The purpose of this study is to examine if chronic paracetamol dosing increases blood pressure in patients with known high blood pressure.

A prospective randomised, double-blind, crossover trial, comparing the effects of paracetamol 1g (500mg x2) four times daily with matched placebo on ambulatory and clinic BP, each given for 14 days, with a 14-day washout period.

Inclusion Criteria:

• ≥18 years old, men or post-menopausal women (women with no periods for 12 months or more, or those who have had a surgical menopause)
• Treated hypertensive patients with an average daytime ambulatory blood pressure measurement (ABPM) <150/95mmHg on stable doses of one or more antihypertensive medication (at least one of which should be; an ACE inhibitor, angiotensin receptor blocker or diuretic) for 3 months, or untreated hypertensive patients with an average daytime ABPM ≥135/85 but <150/95.

Exclusion Criteria:

• History of ischaemic heart disease, cardiac failure, cerebrovascular disease, liver impairment (ALT/AST>50IU/L) or stage 3-5 chronic kidney disease.
• History of overdose or suicidal ideation
• Patients weighing <55kgs.
• Patients with chronic pain requiring treatment, with a known allergy to paracetamol, or concomitant use of non-steroidal anti-inflammatories , oral anticoagulants or corticosteroids.