THE PHARMACOLOGY OF PENICILLIC ACID

¹ Department of Pharmacology, Oxford

1. Penidillic acid is derived from Penicillium puberulum and other moulds. Its structure is known. A sample of crystalline penicillic acid has been examined pharmacologically.

2. It has a digitalis-like action on the heart of the frog, the rabbit auricle, the perfused cat's heart, and a very weak action in the heart-lung preparation of the dog. This activity suggests that it exerts its effect in the lactone form.

3. It has a dilator action on systemic blood vessels including the coronary vessels, and on the pulmonary vessels. When injected into the whole animal it often causes an initial rise of blood pressure probably due to stimulation of the vasomotor centre; the rise is absent in the spinal animal. This initial rise is followed by a prolonged fall.

4. It has an antidiuretic action which is detectable in rats after the subcutaneous injection of as little as one per cent of the L.D.50. This action can be seen on the isolated perfused kidney of the dog. This antidiuretic action may be due to a diminished permeability of the glomerular capillaries, since penicillic acid causes a diminished permeability of capillaries elsewhere.

(This work was done while the author was on leave of absence from the Department of Pharmacology, University College, Dublin.)