Burnett 2014.

Methods	Double‐blind, placebo‐controlled parallel group trial followed by an open‐label extension for 8 weeks. Conducted prospectively from June 2008 to November 2012.
Participants	13 participants recruited from regional haematology and urology clinics randomised to sildenafil or placebo. Inclusion criteria were occurrences of at least two self‐reported priapism episodes per week and ability to provide written informed consent. Exclusion criteria were estimated GFR < 50 mL/min, clinical cirrhosis, pulmonary hypertension based on echocardiography, alcohol use exceeding 2 standard drinks daily, formal contraindications for using phosphodiesterase type 5 inhibitor therapy. Participant age: sildenafil (n = 6) mean (SD) age: 21.7 (5.3) years; placebo (n = 7) mean (SD) age: 23.0 (8.7) years. Disease status: SCD (confirmed SS or SC haemoglobinopathy) and recurrent ischaemic priapism. Hypertension no (%) placebo 1 (14.3%), sildenafil 2 (33.3%). Stroke no (%) placebo 3 (42.9%), sildenafil 1 (16.7%). Avascular necrosis no (%) placebo 1 (14.3%), sildenafil 0 (0). Acute chest syndrome no (%) placebo 1 (14.3%), sildenafil 2 (33.3%). Asthma no (%) placebo 2 (28.6%), sildenafil 2 (33.3%). Smoker no (%) placebo 1 (14.3%), sildenafil 2 (33.3%). Alcohol use no (%) placebo 3 (42.9%), sildenafil 3 (50%).
Interventions	Intervention: sildenafil 50 mg. Placebo: sugar pill. Either placebo or sildenafil was taken daily for 8 weeks. Participants were instructed to take the medication in the morning a few hours after awakening and without sexual stimulation. An 8‐week open‐label phase followed.
Outcomes	Primary efficacy outcome was 50% reduction in frequency in priapism episodes bi‐weekly from baseline at the end of the 8‐week double‐blind phase. Secondary outcomes included subjective improvements in episode frequency/duration and decrease in the number of of bi‐weekly episodes of priapism using a scoring system: 0 = no episodes; 1 = 1 to 2 episodes; 2 = 3 to 4 episodes; 3 = 5 to 8 episodes; 4 = 9 to 16 episodes; 5 = > 16 episodes. Adverse effects were also recorded for the whole trial period including the open‐label phase. Outcomes were measured via twice‐weekly nurse co‐ordinator phone calls to record progress, medication changes and adverse events. In‐clinic evaluations were carried out at baseline, week four and week eight which included repeat administration of trial instruments.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Participats were randomised in a 1:1 allocation. Method of randomisation not described.
Allocation concealment (selection bias)	Unclear risk	Allocation concealment not described.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Double‐blind trial where the participant, caregiver and investigator were blinded.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Double‐blind trial where the participant, caregiver and investigator were blinded.
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants were included in the analysis. Both ITT and per protocol analyses were carried out. No data were shown for decreased median weekly change in priapism episode score, just that there were no significant differences between groups. Adverse effects were not listed in the methods section but were reported in the results. Adverse events were reported for the whole trial period including the open‐label phase (confirmed by author team).
Selective reporting (reporting bias)	Unclear risk	The publication states that there were no significant differences between groups for decreased median weekly change in priapism episode score but no data were shown. The same paper reported adverse effects in the published paper but did not include this as an outcome in either the methods section or in the trial registration document.
Other bias	Low risk	None identified.