Protective effect of drugs on histamine-induced asthma.

Controlled standardised histamine inhalation tests were carried out in 21 asthmatics to determine the degree of non-specific bronchial hyperreactivity with and without prior treatment with several anti-asthmatic drugs. A significant protective effect was produced by inhaled salbutamol, 200 microgram, ingested salbutamol, 4 mg, inhaled Sch1000, 40 microgram inhaled atropine sulphate, 290 microgram, and ingested choline theophylinate (200 or 400 mg) producing serum theophylline levels over 10 mg/l. Inhaled salbutamol was consistently the most effective and was significantly better than the other drugs. The protective effect between the other four was not significantly different. Drug side-effects occurred only with the ingested drugs. No significant protection was detected after ingested choline theophyllinate producing serum theophylline levels of less than 10 mg/l, inhaled sodium cromoglycate, 20 mg given once or six-hourly for one week, or ingested ascorbic acid, 1 gram.