Cardiovascular effects of a chlorpheniramine/paracetamol combination in hypertensive patients who were sensitive to the pressor effect of pseudoephedrine

A systematic review of the effect of paracetamol on blood pressure in hypertensive and non-hypertensive subjects

AIM

To review current evidence on the effect of paracetamol on blood pressure (BP), the quality of the previous studies and the validity of the results, and to summarize these findings.

METHODS

A systematic literature review was performed by searching PubMed, the Cochrane library and EMBASE for publications between the years 1963 and 2012.

RESULTS

We identified three case reports, seven prospective observational trials, six randomized controlled trials, one commentary and two reviews. Some, but not all, of the observational studies, which included over 147 000 patients, showed an increased risk of hypertension with paracetamol use. The randomized studies were generally small and the results were inconsistent. Three studies, which included 104 patients, showed an increase of systolic BP by ~4 mmHg, two studies, which included 27 patients, reported no change in BP and one study, which included 21 patients, reported a fall in BP although no placebo arm was included for comparison.

CONCLUSIONS

The overall effect of paracetamol on BP is unclear. Given that paracetamol is often suggested as a safer alternative to non-steroidal anti-inflammatory drugs (NSAIDs), it would seem that further prospective evidence is now needed to address the effect of paracetamol on BP. This would be best done with larger studies in relevant cohorts using BP measured by ambulatory BP monitoring as the primary endpoint.

Differential responding of autonomic function to histamine H₁ antagonism in irritable bowel syndrome

BACKGROUND

The role of histamine in the pathophysiology of irritable bowel syndrome (IBS) is largely unknown. Dysfunction of the autonomic nervous system (ANS) in IBS patients is also not fully confirmed. We hypothesized that blockade of histamine H₁ receptors affects ANS responses differently between IBS subjects and controls.

METHODS

Subjects were 12 IBS subjects and 12 age- and sex-matched controls. Either 100 μg kg⁻¹ chlorphenamine or the same amount of saline was administered on different days. The rectum was stimulated with electrical currents of 0 mA (sham) or 30 mA. Autonomic nervous system function was measured using mean arterial pressure (MAP), heart rate (HR), high frequency (HF) component of HR variability, low frequency/high frequency ratio (LF/HF ratio) and plasma catecholamines and histamine. Subjective perceived stress during the examination was evaluated on an ordinate scale.

KEY RESULTS

Mean arterial pressure showed significant effects of diagnosis (P < 0.05) and drug × diagnosis interaction (P < 0.05). The MAP significantly increased after chlorphenamine administration in IBS subjects, but not in controls. Heart rate revealed a significant drug effect (P < 0.001), which decreased after chlorphenamine administration in controls, but not in IBS subjects. Perceived stress significantly increased by rectal stimulation (P < 0.001) and a significant stimulus × diagnosis interaction (P < 0.05) was revealed, indicating greater reduction in IBS subjects by chlorphenamine.

CONCLUSION & INFERENCES

Sympathetic vasomotor tone in IBS subjects differentially responded on administration of a histamine H₁ antagonist to that of controls. These findings suggest an increased histaminergic activity in IBS subjects.

Effects of repeated doses of pseudoephedrine on blood pressure and plasma catecholamines in normal subjects and in patients with phaeochromocytoma

1. Increases in blood pressure (BP) and in plasma noradrenaline concentration (NA) were observed after two doses of a non-prescription decongestant containing pseudoephedrine (PE) in two of three patients with phaeochromocytoma, before but not after removal of the tumour. The pressor response was terminated by oral phenoxybenzamine, and modified by prior exposure to this drug. 2. In eight normal subjects administration of the same two doses prevented falls in BP and in NA usually seen with prolonged recumbency, but neither BP nor NA increased. However, a pressor response was observed in a normal subject with a strong family history of hypertension. 3. Exposure to PE in non-prescription decongestants is not without risk in hypertension.