Singh 2006.

Methods	Randomised, double‐blind, placebo‐controlled cross‐over trial 6 weeks duration with a wash‐out of 2 weeks
Participants	Inclusion criteria: People with severe PAH, 10 each of IPAH and Eisenmenger syndrome. Exclusion criteria: People with coronary artery disease Significant hepatic and renal dysfunction Those with contraindication to sildenafil therapy Cases of PH as a result of other causes were excluded from the study (WHO Group 1) WHO FC II/III n = 20
Interventions	Oral sildenafil versus placebo Adult participants were given 25 mg sildenafil on the first day and repeated after 6 hours under observation. If there was no hypotension, they were given 100 mg 3 times a day. In children weighing < 30 kg, an initial dose of 3.125 mg of sildenafil was given and maintained at 25 mg 3 times daily. In older children weighing > 30 kg, initial dose of 6.25 mg was given and maintained at 50 mg 3 times a day. Participants were given second dose only if there was no significant fall in BP. Treatment was given for 6 weeks, which was followed by a 2‐week washout before crossing over Routine medication, as prescribed by the treating physician, including digitalis, diuretics, and oral anticoagulants, was continued throughout the study Compliance was assessed by the pill‐count method
Outcomes	The primary endpoint of efficacy was the improvement in distance covered in 6MWD. Secondary endpoints were reduction in PAP as measured by Doppler echocardiography after 6 weeks of treatment, improvement in clinical condition, NYHA class, and exercise duration and metabolic equivalents (Mets) achieved on modified Bruce exercise protocol
Notes	Funding source not stated Location and dates of enrolment not stated
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation, blinding, and drug/placebo administration were done by the Department of Pharmacology
Allocation concealment (selection bias)	Low risk	Placebo‐controlled
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Placebo‐controlled
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Unclear if outcome assessors were blinded
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	It is not explicitly stated if there were any withdrawals
Selective reporting (reporting bias)	Low risk	Prespecified outcomes were reported
Other bias	Low risk	Other risk of bias is unlikely