デキストロメトルファン

用途

デキストロメトルファン（Dextromethorphan 、DXM）は鎮咳去痰薬の一つであり、鎮静作用および解離作用を持つモルフィナン系薬物である。商品名メジコンで販売されている。後発医薬品が販売されているほか、風邪薬や鎮咳薬の成分として一般用医薬品にも含まれている。そのほか、鎮痛剤またはオピオイド増強剤としてペインクリニックで用いられたり、依存症の治療での心理学的特性を持つ。剤形としては、錠剤、散剤、シロップ剤、トローチ剤（海外）である。通常臭化水素酸塩水和物として使用されるが、イオン交換樹脂であるポリスチレンスルホン酸に吸着させた製剤もある。純粋な状態では白色粉末で、味は苦い。

効能

鎮咳薬

化学的特性

Dextromethorphan is a white to slightly yellow, odorless, crystalline powder. The hydrobromide salt of dextromethorphan occurs as white crystals or a white crystalline powder, soluble in water, alcohol, and chloroform. It acts upon the central nervous system to suppress the cough reflex.

使用

Dextromethorphan is used therapeutically as an over-thecounter cough suppressant and antitussive. It is also commonly abused particularly by adolescents because of its relative ease of availability.

定義

ChEBI: Dextromethorphan is a 6-methoxy-11-methyl-1,3,4,9,10,10a-hexahydro-2H-10,4a-(epiminoethano)phenanthrene in which the sterocenters at positions 4a, 10 and 10a have S-configuration. It is a prodrug of dextrorphan and used as an antitussive drug for suppressing cough. It has a role as a NMDA receptor antagonist, a neurotoxin, a xenobiotic, an environmental contaminant, an antitussive, a prodrug and a oneirogen. It is functionally related to a dextrorphan. It is an enantiomer of a levomethorphan.

適応症

Dextromethorphan is used in treating nonproductive cough. It is available widely in a variety of nonprescription forms, such as capsules, lozenges, syrups, extended-release oral suspension, and chewable tablets. This drug possesses a pronounced anticough effect and minimal action on the CNS. It is not addictive.

生物学の機能

Dextromethorphan hydrobromide is the D-isomer of levorphanol. It lacks CNS activity but acts at the cough center in the medulla to produce an antitussive effect. It is half as potent as codeine as an antitussive. Anecdotal reports of abuse exist, but studies of abuse potential are lacking. It has few side effects but does potentiate the activity of monoamine oxidase inhibitors, leading to hypotension and infrequently coma. Dextromethorphan is often combined in lozenges with the local anesthetic benzocaine, which blocks pain from throat irritation due to coughing.

一般的な説明

Dextromethorphan is the dextrorotatory form of levorphanolwith a methoxy group on the 3-position. It is availablein more than 140 over-the-counter (OTC) cough and coldformulations. Evidence-based reviews have been unable toconclude that it is more effective than placebo in reducingcough. Like (+) and (-) levorphanol, (+) dextromethorphanis a potent NMDA antagonist and, in higher than recommendeddoses, has the potential for causing dissociativeanesthetic effects similar to ketamine or phencyclidine (PCP).The OTC status and availability of pure dextromethorphanpowder online has contributed greatly to its abuse in recentyears. DAWN reports that in 2004, there were approximately12,500 emergency room visits involving dextromethorphanwith 44% of those involving abuse of the drug. The 2006National Survey on Drug Abuse report shows that nearly 1million persons aged 12 to 25 years (1.7%) misused OTCcough and cold medications in the past year.
Dextromethorphan’s ability to antagonize the NMDA receptorhas led to its use to treat phantom pain, diabetic neuropathy,and postoperative acute pain.

環境運命予測

Dextromethorphan is the D-isomer of the codeine analog, methorphan. Unlike the L-isomer, it has no analgesic or addictive properties and does not act through the opioid receptors. The exact mechanism for the antitussive effect by dextromethorphan remains unclear and is likely multifactorial. Dextromethorphan is known to be an N-methyl-D-aspartate (NMDA) receptor antagonist; however, dextromethorphan binding sites are not limited to the known distribution of NMDA receptors.
Dextromethorphan’s main metabolite, dextrorphan, has NMDA receptor antagonist properties similar to ketamine and phencyclidine. This NMDA receptor antagonism is believed to result in a decreased reuptake of catecholamines. Dextromethorphan also inhibits the reuptake of serotonin. These properties make dextromethorphan have a high abuse and misuse potential.
Dextromethorphan is a common ingredient in over-thecounter cough and cold preparations, and is often combined with other agents including concurrent antihistamines, decongestants, analgesics, and ethanol. Patients may exhibit toxicity due to these coingestants.