arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.cimetidinecimetidine will increase the level or effect of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.cinnarizinecinnarizine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.citaloprammethamphetamine, citalopram. Either increases effects of the other by unknown mechanism. Use Caution/Monitor. Risk of serotonin syndrome.clemastineclemastine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.clobazamclobazam will increase the level or effect of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Lower doses of drugs metabolized by CYP2D6 may be required when used concomitantly. clomipramineclomipramine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.clonazepamclonazepam increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.clorazepateclorazepate increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.clozapineclozapine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.codeinecodeine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.cyclizinecyclizine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.cyproheptadinecyproheptadine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.darifenacindarifenacin will increase the level or effect of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.desipraminedesipramine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.desvenlafaxinedesvenlafaxine will increase the level or effect of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Desvenlafaxine inhibits CYP2D6; with higher desvenlafaxine doses (ie, 400 mg) decrease the CYP2D6 substrate dose by up to 50%; no dosage adjustment needed with desvenlafaxine doses <100 mgdexchlorpheniraminedexchlorpheniramine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.dexfenfluraminemethamphetamine and dexfenfluramine both decrease sedation. Use Caution/Monitor.dexfenfluramine and methamphetamine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.dexmedetomidinedexmedetomidine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.dexmethylphenidatedexmethylphenidate and methamphetamine both decrease sedation. Use Caution/Monitor.dexmethylphenidate and methamphetamine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.dextroamphetaminedextroamphetamine and methamphetamine both decrease sedation. Use Caution/Monitor.dextroamphetamine and methamphetamine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.dextroamphetamine transdermalmethamphetamine, dextroamphetamine transdermal. Either increases effects of the other by serotonin levels. Modify Therapy/Monitor Closely. Initiate with lower doses and monitor for signs and symptoms of serotonin syndrome, particularly during initiation or dosage increase. If serotonin syndrome occurs, discontinue dextroamphetamine transdermal and concomitant serotonergic drug(s).dextromoramidedextromoramide increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.diamorphinediamorphine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.diazepamdiazepam increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.diethylpropionmethamphetamine and diethylpropion both decrease sedation. Use Caution/Monitor.diethylpropion and methamphetamine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.difenoxin hcldifenoxin hcl increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.diltiazemmethamphetamine will decrease the level or effect of diltiazem by pharmacodynamic antagonism. Use Caution/Monitor. Amphetamines may diminish antihypertensive effects of diltiazem. Monitor BP.dimenhydrinatedimenhydrinate increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.diphenhydraminediphenhydramine will increase the level or effect of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.diphenhydramine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.diphenoxylate hcldiphenoxylate hcl increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.dipipanonedipipanone increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.dobutaminedobutamine and methamphetamine both decrease sedation. Use Caution/Monitor.dobutamine and methamphetamine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.dopaminemethamphetamine and dopamine both decrease sedation. Use Caution/Monitor.dopamine and methamphetamine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.dopexaminedopexamine and methamphetamine both decrease sedation. Use Caution/Monitor.dopexamine and methamphetamine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.doxepindoxepin increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.dronedaronedronedarone will increase the level or effect of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.droperidoldroperidol increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.droxidopamethamphetamine and droxidopa both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. May increase risk for supine hypertensionduloxetineduloxetine will increase the level or effect of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely.eliglustateliglustat increases levels of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Monitor therapeutic drug concentrations, as indicated, or consider reducing the dosage of the concomitant drug and titrate to clinical effect.elvitegravir/cobicistat/emtricitabine/tenofovir DFelvitegravir/cobicistat/emtricitabine/tenofovir DF increases levels of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Cobicistat is a CYP2D6 inhibitor; caution with CYP2D6 substrates for which elevated plasma concentrations are associated with serious and/or life-threatening events.ephedrineephedrine and methamphetamine both decrease sedation. Use Caution/Monitor.ephedrine and methamphetamine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.ephedrine, methamphetamine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor.epinephrineepinephrine and methamphetamine both decrease sedation. Use Caution/Monitor.epinephrine and methamphetamine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.epinephrine inhaledmethamphetamine, epinephrine inhaled. Either increases effects of the other by sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.epinephrine racemicepinephrine racemic and methamphetamine both decrease sedation. Use Caution/Monitor.epinephrine racemic and methamphetamine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.esketamine intranasalesketamine intranasal, methamphetamine. Either increases toxicity of the other by sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. Closely monitor blood pressure with concomitant use of esketamine nasal with stimulants. .estazolamestazolam increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.ethanolethanol increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.fedratinibfedratinib will increase the level or effect of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Adjust dose of drugs that are CYP2D6 substrates as necessary.fenfluraminemethamphetamine and fenfluramine both decrease sedation. Use Caution/Monitor.fenfluramine and methamphetamine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.fluphenazinefluphenazine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.fluphenazine, methamphetamine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.flurazepamflurazepam increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.formoterolformoterol and methamphetamine both decrease sedation. Use Caution/Monitor.formoterol and methamphetamine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.green teagreen tea, methamphetamine. Other (see comment). Use Caution/Monitor. Comment: Green tea may include caffeine. Caffeine is a CNS-stimulant and additive effects may be seen when coadministered with other CNS stimulants. Caffeine should be avoided or used cautiously.haloperidolhaloperidol will increase the level or effect of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.haloperidol increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.hydralazinehydralazine, methamphetamine. Mechanism: pharmacodynamic antagonism. Use Caution/Monitor. Sympathomimetics can antagonize the activity of some antihypertensive agents.hydrocodonehydrocodone, methamphetamine. Either increases effects of the other by serotonin levels. Use Caution/Monitor. Coadministration of drugs that affect the serotonergic neurotransmitter system may result in serotonin syndrome. If concomitant use is warranted, carefully observe the patient, particularly during treatment initiation and dose adjustment.hydromorphonehydromorphone increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.hydroxyzinehydroxyzine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.iloperidoneiloperidone increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.imatinibimatinib will increase the level or effect of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.imipramineimipramine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.ioflupane I 123methamphetamine decreases effects of ioflupane I 123 by receptor binding competition. Use Caution/Monitor. Drugs that bind to dopamine transporter receptor with high affinity may interfere with the image following ioflupane I 123 administration.isoproterenolisoproterenol and methamphetamine both decrease sedation. Use Caution/Monitor.isoproterenol and methamphetamine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.ketotifen, ophthalmicketotifen, ophthalmic increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.levalbuterollevalbuterol and methamphetamine both decrease sedation. Use Caution/Monitor.levalbuterol and methamphetamine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.levorphanollevorphanol increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.lisdexamfetaminelisdexamfetamine and methamphetamine both decrease sedation. Use Caution/Monitor.lisdexamfetamine and methamphetamine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.lofepraminelofepramine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.lofexidinelofexidine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.loprazolamloprazolam increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.lorazepamlorazepam increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.lorcaserinlorcaserin will increase the level or effect of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.lormetazepamlormetazepam increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.loxapineloxapine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.loxapine inhaledloxapine inhaled increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.maprotilinemaprotiline increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.maravirocmaraviroc will increase the level or effect of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.marijuanamarijuana will increase the level or effect of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.marijuana increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.melatoninmelatonin increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.meperidinemeperidine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.meprobamatemeprobamate increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.metaproterenolmetaproterenol and methamphetamine both decrease sedation. Use Caution/Monitor.metaproterenol and methamphetamine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.metforminmethamphetamine decreases effects of metformin by pharmacodynamic antagonism. Use Caution/Monitor. Patient should be closely observed for loss of blood glucose control; when drugs are withdrawn from a patient receiving metformin, patient should be observed closely for hypoglycemia.methadonemethadone increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.methyldopamethyldopa increases effects of methamphetamine by unknown mechanism. Use Caution/Monitor.methylenedioxymethamphetaminemethamphetamine and methylenedioxymethamphetamine both decrease sedation. Use Caution/Monitor.methamphetamine and methylenedioxymethamphetamine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.methylphenidatemethamphetamine increases effects of methylphenidate by pharmacodynamic synergism. Use Caution/Monitor. Risk of acute hypertensive episode.midazolammidazolam increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.midodrinemethamphetamine and midodrine both decrease sedation. Use Caution/Monitor.methamphetamine and midodrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.mirabegronmirabegron will increase the level or effect of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.mirtazapinemirtazapine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.modafinilmethamphetamine and modafinil both decrease sedation. Use Caution/Monitor.morphinemorphine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.motherwortmotherwort increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.moxonidinemoxonidine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.nabilonenabilone increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.nalbuphinenalbuphine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.nilotinibnilotinib will increase the level or effect of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.norepinephrinenorepinephrine and methamphetamine both decrease sedation. Use Caution/Monitor.norepinephrine and methamphetamine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.nortriptylinenortriptyline increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.olanzapineolanzapine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.opium tinctureopium