Shortage of injectable diphenhydramine

The American Society of Health-System Pharmacists reports a shortage of injectable diphenhydramine hydrochloride. This drug is a first generation antihistamine. The injectable form is a useful addition to the initial treatment with epinephrine for a life-threatening allergic reaction to a bee sting, for example. Also, Parkinson's patients who are unable to take drugs by mouth may be given the injectable form to control the muscle tremors and stiffness caused by the disease.