Orexin

OREXIN (Orexinum, phenyldihydroquinazoline, C₁₄H₁₂N₂). In medicine, orexin tannate (Orexinum tannicum), phenyldihydroquinazoline tannate, is used as a loose, light-yellow powder, odorless and almost tasteless; insoluble in water, sparingly soluble in alcohol and ether, easily soluble in weak (0.3%) hydrochloric acid; it is precipitated unchanged from solution by an excess of acid. Orexin was first investigated by Penzoldt, who proposed it as a stomachic for anorexia; animal experiments with a Pavlov-isolated stomach pouch confirmed the favorable effect of orexin on digestion. The action is caused by local irritation of the gastric mucosa, followed by hyperemia and enhancement of the function of the gastric glands. It is indicated in gastric diseases not accompanied by deep lesions of the organ, in anemia, chlorosis, the early stages of tuberculosis, in pediatric practice, for anorexia during convalescence, for intractable vomiting of pregnancy, and for seasickness. There are, however, indications both of doubtful benefit from orexin and of frequently manifested undesirable side effects of the drug (a feeling of heaviness in the epigastric region and burning). Dosage: 2 times a day an hour before meals, 0.3–0.1–1.0 g in cachets, in sugar water or milk for 5–10 days. For children, doses are reduced according to age. Iron preparations should not be prescribed simultaneously with orexin. Contraindications: hyperchlorhydria and gastric ulcer.—Orexinum basicum, phenyldihydroquinazoline, C₁₄H₁₂N₂, a white powder almost insoluble in water and alkalis, soluble in hydrochloric acid, alcohol, ether, and chloroform, with a bitter, burning taste. Locally on mucous membranes it acts as a caustic, and as a result, when administered orally, it produces pain in the mouth, a burning sensation in the stomach, nausea, and vomiting.—Orexinum hydrochloricum, orexin hydrochloride C₁₄H₁₂N₂HCl+2H₂O; a white crystalline powder of a very bitter, burning taste, soluble in 13–15 parts of water; upon storage in a desiccator, it loses its water of crystallization. The caustic side effect on mucous membranes is expressed even more sharply than in Orexinum basicum, which is why neither of the latter two preparations is used for medical purposes.