Effects of altitude and two decongestant-antihistamine preparations on physiological functions and performance.

Fourteen men were studied to determine the combined effects of two altitudes--388 and 3,810 m or 1,274 and 12,500 ft--and three preparations--lactose placebo, Compound A (Actified, and Compound B (Dristan). Subjects reported least attentiveness with A and greatest with placebo. Fatigue increased significantly with time while energy, interest, and attentiveness decreased. The Multiple Task Performance Battery (MTPB) showed no effects of altitude, drugs, or time on overall performance; however, performance declined with time in several tasks, while problem solving improved. Subjects enjoyed the problem-solving tasks and may have given them preference as levels of interest declined. Though the MTPB overall composite scores did not change significantly, physiological parameters and subjective evaluations indicate that type of compound and time after ingestion are important. Declines in energy and attentiveness 2.5 h after ingestion could result in neglect of important--although routine--tasks. Hypoxia might enhance this effect and consequences might be worse in subjects whose medical conditions require these drugs.