|
Diphenhydramine (; abbreviated DPH, sometimes DHM) is a first-generation antihistamine possessing anticholinergic, antitussive, antiemetic, and sedative properties that is mainly used to treat allergies. It is also used in the management of drug-induced parkinsonism and other extrapyramidal symptoms. The drug has a strong hypnotic effect and is FDA-approved as a nonprescription sleep aid, especially in the form of diphenhydramine citrate. It is produced and marketed under the trade name Benadryl by McNeil Consumer Healthcare in the U.S., Canada, and South Africa (trade names in other countries include Dimedrol, Daedalon, and Nytol). It is also available as a generic or store brand medication. Diphenhydramine was one of the first antihistamines developed in the late 1940s and is the prototype of the ethanolamine class of first-generation antihistamines, which also includes orphenadrine, phenyltoloxamine, doxylamine, and halogenated diphenhydramine derivatives. It was first synthesized by George Rieveschl and first made publicly available through prescription in 1946.〔(Ohio History central: Benadryl ); accessed Jan. 5, 2011〕 == Medical uses == Diphenhydramine is a first-generation antihistamine used to treat a number of conditions including allergic symptoms and itchiness, the common cold, insomnia, motion sickness, and extrapyramidal symptoms.〔(【引用サイトリンク】 Diphenhydramine Hydrochloride Monograph )〕 Diphenhydramine has been found to have a higher efficacy in treatment of allergies than some second-generation antihistamines (such as desloratadine) but a similar efficacy with others (such as cetirizine). It is frequently used when an allergic reaction requires fast, effective reversal of a massive histamine release. Diphenhydramine is available as an over-the-counter drug or prescription-only solution for injection. Injectable diphenhydramine can be used for life-threatening reactions (anaphylaxis) to allergens such as bee stings, peanuts, or latex, as an adjunct to epinephrine. As a potent antagonist to acetylcholine in muscarinic receptors, diphenhydramine is used to treat Parkinson's disease-like extrapyramidal symptoms caused by antipsychotics. The muscarinic receptor antagonism leads to correction of levels of dopamine, the neurotransmitter responsible for control of motor function in the brain, similar to the effect of other antimuscarinic agents such as atropine. Diphenhydramine can cause strong sedation and has also been used as an anxiolytic as a result. It has also proven to have mild antiobsessive effects in one study researching obsessive–compulsive disorder (OCD) medication. Originally intended to act as a control medication, it in fact produced a significant decrement in OCD symptoms. Because of these sedative properties, diphenhydramine is widely used in nonprescription sleep aids for insomnia. The maximum recommended dose is 50 mg (as the hydrochloride salt), as mandated by the U.S. FDA. The drug is an ingredient in several products sold as sleep aids, either alone or in combination with other ingredients such as acetaminophen (paracetamol). An example of the latter is Tylenol PM. Examples of products having diphenhydramine as the only active ingredient include Unisom (of which one variety uses diphenhydramine, while another uses doxylamine), Tylenol Simply Sleep, Nytol, ZzzQuil, and Sominex (the version sold in the US and Canada; that sold in the UK uses promethazine). Tolerance against the sedating effect of diphenhydramine builds very quickly; after three days of use at the common dosage, it is no more effective than a placebo (according to one study done with 15 subjects). Diphenhydramine can cause minor psychological dependence when used improperly. Diphenhydramine also has antiemetic properties, which make it useful in treating the nausea that occurs in motion sickness. As it causes marked sedation in many individuals, newer-generation antihistamines, such as meclizine, may be preferred for antiemetic use. Also, topical formulations of diphenhydramine are available, including creams, lotions, gels, and sprays. These are used to relieve itching, and have the advantage of causing fewer systemic effects (e.g., drowsiness) than oral forms. Diphenhydramine also has local anesthetic properties, and has been used as such in patients allergic to common local anesthetics such as lidocaine. Various derivatives of diphenhydramine including the muscle relaxant orphenadrine (Norflex) and bromodiphenhydramine (Ambrodyl) are used clinically and in research. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「diphenhydramine」の詳細全文を読む スポンサード リンク
|