The prophylactic efficacy of isoprinosine was evaluated in a doubleblind fashion in volunteers challenged with two types of rhinovirus. In the rhinovirus 44 and 32 trials, each of 9 men received a placebo, and eight and 11 men received the drug, respectively. Oral isoprinosine, 6 g a day, was given for 2 days prior to intranasal challenge with 100 mean tissue culture infective doses of the virus and for 7 postchallenge days. In both trials the occurrence and severity of colds were greater in the placebo group, but the difference between the two groups was not significant. Higher antibody titers for both viruses and a greater number of rhinovirus 32 isolations were demonstrated in the drug group but without statistically significant differences. The prophylactic isoprinosine treatment may suppress the cold syndrome, but its effect was not convincingly apparent.Isoprinosine (NPT 10381, p-acetamidobenzoic acid salt of inosine-dimethylaminoisopropanol in a 1:3 [vol/vol]
403rhinovirus 44 was used as the challenge virus. This challenge virus was previously used in a drug evaluation clinical trial (8). The fourth WI-38 cell passage of rhinovirus 32 was prepared in this laboratory from the stock culture (SF 693 strain 2nd WI-38 cell passage, kindly supplied by Vincent V. Hamparian of the Ohio State University, Columbus). The examination of these challenge pools revealed no contaminants.Drug administration and viral challenge. Volunteers received orally either 1.5 g of isoprinosine at each meal and bedtime (6 g per day) or placebo tablets for 2 days prior to the intranasal inoculation of 100 TCID,5 of the challenge virus and for 7 consecutive postchallenge days. The drug and placebo tablets were supplied in coded bottles by Newport Pharmaceutical International, Inc., Newport Beach, Calif., and administered to volunteers in a double-blind fashion. A baseline observation period of 4 days was maintained to rule out incipient viral infection, and subsequently all subjects were kept in an isolation ward for 10 days after the challenge. Each subject was interviewed and examined by the physician once a day. Signs and symptoms of cold, i.e., rhinitis, rhinorrhea, nasal stuffiness, sore throat, pharyngitis, sneezing, cough, and others, were individually scored on a scale of 0 to 3+: 0, not present; 1+, mild; 2+, moderate; and 3+, severe. Each patient's chart was reviewed after discharge from the isolation ward, and the severity of induced rhinovirus illness of each subject was rated from 0 to 3+, according to the occurrence and severity of signs and symptoms and the duration of the illness. Hemogram, blood chemistries, including plasma and urine uric acid levels, and urinalysis were performed before, during, and after the isoprinosine treatment. The chest roentgenograms were done during the baseline period and before discharge from the ward.