open-label phase Inconclusive evidence |
No child <18 years was enrolled The effect of the drug on acute priapism and sexual function was not assessed |
| Ephedrine and etilefrine α-Adrenergic agonists |
Increased sympathomimetic activity and penile smooth muscle tone | The trial phase is not specified Follow-up duration: 26 weeks |
HbSS/HbSβThal Age >12 years Regular clinic attendance for 6-month before recruitment |
Estimated to have a sample of 320, but only 131 were enrolled | No serious adverse effects | 86 enrolled in the screening phase, but only 46 completed the trial Poor compliance High risk of bias |
The effect of the drug on acute priapism and sexual function was not assessed |
| Stilbesterol Nonsteroidal estrogen |
Counters the androgen effect and possibly inhibits the testosterone-induced neuronal NO release | The trial phase is not specified Double-blind crossover, placebo-controlled trial Follow-up duration: 2 weeks |
Patients with SCD-related priapism who experience at least 2 attacks per week | The sample was not scientifically estimated 11 participants were enrolled, but only 9 completed the trial |
Priapism was controlled in most of the participants taking stilbesterol | Small sample size High risk of bias Washout period not described Protocol deviation (participants failed to take the drug) Recurrence within 2 weeks of stopping the drug |
Did not determine the drug effect on acute priapism Children were not included An optimal maintenance dose was not established |
HbSβThal, hemoglobin S β-thalassemia; HbSC, hemoglobin SC; HbSS, hemoglobin SS.