Short-term effects of β-adrenoceptor blocking drugs with and without cardioselectivity and intrinsic sympathomimetic activity on lipoprotein metabolism in hypertriglyceridaemic patients and in normal men

1. In six patients with hypertriglyceridaemia presenting whilst receiving treatment with β-adrenoreceptor blocking drugs (mean serum triglycerides 31.2 mmol/l) the half-life (t_1/2) of an intravenously administered triglyceride emulsion was 32.8 ± 7.9 min (mean ± sem) on β-blocker and 22.8 ± 4.8 min after stopping β-blocker treatment.

2. In three of these patients subsequent administration of a β-blocker with intrinsic sympathomimetic activity had no effect on t_1/2.

3. In a cross-over trial of placebo, atenolol (β₁-blocker), propranolol (β₁- and β₂-blocker) and pindolol (β₁- and β₂-blocker with intrinsic sympathomimetic activity) in 11 normal men t_1/2 was 11.8±0.9, 12.6±1.1, 14.3±1.7 and 12.4±1.1 min respectively. None of the apparent differences achieved statistical significance, but in two men marked increases in t_1/2 occurred on propranolol.

4. The concentrations of serum triglycerides and very low density lipoprotein cholesterol in the normal men were, however, increased by β-blockade, most markedly by pindolol.

5. Serum high density lipoprotein (HDL) cholesterol concentration decreased in normal men on β-blockers, most clearly on atenolol and propranolol. This decrease was due to a reduction in cholesterol in the HDL₂ subfraction.

6. No statistically significant effects on serum low density lipoprotein cholesterol or apolipoprotein B concentrations occurred in the normal men.

7. The doses of atenolol and propranolol used in this study were equipotent as judged by the heart rate response to exercise.