Dextromethorphan drug interactions

Dextromethorphan is known to interact with quini-dine and terbinafine. In both cases, there is a reduction in the metabolism of dextromethorphan by the liver. Terbinafine is a drug used to treat fungal infections. Quinidine is used for the treatment of malarial infections and heart rhythm problems. There has been a case report of a drug interaction between the use of fluoxetine (Prozac) and dextromethorphan. Fluoxetine is an antidepressant in the class of drugs called serotonin reuptake inhibitors. 

There is a wide choice of dmgs that are substrates for CYP2D6, but sparteine, debrisoquine, desipramine, dextromethorphan, and metoprolol have been used most frequently, both in vitro and in vivo. One advantage for in vivo drug-drug interaction studies is that most of the substrates were identified in the clinic rather than by the use of a battery of in vitro methods. 

Eap CB, Bondolfi G, Zullino D, Bryois C, Fuciec M, Savary L, Jonzier-Perey M, Baumann P. Pharmacokinetic drug interaction potential of risperidone with cytochrome p450 isozymes as assessed by the dextromethorphan, the caffeine, and the mephenytoin test. Ther Drug Monit 2001 23(3) 228-31. 

The opioids (e.g. codeine, dextromethorphan), NSAIDs, aspirin and paracetamol found in many over-the-counter drugs have the potential for adverse drug interactions. For more details, see Over-the-Counter Drugs. 

Many drug compounds are racemic mixtures of stereoisomers. In most cases, one of the isomers is more pharmacologically active than the other isomer, and each isomer may exhibit different pharmacokinetic properties. Warfarin, propranolol, verapamil, and ibuprofen are aU racemic mixtures of stereoisomers. Some drug interactions inhibit or increase the elimination of only one stereoisomer. The importance of the drug interaction depends on which isomer is affected. Other drugs, such as dextromethorphan, levofloxacin, and dUtiazem, are composed of just one stereoisomer. 

The risk of serotonin syndrome may be increased shortly after dosage increases of SSRIs or when drug interactions increase serotonin activity. Concomitant or proximal use of SSRIs, tricyclic antidepressants, or monoamine oxidase inhibitors may cause serotonin syndrome. Further, the addition of certain drugs, such as tryptophan, dextromethorphan, cocaine, or sympathomimetics, to SSRI therapy may increase the risk of developing serotonin syndrome." ... 

Drug interactions serotonin syndrome includes diaphoresis, rigidity, myoclonus, hyperthermia, ANS instability, and seizures. Has been reported for SSRIs when used with MAOIs, TCAs, meperidine, and dextromethorphan. 

Vengurlekar, S.S. et al., A sensitive LC-MS/MS assay for the determination of dextromethorphan and metabolites in human urine—Application for drug interaction studies assessing potential CYP3A and CYP2D6 inhibition, J. Pharm. Biomed. Anal., 30(1), 113,2002. 

Drug interactions serotonin syndrome with MAO inhibitors, TCAs, meperidine and dextromethorphan... 

Drug-drug interactions The inhibitory effect of bupropion on CYP2D6 metabolism has been previously demonstrated in vivo, for example by inhibition of dextromethorphan metabolism (SEDA-30, 20). An in vitro study using desipramine as substrate has suggested that this effect is due to the metabolites erythrohydrobupropion and threohydrobupropion, which were much more potent inhibitors of CYP2D6 than hydroxybupropion or bupropion itself [71 ]. 

P.J.R. Roche, S.M. Ng, R. Narayanaswamy, N. Goddard and K.M. Page, Multiple surface plasmon resonance quantification of dextromethorphan using a molecularly imprinted beta-cyclodextrin polymer A potential probe for drug-drug interactions. Sens. Actuat B-Chem., 139 (1) 22-29,2009. 

Drugs that may affect amiodarone include hydantoins, cholestyramine, fluoroquinolones, rifamycins, ritonavir, and cimetidine. Drugs that may be affected by amiodarone include anticoagulants, beta-blockers, calcium channel blockers, cyclosporine, dextromethorphan, digoxin, disopyramide, fentanyl, flecainide, hydantoins, lidocaine, methotrexate, procainamide, quinidine, and theophylline. Drug/Lab test interactions Amiodarone alters the results of thyroid function tests, causing an increase in serum T4 and serum reverse T3 levels and a decline in... 

Drugs that may interact with dextromethorphan include MAO inhibitors, quinidine, and sibutramine. 

Drugs that may interact with terbinafine include the following Cimetidine, rifampin, terfenadine, caffeine, dextromethorphan, cyclosporine. 

Memantine (Namenda) [Anti Alzheimer Agent/NMDA Receptor Antagonist] Uses Mod/ evere Alzheimer Dz Action N-methyl-D-aspartate recqjtor antagonist Dose Target 20 mg/d, start 5 mg/d, t 5 mg/d to 20 mg/d, wait >1 wk before t dose use doses if >5mg/d Caution [B, /-] Hqjatic/mild-mod renal impair Disp Tabs, sol SE Dizziness Interactions t Effects W amantadine, carbonic anhydrase inhibitors, dextromethorphan, ketamine, Na bicarbonate t effects W/ any drug, herb, food that alkalinizes urine EMS Use NaHCOs w/ caution OD May cause restlessness, hallucinations, drowsiness, and fainting symptomatic and supportive... 

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