Diphenhydramine, which is more widely known in the United States as Benadryl, is a drug which is manufactured by McNeil-PPC, a subdivision of Johnson and Johnson. It is currently being marketed as an over-the-counter antihistamine, antiemetic, sedative, and hypnotic. It has also been used in the treatment of the extra pyramidal side effects of typical antipsychotics. Diphenhydramine was one of the first antihistamines ever invented. Dr. George Rieveschl invented it in 1942, and it became the first FDA approved antihistamine in 1946. The brand name Benadryl is currently trademarked by Pfizer, but many stores carry their own, cheaper version of the drug.
As an antihistamine Diphenhydramine has a recommended dosage of 25-50 mg Diphenhydramine every 6-8 hours, not to exceed 50-100 mg every 4-6 hours.Despite being a first generation over-the-counter antihistamine Diphenhydramine is still one of the most effective, and as a result still enjoys widespread use despite of its age. Diphenhydramine has been known to exhibit some sedative properties as well. Sometimes the product is used as a sleep aid, and is used an ingredient in other sleep aids, most notably Tylenol PM, where it is combined with acetaminophen, and several other pain relievers. Several generic store brands also contain Diphenhydramine as well. As a nonprescription sleep aid it is prepared as a hydrochloride salt and has a maximum dosage of 50mg in the US. Diphenhydramine has also seen limited use as a local anesthetic, mostly with patients who are allergic to other forms of locals, such as Lidocaine. There are also several topical formulas of Diphenhydramine available. They can come in many forms, including creams, lotions, and sprays. They are often used to relive itching, and have less of a chance of the user becoming drowsy, one of its more well known side effects.
Along with many of its first generation companions, Diphenhydramine has several side effects, and is a potent anticholingeric agent. This tends to cause extreme drowsiness to be a very common side effect among its users. There is also the possibility for motor-impairment, dry-mouth and throat, flushed skin, rapid or irregular heartbeat, blurred vision at near point owing to lack of accommodation, abnormal sensitivity to light, pupil dilation, urinary retention, constipation, difficulty concentrating, , short-term memory loss, visual disturbance, hallucinations, irritability, itchy skin, confusion, erectile dysfunction, and delirium. Some side effects, such as twitching may be delayed until the drowsiness begins to cease and the person is in a more “awake” mode. Severe prolonged twitching and muscle spasms have also been experience. The most common form of cardiac arrest associated with Diphenhydramine is caused by an over does, which can cause premature ventricular contraction. Diphenhydramine is similar to its cousin Dramamine, which only has 60% of the efficiency of Diphenhydramine. Some people have experienced allergic reactions to Diphenhydramine in the form of hives.
