Dextromethorphan antitussive action

Codeine, dextromethorphan and pholcodine are opioid cough suppressants indicated for dry cough. Sedating antihistamines, such as diphenhydramine, tend to have an antitussive action as well. Vitamin C is not used in the management of cough but may be used as a prophylaxis against colds. 

Dextromethorphan is metabolized to dextrophan (Figure 34-40) by the cytochrome P4S0 isozyme 2D6 (GYP 2D6), which exhibits genetic polymorphism. Dextrophan also lacks analgesic activity, but it does retain antitussive action. Dextrophan may be responsible for the more pleasant psychotropic effects of high dose dextromethorphan, whereas the parent drug may cause dysphoria, sedation, and ataxia. Thus poor metabolizers (deficient in GYP 2D6 activity) may be less prone and extensive metabolizers more prone to continue the abuse of dextromethorphan. 

Antitussive action—independent of analgesia (e.g., dextromethorphan) and at subanalgesic doses with codeine. 

Dextromethorphan HBr is the ( + )-isomer of the 3-methoxy form of the synthetic opioid levorphanol. It lacks the analgesic, respiratory depressant, and abuse potential of p opioid agonists but retains the centrally acting antitussive action. Dextromethorphan is not an opioid and is not listed in the Controlled Substances Act. Its effectiveness as an antitussive is less than that of codeine. Dextromethorphan is available in a number of nonprescription cough formulations. 

Nonnarcotic Antitussives. The most centrally active, noimarcotic antitussive is dextromethorphan [125-71-3] (39). It is similar to codeine in terms of potency and mechanism of action, ie, it is a direct depressant of the cough center. It is unique in that even though it is stmcturaHy related to codeine, it is not addictive. 

Dextromethorphan is an opioid antitussive similar in action to codeine and pholcodine. Codeine and pholcodine are considered to be more potent than dextromethorphan. Dextromethorphan tends to cause less constipation and dependence than codeine. Cough suppressants are not usually recommended in children under 2 years. 

Pharmacology Dextromethorphan is the d-isomer of the codeine analog of levorphanol. Its cough suppressant action is due to a central action on the cough center in the medulla. Dextromethorphan 15 to 30 mg equals 8 to 15 mg codeine as an antitussive. 

Dextromethorphan (Mediquell, Benylin DM, PediaCare 1, Delsym, Others) [OTC] [Antitussive] Uses Control nonproductive cough Action Suppresses medullary cough center Dose Adults. 10-30 mg PO q4h PRN (max 120 mg/24 h) Peds. 2-6 y 2.5-7.5 mg q4-8h (max 30 mg/24 h) 7-12 y 5-10 mg q4-8h (max 60 mg/24/h) Caution [C, /-] Not for persistent or chronic cough Contra < 2 y. Disp Caps, lozenges, syrup, Liq SE GI disturbances Interactions T Effects W/ amiodarone, fluoxetine, quinidine, terbinafme T risk of serotonin synd Wf sibutramine, MAOIs T CNS depression Wf antihistamines, antidepressants, sedative, opioids, EtOH EMS Will not affect cough caused by asthma,... 

Dextromethorphan is the dextrorotatory stereoisomer of a methylated derivative of levorphanol. It is purported to be free of addictive properties and produces less constipation than codeine. The usual antitussive dose is 15-30 mg three or four times daily. It is available in many over-the-counter products. Dextromethorphan has also been found to enhance the analgesic action of morphine and presumably other -receptor agonists. However, abuse of its purified (powdered) form has been reported to lead to serious adverse events including death. 

Dextromethorphan hydrobromide is an antitussive drug with no analgesic or addictive action. Its antitussive effect is similar to codeine. The recommended oral dose for adults is 10-30mg three to six times a day, not to exceed 120mg daily. It is absorbed rapidly and completely when taken orally with a lag time of 15-30 min [72]. 

Dextromethorphan is a nonnarcotic antitussive agent, which suppresses cough by central action. It is used for temporary relief of minor sore throat and temporary reduction in cough caused by minor throat and bronchial irritation. 

Dextromethorphan Dextromethorphan is the dextro- isomer of codeine. It is included in cough medicine because of its centrally acting antitussive effects. Dextromethorphan actions are unaffected by narcotic antagonists. It causes little sedation or Gl disturbances. 

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