Sodium in soluble paracetamol may be linked to raised blood pressure

A 58 year old woman was diagnosed as having polymyalgia rheumatica in 2000. Her blood pressure was slightly raised (140/74 mm Hg). Her past medical history was otherwise unremarkable and her condition stable.

She takes 5 mg prednisolone a day, up to six over the counter Panadol tablets (GlaxoSmithKline, Brentwood; 500 mg paracetamol) a day, and Calcichew D3 Forte (Shire, Basingstoke; 1.25 g calcium carbonate and 10 μg colecalciferol) twice a day.

She complained of headaches, dizziness, and lethargy at a follow-up appointment in March 2004. She was hypertensive, with readings averaging 210/110 mm Hg. We advised her to see her general practitioner to recheck this.

Her blood pressure varied between 158/79 and 210/110 mm Hg over the next few days. Then she mentioned that eight weeks previously she had switched from Panadol tablets to soluble Panadol. Her lifestyle had apparently remained otherwise unchanged.

Each soluble Panadol contains 427 mg sodium. Her daily intake of sodium from six soluble tablets was 2.562 g, not including dietary sodium. The UK government recommends a daily intake of 2 g sodium (5 g salt) for women,1 and the World Health Organization recommends limiting sodium intake.2 Salt intake is linked to blood pressure.3 After returning to insoluble Panadol, her blood pressure was 145/85 mm Hg, confirmed by her general practitioner.

The increase in blood pressure seems temporally related to the switch in drug, which substantially increased in her sodium intake. This case shows the hypertensive effect that the high sodium content in a soluble paracetamol preparation may cause, particularly in susceptible patients. It also emphasises the importance of inquiring about over the counter drugs.

GlaxoSmithKline has no record of similar reports and felt it “unlikely that the sodium caused such a large increase in blood pressure,” given that restricting dietary sodium in normotensive and hypertensive populations produces modest reductions in blood pressure.4 The UK Committee on Safety of Medicines knows of no similar cases, but its database relates primarily to paracetamol's adverse effects and not non-drug ingredients.