Schnaper 1975, Study 2.

Methods	2‐week screening/observation period; 2‐week placebo period; inclusion criteria=supine DBP 95‐115 mm Hg; 6‐week double‐blind treatment period, followed by 1‐week placebo period, followed by 4‐week double‐blind continuation of fixed dosage of medication to responding patients Responding patients included: 1) those whose mean arterial pressure (DBP plus 1/3 PP), either supine or standing, had dropped by ≥15 mm Hg since end of preceding placebo period; and 2) patients whose supine or standing DBP decreased to ≤90 mm Hg. Patients who did not respond were dropped from study and were started on a titration regimen of 1 of 2 active drugs.
Participants	Prazosin 3 mg: n=20; baseline SBP/DBP not reported Placebo: n=10; baseline SBP/DBP not reported
Interventions	Prazosin 3 mg once daily Placebo
Outcomes	Change from baseline in trough standing SBP/DBP using mercury sphygmomanometer Change from baseline in trough standing SBP/DBP using mercury sphygmomanometer
Notes	BP change reported; SD of change not reported; endpoint BP and SD not reported; baseline BP and SD not reported; imputed overall trial mean SD of change for SBP and DBP; BP data from Table 4, p. 85
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not described.
Allocation concealment (selection bias)	Low risk	Quote: "...and each patient was given an individually coded bottle. A sealed envelope containing the code was attached to the bottle so the investigator could selectively break the code in an emergency."
Blinding (performance bias and detection bias) All outcomes	Low risk	Quote: "Medication was dispensed in identical capsules..."
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "In two patients, pressure rose to an unacceptable level after six weeks and four weeks, respectively. The code was broken, and they were given active therapy with prazosin. These patients are clearly failures on placebo and as such are significant to this trial. For this reason, they were included in the efficacy analysis as placebo patients, with the last pressures recorded during the double‐blind phase as their final values."
Selective reporting (reporting bias)	High risk	BP lowering efficacy was primary outcome. Safety/tolerability data not reported
Other bias	Unclear risk	Funding source not reported.