This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:

Primary objectives

To assess the dose‐related effect of clonidine as compared to placebo in patients with primary hypertension as well as in patients without primary hypertension (postmenopausal women with hot flashes; patients treated for opioid withdrawal; and patients treated for alcohol addiction) on:

1. Systolic blood pressure

2. Diastolic blood pressure

3. Withdrawals due to adverse effects

Secondary objectives

1. Heart rate

2. Pulse pressure

3. Blood pressure variability