Johnson 1990.

Methods	Single‐centre study Randomization: "In a cross‐over design study, patients were randomly assigned to receive either methyldopa...for three weeks followed by matching placebo tablets for three more weeks, or the reverse sequence of treatments." Blinding: not reported Withdrawals: not reported Lost to follow‐up: not reported Treatment duration: patients took both methyldopa and placebo each for three weeks Analysis type: not reported
Participants	Geographic region: Study setting: not reported N=16 Age range: 26‐67 Gender: 5 males, 11 females Race: not reported Blood pressure at entry: not reported Co‐morbid conditions: not reported Inclusion criteria: essential hypertension; untreated supine diastolic blood pressure 90‐105 mm Hg Exclusion criteria: not reported
Interventions	All anti‐hypertensives and any other drugs were discontinued for a four week washout period before trial entry Methyldopa 250 mg three times daily x 3 weeks (N=16) Placebo three times daily x 3 weeks (N=16) ***Cross over trial: All 16 patients rotated throughout the above treatment arms without washout periods between treatment arms
Outcomes	Supine blood pressure Standing blood pressure
Notes	Assessment of medication compliance: not reported Final number of patients included in each arm when reporting results: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	Unclear risk	Unclear
Allocation concealment?	Unclear risk	Unclear
Blinding? All outcomes	High risk	Open label
Incomplete outcome data addressed? All outcomes	Unclear risk	Unclear ‐ final number of patients in each treatment arm was not reported in results
Free of selective reporting?	High risk	Did not report data for supine blood pressures