Prophylactic efficacy and tolerance of low-dose intranasal interferon-alpha 2 in natural respiratory viral infections.

The prophylactic activity of intranasal human interferon-alpha 2 (HuIFN-alpha 2) was determined in a randomized, double-blind, placebo-controlled study. Healthy, working adults self-administered sprays of HuIFN-alpha 2(1.25 X 10(6) IU; n = 142) or placebo (n = 145) twice daily. Drug administration was stopped after 12 days because of the frequent occurrence of nasal irritation manifested by blood-tinged nasal mucus (44% HuIFN-alpha 2 versus 15% placebo, P less than 0.001) and associated nasal mucosal abnormalities. Over 80% of volunteers had participated in a similar field trial conducted 7 months earlier; no evidence of cumulative toxicity was detected. HuIFN-alpha 2 administration did not decrease the occurrence of illnesses associated with rhinorrhea, cough, or feverishness as compared to placebo, but the number of laboratory-documented respiratory viral infections was small (6 HuIFN-alpha 3 placebo). Intranasal HuIFN-alpha 2 1.25 X 10(6) IU twice daily was associated with significant local intolerance.