The additive and/or synergistic effects of combined sympathomimetic and methylxanthine therapy

Summary

Synergism between sympathomimetics and methylxanthines has been demonstrated in vitro. A series of 4 studies was carried out to investigate the synergistic effects of the two classes of drugs in vivo. The effects over α 2-hour period of inhaled isoprenaline and intravenous aminophylline were studied in 38 asthmatic patients. The results showed that when both drugs were given together there was a definite additive effect on the maximum expiratory flow and on the maximum mid-expiratory flow with a strong suggestion of synergism on the latter. Combining choline theophyllinate andsalmefamol, both given orally, resulted in an additive effect on peak expiratory flow rate in another group of 54 asthmatic patients but a synergistic effect on tremor of the hands. A further study in 14 patients receiving oral theophylline and inhaled salbutamol failed to demonstrate any additive effect when the two drugs were given together, and the results, so far, of an on-going study inpatients recovering from status asthmaticus have shown no interaction between inhaled rimiterol and oral theophylline. The clinical significance of the results is discussed.

Key Words::

• Theophylline
• adrenergic beta receptor agonists
• drug synergism
• asthma