Amphetamine may increase the serotonergic activities of Dextromethorphan. Moclobemide may increase the serotonergic activities of Dextromethorphan. The metabolism of Dextromethorphan can be decreased when combined with Capecitabine. The serum concentration of Dextromethorphan can be decreased when it is combined with Tocilizumab. The metabolism of Dextromethorphan can be decreased when combined with Pantoprazole. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Perospirone. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Ergotamine. The metabolism of Dextromethorphan can be decreased when combined with Isradipine. The metabolism of Dextromethorphan can be decreased when combined with Delavirdine. The serum concentration of Dextromethorphan can be decreased when it is combined with Siltuximab. The serum concentration of Thioridazine can be increased when it is combined with Dextromethorphan. The serum concentration of Dextromethorphan can be decreased when it is combined with Rilpivirine. The metabolism of Dextromethorphan can be decreased when combined with Tolbutamide. The serum concentration of Ledipasvir can be increased when it is combined with Dextromethorphan. The metabolism of Dextromethorphan can be decreased when combined with Eliglustat. Mebanazine may increase the serotonergic activities of Dextromethorphan. The metabolism of Dextromethorphan can be decreased when combined with Tipranavir. The metabolism of Dextromethorphan can be decreased when combined with Itraconazole. Dolasetron may increase the serotonergic activities of Dextromethorphan. Paroxetine may increase the serotonergic activities of Dextromethorphan. Pivhydrazine may increase the serotonergic activities of Dextromethorphan. The metabolism of Dextromethorphan can be decreased when combined with Clotrimazole. The metabolism of Dextromethorphan can be decreased when combined with Sildenafil. The risk or severity of adverse effects can be increased when Buspirone is combined with Dextromethorphan. The metabolism of Dextromethorphan can be decreased when combined with Gemfibrozil. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Tetrahydropalmatine. The metabolism of Dextromethorphan can be decreased when combined with Sorafenib. The metabolism of Dextromethorphan can be decreased when combined with Cocaine. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Lurasidone. The serum concentration of Dextromethorphan can be increased when it is combined with Ivacaftor. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Ritanserin. The metabolism of Dextromethorphan can be decreased when combined with Terbinafine. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Prochlorperazine. The serum concentration of Dextromethorphan can be decreased when it is combined with Peginterferon alfa-2b. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Sertindole. The metabolism of Dextromethorphan can be decreased when combined with Fluvastatin. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Paliperidone. The metabolism of Dextromethorphan can be decreased when combined with Boceprevir. Tedizolid Phosphate may increase the serotonergic activities of Dextromethorphan. Methylene blue may increase the serotonergic activities of Dextromethorphan. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Ecopipam. The serum concentration of Dextromethorphan can be increased when it is combined with Fusidic Acid. The metabolism of Dextromethorphan can be decreased when combined with Imatinib. Benmoxin may increase the serotonergic activities of Dextromethorphan. The risk or severity of adverse effects can be increased when Zolmitriptan is combined with Dextromethorphan. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Droperidol. The serum concentration of Dextromethorphan can be increased when it is combined with Luliconazole. The metabolism of Dextromethorphan can be decreased when combined with Clobazam. The metabolism of Dextromethorphan can be decreased when combined with Chloroquine. The risk or severity of adverse effects can be increased when Methadone is combined with Dextromethorphan. The metabolism of Dextromethorphan can be decreased when combined with Ziprasidone. The metabolism of Dextromethorphan can be decreased when combined with Dosulepin. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Tiapride. The metabolism of Dextromethorphan can be decreased when combined with Leflunomide. The risk or severity of adverse effects can be increased when Dihydroergotamine is combined with Dextromethorphan. Safrazine may increase the serotonergic activities of Dextromethorphan. L-Tryptophan may increase the serotonergic activities of Dextromethorphan. The metabolism of Dextromethorphan can be decreased when combined with Voriconazole. The serum concentration of Dextromethorphan can be increased when it is combined with Vemurafenib. The metabolism of Dextromethorphan can be increased when combined with Carbamazepine. The metabolism of Dextromethorphan can be decreased when combined with Quinine. The serum concentration of Conivaptan can be increased when it is combined with Dextromethorphan. Dapoxetine may increase the serotonergic activities of Dextromethorphan. The serum concentration of the active metabolites of Fesoterodine can be increased when Fesoterodine is used in combination with Dextromethorphan. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Amisulpride. The metabolism of Dextromethorphan can be decreased when combined with Etravirine. The metabolism of Dextromethorphan can be decreased when combined with Cholecalciferol. The metabolism of Dextromethorphan can be decreased when combined with Sulfamethoxazole. Etoperidone may increase the serotonergic activities of Dextromethorphan. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Trimipramine. The risk or severity of adverse effects can be increased when Vilazodone is combined with Dextromethorphan. Venlafaxine may increase the serotonergic activities of Dextromethorphan. The serum concentration of Vincristine can be increased when it is combined with Dextromethorphan. The serum concentration of Colchicine can be increased when it is combined with Dextromethorphan. The risk or severity of adverse effects can be increased when Mirtazapine is combined with Dextromethorphan. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Maprotiline. The metabolism of Dextromethorphan can be decreased when combined with Eslicarbazepine acetate. Brofaromine may increase the serotonergic activities of Dextromethorphan. The metabolism of Dextromethorphan can be decreased when combined with Methotrimeprazine. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Thioproperazine. The serum concentration of Dextromethorphan can be increased when it is combined with Aprepitant. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Remoxipride. The metabolism of Dextromethorphan can be decreased when combined with Modafinil. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Amperozide. The metabolism of Dextromethorphan can be decreased when combined with Sulfadiazine. The metabolism of Dextromethorphan can be decreased when combined with Ropinirole. The risk or severity of adverse effects can be increased when Trazodone is combined with Dextromethorphan. The serum concentration of Rifaximin can be increased when it is combined with Dextromethorphan. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Tapentadol. The serum concentration of Afatinib can be increased when it is combined with Dextromethorphan. The risk or severity of adverse effects can be increased when Eletriptan is combined with Dextromethorphan. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Metoclopramide. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Lithium. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Quetiapine. Pirlindole may increase the serotonergic activities of Dextromethorphan. The metabolism of Dextromethorphan can be increased when combined with Rifabutin. The metabolism of Dextromethorphan can be decreased when combined with Nelfinavir. The serum concentration of Dextromethorphan can be decreased when it is combined with Deferasirox. The serum concentration of Dextromethorphan can be increased when it is combined with Dasatinib. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Dapiprazole. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Promethazine. The serum concentration of Dextromethorphan can be decreased when it is combined with Enzalutamide. The metabolism of Dextromethorphan can be decreased when combined with Pyrimethamine. Isocarboxazid may increase the serotonergic activities of Dextromethorphan. The metabolism of Dextromethorphan can be decreased when combined with Artemether. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Bromocriptine. 7,8-Dichloro-1,2,3,4-tetrahydroisoquinoline may increase the serotonergic activities of Dextromethorphan. The metabolism of Dextromethorphan can be decreased when combined with Clarithromycin. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Fentanyl. The metabolism of Dextromethorphan can be decreased when combined with Celecoxib. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Linezolid. The metabolism of Dextromethorphan can be decreased when combined with Darifenacin. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Trifluoperazine. The metabolism of Dextromethorphan can be decreased when combined with Erythromycin. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Osanetant. The metabolism of Dextromethorphan can be increased when combined with Pentobarbital. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Reserpine. The serum concentration of Brentuximab vedotin can be increased when it is combined with Dextromethorphan. The metabolism of Dextromethorphan can be decreased when combined with Lovastatin. The metabolism of Dextromethorphan can be decreased when combined with Idelalisib. The serum concentration of Ranolazine can be increased when it is combined with Dextromethorphan. The metabolism of Dextromethorphan can be decreased when combined with Mirabegron. Phenoxypropazine may increase the serotonergic activities of Dextromethorphan. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Doxepin. The metabolism of Dextromethorphan can be decreased when combined with Fosamprenavir. The serum concentration of Dextromethorphan can be increased when it is combined with Panobinostat. The metabolism of Dextromethorphan can be decreased when combined with Losartan. The metabolism of Dextromethorphan can be decreased when combined with Rucaparib. The metabolism of Dextromethorphan can be decreased when combined with Atomoxetine. The risk or severity of adverse effects can be increased when Dextromethorphan is combined with Cyamemazine.