Plasma concentrations of propranolol and 4‐hydroxypropranolol during chronic oral propranolol therapy.

1 The plasma levels of propranolol and 4‐hydroxypropranolol have been measured in 17 hypertensive patients receiving chronic oral therapy with propranolol. 2 The range of plasma propranolol concentrations was from 5.3 to 300 ng/ml, and that of 4‐hydroxypropranolol was from 2.1 to 36.0 ng/ml. 3 The mean (+/‐ s.d.) plasma concentration ratio of 4‐ hydroxypropranolol to propranolol was 0.130 (+/‐ 0.005); however, a very wide range was observed with individual values ranging from 0.057 to 0.241. 4 A statistically significant correlation was observed between the plasma concentration of 4‐hydroxypropranolol and that of propranolol. 5 Propranolol and 4‐hydroxypropranolol plasma concentrations were each significantly, but poorly, correlated with daily propranolol dose. 6 The clinical significance of the results has been discussed. 1979 The British Pharmacological Society