<prompt> Fastest acting anti-thyroid drug isSodium IodidePropyl thiouracilMethimazoleThiocyanate  <response>: Secretion inhibitors:These are fastest acting anti thyroid drugs. NaI KI Lugol iodine Thyroid peroxidase inhibitor CarbimazoleMethimazole Propylthiouracil Thiocyanate is NaIsympoer NIS inhibitor. Highly toxic Not used clinically 