Inosine pranobex (Isoprinosine®) is an immunomodulatory drug approved in several countries for the treatment of viral infections. This study compared the efficacy and safety of inosine pranobex versus placebo in subjects with clinically diagnosed influenza-like illness, including subjects with laboratory-confirmed acute respiratory viral infections. Subgroup analyses evaluated the efficacy of inosine pranobex compared to placebo in otherwise healthy (without related ongoing disease) subjects that were less than 50 years of age and healthy subjects that were at least 50 years of age. The effect of body mass index (BMI) was evaluated in subjects less than 50 years of age.

Inosine pranobex (BAN; also known as inosine acedoben dimepranol (INN) or methisoprinol) is an antiviral drug that is a combination of inosine and dimepranol acedoben (a salt of acetamidobenzoic acid and dimethylaminoisopropanol) in a ratio of 1 to 3. Inosine pranobex has no effect on viral particles itself.[citation needed] Instead, it acts as an immunostimulant, an analog of thymus hormones. It is most commonly used to treat the rare measles complication subacute sclerosing panencephalitis in conjunction with intrathecal interferon-alpha therapy.

In the UK, inosine pranobex is also indicated for mucocutaneous infections due to herpes simplex virus (type 1 and type 2) and for treatment of genital warts as adjunctive therapy to podophyllotoxin or carbon dioxide laser.