Quinidine Dextromethorphan

Anon Dextromethorphan/quinidine AVP 923, dexiromethorphan/cytochrome P450-2D6 inhibitor, quinidine/dextromethorphan. Drugs R D (2005) 6,174-7. 

Codeine, dextromethorphan, haloperidol, thioridazine, perphenazine, nortriptyline, desipramine, fluoxetine, norfluoxetine, TCAs (hydroxylation), beta-blockers such as timolol and metoprolol, type 1C antiarrhythmics encainide, flecainide TCAs (desmethylation), triazolam, alprazolam, midazolam, carbamazepine, terfenadine, quinidine, lidocaine, erythromycin, cyclosporin... 

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. 

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,... 

CYP2D6 Dextromethorphan 0.44-8.5 AMMC 1.5 Quinidine 1 pM Higher concentrations can affect... 

Memantine is not a major substrate for hepatic cytochrome P450 isoenzymes and has not been shown to significantly inhibit or induce these enzymes. However, memantine is partially excreted by renal tubular secretion. Thus, concomitant use of other medications that use the same renal system (i.e., triampterene, hydrochlorothiazide, digoxin, cimetidine, ranitidine, metformin, and quinidine) may affect plasma levels of both drugs (Namenda 2005). Memantine should not be used in combination with other NMDA receptor antagonists, such as amantadine or dextromethorphan, because these combinations have not been formally studied. The clearance of memantine can be reduced when the urine is alkalinized, such as with the concomitant use of sodium bicarbonate or carbonic anhy-... 

D6 Bufuralol, bupranolol, clomipramine, clozapine, codeine, debrisoquin, dextromethorphan, encainide, flecainide, fluoxetine, guanoxan, haloperidol, hydrocodone, 4-methoxy-amphetamine, metoprolol, mexile-tine, oxycodone, paroxetine, phenformin, propafenone, propoxyphene, risperidone, selegiline (deprenyl), sparteine, thioridazine, timolol, tricyclic antidepressants Unknown Quinidine, paroxetine... 

D6 Debrisoquine, sparteine, bufuralol, propanolol, thioridazine, quinidine, phenytoin, fluoxetine NNK3 Dextromethorphan, [bufuralol (4 -OH)... 

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. 

Pope LE, Khalil MH, Berg JE, et al. Pharmacokinetics of dextromethorphan after single or multiple dosing in combination with quinidine in extensive and poor metabolizers. J Clin Pharmacol 2004 44 1132-1142. 

Capon DA, Bochner F, Kerry N, et al. The influence of CYP2D6 polymorphism and quinidine on the disposition and antitussive effect of dextromethorphan in humans. Clin Pharmacol Ther 1996 60 295-307. 

D6 Desipramine, dextromethorphan, atomoxetine Paroxetine, quinidine, fluoxetine (use of PM vs. EM subjects) None identified... 

C19 2D6 Mephenytoin (4-hydroxy metabolite), Omeprazole Bufuralol, Dextromethorphan Metoprolol, Debrisquine, Codeine Tranylcypromine Quinidine Ticlopidine (but also inhibits 2D6), Nootkatone (but also inhibits 2A6)... 

In ALS, emotional lability or pseudobulbar affect can limit social interactions and quality of life. While there are no currently FDA approved therapies for pseudobulbar affect in ALS, SSRIs, tricylic antidepressants and dopaminergic therapy can be beneficial (Gordon and Mitsumoto, 2006). One randomized controlled trial showed that a combination of dextromethorphan and quinidine reduced emotional lability and improved quality of life in ALS (Brooks et al., 2004). 

Pseudobulbar affect SSRI antidepressants 20-100 mg QD Tricyclic antidepressants 20-100 mg QHS Mirtazapine 15-30 mg QHS Venlafaxine 37.5-75 mg BID-TID Dextromethorphan/quinidine 30mg/30mg BID Lithium carbonate 300 mg QD-TID... 

Brooks BR, Thisted RA, Appel SH, Bradley WG, Olney RK, Berg JE, Pope LE, Smith RA AVP-923 ALS Study Group (2004) Treatment of pseudobulbar affect in ALS with dextromethorphan and quinidine. Neurology 63 1363-1373. 

The effects of quinidine sulfate, 50 mg orally, an inhibitor of cytochrome CYP2D6, on the metabolism of dextromethorphan 50 mg have been studied in seven healthy volunteers in a randomized, double-blind, crossover, placebo-controlled study (24). Quinidine suppressed the conversion of dextromethorphan to dextrorphan in extensive metabolizers to the extent seen in poor metabolizers. The increased concentrations of dextromethorphan increased subjective and objective pain thresholds by 35 and 45 % respectively. This result suggests that debriso-quine/sparteine-type polymorphisms account for important differences in the effect of dextromethorphan and the balance between the analgesic effect of dextromethorphan and the hallucinogenic effect of dextrorphan. Concomitant use of quinidine or other inhibitors of CYP2D6 could... 

Genetic polymorphisms in CYP450 isoenzymes are common. Among whites, 5-10% of the population carries a mutation of CYP450 2D6, causing them to be slow metabolizers of debriso-quine, mephenytoin, quinidine, metoprolol and dextromethorphan standard doses are more likely to be associated with adverse events as a consequence, especially when a second substrate drag is interacting. 

CYP2D6 Metopronolol Imipramine Encainide Barbiturates Rifampin in EMs only Quinidine Yes Dextromethorphan Debrosoquine... 

Pharmacokinetics of dextromethorphan and metabolites in humans Influence of the CYP2D6 phenotype and quinidine inhibition. J Clin Psychopharmacology 15(5) 263-269, 1995. 

Acetaminophen, aldrin, alfentanil, amiodarone, aminopyrine, amitriptyline, amprenavir, androstenedione,antipyrine, astemizole, benzphetamine, budesonide, carbamazepine, celecoxib, chlorpromazine, chlorzoxazone, cisapride, clarithromycin, clozapine, cocaine, codeine, cortisol, cyclophosphamide,cyclosporin, dapsone, delavirdine, dextromethorphan, digitoxin, diltiazem, diazepam, erythromycin, 17j3-estradiol, ethinylestradiol, etoposide, felbamate, fentanyl, flutamide, hydroxyarginine, ifosphamide, imipramine, indinavir, ketoconazole, lansoprazole, loratidine, losartan, lovastatin, (iS)"mephen3d in, methadone, mianserin, miconazole, mifepristone, nelfinavir, nevirapine, nicardipine, nifedipine, odansetron, omeprazole, orphenadrine, proguanil, propafenone, quinidine, quinine, rapamycin, retinoic acid, ritonavir, saquinavir, selegiline, serindole, sufentanil, sulfinpyrazone, tacrolimus, tamoxifen, tamsulosin, taxol, teniposide, terfenadine, tetrahydrocannabinol, theophylline, toremifene, triazolam, trimethadone, trimethoprim, troleandomycin, verapamil, warfarin, zatosetron, Zolpidem, zonisamide... 

Extracted amoxapine, brompheniramine, chlorpheniramine, chlorpromazine, clomipramine, c5q)roheptadine, dsipramine, diphenhydramine, dothiepin, doxepin, fluoxetine, hal-operidol, imipramine, loxapine, maprotihne, meperidine, mesoridazine, methadone, metoclopramide, mianserin, moclobemide, nomifensine, nordoxepin, norfluoxetine, norpropoxyphene, northiaden, nortriptyline, pentobarbital, pheniramine, propojgrphene, propranolol, protriptyline, quinidine, quinine, sulforidazine, thioridazine, thiothixene, tranylcypromine, trazodone, trihe q)henidyl, triprolidine Nonintetfering dextromethorphan, norphetidine, pheno benzamine, prochlorperazine, trifluoperazine... 

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