​Diphen, which contains diphenhydramine, is an over-the-counter antihistamine commonly used to relieve allergy symptoms such as sneezing, runny nose, and itching. The cost of Diphen varies depending on the form and retailer. For instance, a 100-tablet bottle of diphenhydramine HCl 25 mg can be found for as low as $2.11 with a SingleCare coupon at participating pharmacies . Additionally, a 473 mL bottle of diphenhydramine elixir (12.5 mg/5 mL) is priced at $8.75 through the Mark Cuban Cost Plus Drug Company . These prices illustrate how shopping around and utilizing discount programs can lead to significant savings. To evaluate the cost-effectiveness of different purchasing options, it's helpful to comment calculer un pourcentage d'augmentation ou de diminution—that is, to calculate the percentage increase or decrease in prices between various sources.​