A comparison of the cardiovascular effects of phenylpropanolamine and phenylephrine containing proprietary cold remedies.

1. The cardiovascular effects of the proprietary cold remedies, Mu-cron and Boots Cold Relief tablets were compared with 'placebo' Boots Pain Relief tablets in a double-blind study involving 16 healthy volunteers. Measurements (impedance cardiography, forearm plethysmography) were made over 4 h after oral drug administration. 2. Two Mu-cron tablets (containing phenylpropanolamine [(1R,2S)- plus (1S,2R)-norephedrine] 50 mg) increased blood pressure (maximal effect 18 +/- 1/8 +/- 1 mm Hg (mean +/- s.e. mean), P less than 0.001), stroke volume (4.9 +/- 0.8 ml m-2, P less than 0.05), total peripheral resistance (243 +/- 27 dyn s cm-5 m2, P less than 0.001) and forearm vascular resistance (1.3 +/- 0.3 mm Hg ml-1 min, P less than 0.01) and reduced the ratio of pre-ejection period to ventricular ejection time (-0.031 +/- 0.003, P less than 0.05) and forearm blood flow (-2.6 +/- 0.5 ml min-1, P less than 0.05) but did not affect heart rate or cardiac index. 3. Two Boots Cold Relief tablets (containing phenylephrine 10 mg and caffeine 60 mg) caused a small and short-lived increase in total peripheral resistance but did not have consistent effects on other measurements. Two Boots Pain Relief tablets (containing caffeine 60 mg) did not have important cardiovascular effects. 4. The cardiovascular effects of phenylpropanolamine, including vasoconstriction and an increase in cardiac performance, are consistent with its alpha- and beta 1-adrenoceptor agonist action. While it may help the symptoms of rhinitis, its use in patients with heart disease or hypertension is hazardous.(ABSTRACT TRUNCATED AT 250 WORDS)