Closantel is a salicylanilide anthelmintic compound; exhibits different anthelmintic spectra and apparent toxicity in mammals.

Closantel inhibits drug resistant S. aureus and E. faecium with MICs of 1 μg/mL and 1 μg/mL. Closantel inhibits MRSA and E.faecalis with MICs of 2 μg/mL and 1 μg/mL. [1] Closantel completely blocks the infection of host cells with E. chaffeensis or A. phagocytophilum, treatment of infected cells 1 day post infection with closantel clears infection in dose-dependent manner. Closantel inhibits the autokinase activities of the three E. chaffeensis sensor kinases from E. chaffeensis. [2] Closantel (50 μg/mL) causes an initial burst of contractions of much greater amplitude and frequency than normal in tissue vessel, the stimulation of amplitude and frequency lasted for nearly 15 min and is accompanied by a rise in muscle tone, which reaches a maximum at 16 min, at a level greater than 1.5 times the maximal normal amplitude. [3]

Closantel (10 mg/kg) results in gross surface damage from 24 hours onwards in rats administrated with 25 metacercarial cysts of F. hepatica, in the form of erosion of the anterior and posterior extremities of the fluke and large-scale sloughing of the tegument on both dorsal and ventral surfaces. [3] Closantel (7.5 mg/kg) combined with broad-spectrum anthelmintic is very effective against H. contortus but ineffective against Trichostrongylus spp in lambs. [4] Closantel significantly reduces isotope levels in closantel-resistant adult Haemonchus contortus infected sheep. [5]