calfactant calfactant calfactant, also known as infasurf, is an intratracheal suspension derived from the natural surfactant in calf lungs. it is used in premature infants with lung surfactant deficiency that causes infant respiratory distress syndrome (irds). calfactantclinical datatrade namesinfasurfpregnancycategory n atc codenonelegal statuslegal status us: ℞-only identifierscas number183325-78-2 ychemspidernoneuniiq4k217vga9chemblchembl1201447 n ny (what is this?) (verify) mechanism of action lung surfactant is essential for effective ventilation as it modifies alveolar surface tension. irds is caused by a lung surfactant deficiency. calfactant serves as a substitute for the natural surfactant.