The Life Cycle of a Drug: Next Generation Product

Referring to the bar graph in the first of this series of posts, the next most profitable strategy manufacturers can use in the life cycle of a drug is to produce the next generation of a proven drug that is more effective and/or safer. The antihistamines (H1-antihistaminergic drugs) are a good example. The first generation provided relief from various allergic reactions leading to the release of histamine, but they also made people drowsy because of their effect on the brain. The second generation solved this problem because the chemical structure was modified so that they could not enter the brain. The transition from a second generation drug, terfenadine, to a third, fexofenadine occurred because researchers discovered that the human body changed terfenadine to fexofenadine. After that discovery, they gave people only fexofenadine and discovered that they were less likely to have heart rhythm problems.

In terms of the pharmaceutical industry, the patent for Benadryl (diphenhydramine) was held by Parke-Davis. This first generation drug is still popular because the sedating effect on the brain can help you sleep when your allergy symptoms are making you miserable. Hoechst Marion Roussel brought terfenadine to market under the brand name Seldane, and then bought the development rights for fexofenadine from Sepracor and sold it as Allegra.

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.