Effect of a mixture of pyridostigmine and atropine on forced expiratory volume (FEV1), and serum cholinesterase activity in normal subjects.

Pyridostigmine 0.143 mg kg-1 (maximum 10 mg) and atropine 0.0143 mg kg-1 (maximum 1 mg) were administered i.v. to six healthy male volunteers. Peripheral venous blood samples were drawn for measurement of serum cholinesterase activity. Maximum inhibition of the enzyme was found 5 min after injection with a decrease to 27 +/- 5% (mean +/- SEM) of the original activity. Forced expiratory volume in the first 1s (FEV1) was measured at fixed time intervals for 90 min. No decrease in FEV1 was observed; on the contrary, there was a small increase. We conclude that atropine effectively antagonizes the muscarinic side-effects of pyridostigmine on bronchial smooth muscle tone and bronchial secretions, when administered in clinical doses to normal human subjects.