<prompt> Fastest acting antithyroid drugs ?Iodides of Na KPropylthiuracilMethimazoleNitrates  <response>: Ans. is a i.e., Iodides of Na Iodine and Iodides Iodine is the fastest acting thyroid inhibitor Most impoant action is inhibition of hormone release thyroid constipation; but all facets of thyroid synthesis may be affected. Excess iodide inhibits its own transpo in thyroid cells and may alter the redox potential of cells, thus interfering iodination - reduced T4T3 synthesis Wolff-chaikoff effect. 