p-Aminobenzoic acid (PABA) is a cyclic amino acid, belongs to the vitamin B group, and is used as a protective drug against solar insolation and in diagnostic tests for the state of the gastrointestinal tract in medicine. We were the first to establish that PABA is an inducer of endogenous interferon and immunomodulator and displays a virucidal, synergistic antiviral effect when combined with chemical drugs and the properties of a direct anticoagulant. Based on these properties, we elaborated a new medicinal drug "Actipol" which was introduced in clinical practice.