The efficacy of 281.7 mg of
theophylline monohydrate and a combination of
theophylline (240 mg) +
hydroxyzine (7.5 mg) were compared in a double-blind, crossover, placebo-controlled study in 15 patients with chronic reversible
bronchial asthma. The patients took the drugs tested at 7.00 a.m., 3.00 p.m. and 10.00 p.m. During the 3-day trial period, the patients measured their peak expiratory flow (PEF) values every day at 7.00 a.m., 10.00 a.m. and 10.00 p.m., and during the last trial day,
theophylline serum levels were also determined. Use of
theophylline monohydrate resulted in slightly steadier serum
theophylline levels than with
theophylline +
hydroxyzine and morning levels of
theophylline were significantly higher (p less than 0.01) during the former treatment. Despite this, only the
theophylline +
hydroxyzine combination had a significant effect (p less than 0.05 at 7.00 a.m., p less than 0.01 at 10.00 a.m. and 10.00 p.m.) on PEF values at each time of measurement. There was a significant difference (p less than 0.05) in PEF values at 10.00 a.m. between the trial preparations in favour of the
theophylline +
hydroxyzine combination.
Theophylline +
hydroxyzine significantly decreased (p less than 0.05) nocturnal dyspnoea and most patients preferred this preparation. The differences in side effects were not statistically significant. The addition of
hydroxyzine to
theophylline increases the clinical efficacy of the latter.