(1)lefamulin and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.lemborexantMonitor Closely (1)lemborexant will increase the level or effect of thioridazine by sedation. Modify Therapy/Monitor Closely. Dosage adjustment may be necessary if lemborexant is coadministered with other CNS depressants because of potentially additive effects.lenvatinibMonitor Closely (1)thioridazine and lenvatinib both increase QTc interval. Use Caution/Monitor. Lenvatinib prescribing information recommends monitoring ECG closely when coadministered with QT prolonging drugs.leuprolideContraindicated (1)leuprolide increases toxicity of thioridazine by QTc interval. Contraindicated. Increases risk of torsades de pointes.levalbuterolMonitor Closely (1)thioridazine increases and levalbuterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.levodopaSerious - Use Alternative (1)thioridazine decreases effects of levodopa by pharmacodynamic antagonism. Avoid or Use Alternate Drug.levodopa inhaledSerious - Use Alternative (1)thioridazine decreases effects of levodopa inhaled by pharmacodynamic antagonism. Avoid or Use Alternate Drug. Phenothiazine/1st generation antipsychotics inhibit dopamine D2 receptors in varying degrees.levofloxacinMonitor Closely (1)thioridazine and levofloxacin both increase QTc interval. Modify Therapy/Monitor Closely.levoketoconazoleSerious - Use Alternative (1)thioridazine and levoketoconazole both increase QTc interval. Avoid or Use Alternate Drug.levorphanolMonitor Closely (1)levorphanol and thioridazine both increase sedation. Use Caution/Monitor.liraglutideMonitor Closely (1)thioridazine, liraglutide. Other (see comment). Use Caution/Monitor. Comment: Phenothiazines may increase or decrease glucose levels, monitor therapy closely when these agents are concurrently administered.lisdexamfetamineMonitor Closely (2)thioridazine, lisdexamfetamine. 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. thioridazine increases and lisdexamfetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.lisinoprilMinor (1)thioridazine increases effects of lisinopril by unspecified interaction mechanism. Minor/Significance Unknown.lisurideSerious - Use Alternative (1)thioridazine decreases effects of lisuride by pharmacodynamic antagonism. Contraindicated.lithiumContraindicated (1)lithium and thioridazine both increase QTc interval. Contraindicated.Monitor Closely (1)lithium, thioridazine. Other (see comment). Use Caution/Monitor. Comment: Risk of neurotoxicity. Multiple mechanisms involved.lofepramineMonitor Closely (2)thioridazine will increase the level or effect of lofepramine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. thioridazine and lofepramine both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)thioridazine and lofepramine both increase QTc interval. Avoid or Use Alternate Drug.Minor (2)lofepramine, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects. lofepramine, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.lofexidineMonitor Closely (3)thioridazine and lofexidine both increase QTc interval. Use Caution/Monitor. ECG monitoring is recommended. thioridazine will increase the level or effect of lofexidine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Concomitant use of lofexidine with strong CYP2D6 inhibitors may increase lofexidine plasma levels. Monitor for symptoms of orthostasis and bradycardia if coadministered with a CYP2D6 inhibitor. Consider lofexidine dose reduction. thioridazine and lofexidine both increase sedation. Use Caution/Monitor.lonapegsomatropinMonitor Closely (1)lonapegsomatropin will decrease the level or effect of thioridazine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Limited published data indicate that growth hormone treatment increases cytochrome P450 (CYP450)-mediated antipyrine clearance. Caution with sensitive CYP substratesloprazolamMonitor Closely (1)loprazolam and thioridazine both increase sedation. Use Caution/Monitor.loratadineMinor (1)thioridazine will increase the level or effect of loratadine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.lorazepamMonitor Closely (1)lorazepam and thioridazine both increase sedation. Use Caution/Monitor.lorcaserinMonitor Closely (1)lorcaserin will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.lormetazepamMonitor Closely (1)lormetazepam and thioridazine both increase sedation. Use Caution/Monitor.loxapineMonitor Closely (2)loxapine and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor. loxapine and thioridazine both increase sedation. Use Caution/Monitor.loxapine inhaledMonitor Closely (2)loxapine inhaled and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor. loxapine inhaled and thioridazine both increase sedation. Use Caution/Monitor.lumefantrineSerious - Use Alternative (2)lumefantrine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. thioridazine and lumefantrine both increase QTc interval. Avoid or Use Alternate Drug.lurasidoneMonitor Closely (1)lurasidone, thioridazine. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: Potential for increased CNS depressant effects when used concurrently; monitor for increased adverse effects and toxicity.macimorelinSerious - Use Alternative (1)macimorelin and thioridazine both increase QTc interval. Avoid or Use Alternate Drug. Macimorelin causes an increase of ~11 msec in the corrected QT interval. Avoid coadministration with drugs that prolong QT interval, which could increase risk for developing torsade de pointes-type ventricular tachycardia. Allow sufficient washout time of drugs that are known to prolong the QT interval before administering macimorelin.maprotilineMonitor Closely (1)thioridazine and maprotiline both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)thioridazine and maprotiline both increase QTc interval. Avoid or Use Alternate Drug.Minor (2)maprotiline, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects. maprotiline, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.maravirocSerious - Use Alternative (1)maraviroc will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.marijuanaMonitor Closely (1)thioridazine and marijuana both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)marijuana will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.meclizineMonitor Closely (3)meclizine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. meclizine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor. thioridazine increases effects of meclizine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.mefloquineSerious - Use Alternative (1)mefloquine increases toxicity of thioridazine by QTc interval. Avoid or Use Alternate Drug. Mefloquine may enhance the QTc prolonging effect of high risk QTc prolonging agents.melatoninMonitor Closely (1)thioridazine and melatonin both increase sedation. Use Caution/Monitor.meperidineMonitor Closely (1)meperidine and thioridazine both increase sedation. Use Caution/Monitor.meprobamateMonitor Closely (1)thioridazine and meprobamate both increase sedation. Use Caution/Monitor.metaproterenolMonitor Closely (1)thioridazine increases and metaproterenol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.metaxaloneMonitor Closely (1)metaxalone and thioridazine both increase sedation. Use Caution/Monitor.metforminMonitor Closely (1)thioridazine 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.methadoneMonitor Closely (2)thioridazine and methadone both increase QTc interval. Modify Therapy/Monitor Closely. methadone and thioridazine both increase sedation. Use Caution/Monitor.methamphetamineMonitor Closely (3)thioridazine will increase the level or effect of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. thioridazine, 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. thioridazine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.methocarbamolMonitor Closely (1)methocarbamol and thioridazine both increase sedation. Use Caution/Monitor.methoxsalenMonitor Closely (1)methoxsalen, thioridazine. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Additive photosensitizing effects.methscopolamineMonitor Closely (3)methscopolamine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. methscopolamine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor. thioridazine increases effects of methscopolamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.methyl aminolevulinateSerious - Use Alternative (1)thioridazine, methyl aminolevulinate. Either increases toxicity of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Each drug may increase the photosensitizing effect of the other.methyldopaSerious - Use Alternative (1)thioridazine decreases effects of methyldopa by pharmacodynamic antagonism. Contraindicated.methylenedioxymethamphetamineMonitor Closely (2)thioridazine, methylenedioxymethamphetamine. 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. thioridazine increases and methylenedioxymethamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.methylphenidateMonitor Closely (1)thioridazine, methylphenidate. 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.metoclopramideMonitor Closely (1)thioridazine and metoclopramide both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.metoclopramide intranasalSerious - Use Alternative (3)thioridazine will increase the level or effect of metoclopramide intranasal by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Concurrent use of metoclopramide intranasal and strong CYP2D6 inhibitors is not recommended since the metoclopramide intranasal dose cannot be adjusted. thioridazine, metoclopramide intranasal. Either increases effects of the other by Other (see comment). Avoid or Use Alternate Drug. Comment: Avoid use of metoclopramide intranasal or interacting drug, depending on importance of drug to patient. thioridazine increases toxicity of metoclopramide intranasal by pharmacodynamic synergism. Avoid or Use Alternate Drug. Potential for additive effects, including increased frequency and severity of tardive dyskinesia, other extrapyramidal symptoms, and neuroleptic malignant syndrome.metoprololMonitor Closely (1)thioridazine will increase the level or effect of metoprolol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.Serious - Use Alternative (1)metoprolol, thioridazine. Either increases levels of the other by decreasing metabolism. Contraindicated. Not all beta blockers share this interaction (e.g., atenolol, nadolol, sotalol do not interact).metrizamideContraindicated (1)thioridazine, metrizamide. Mechanism: unknown. Contraindicated. Risk of seizure. D/C phenothiazine 24h before admin. of metrizamide.metyraponeMinor (1)thioridazine decreases effects of metyrapone by unspecified interaction mechanism. Minor/Significance Unknown.metyrosineMinor (1)metyrosine increases toxicity of thioridazine by pharmacodynamic synergism. Minor/Significance Unknown. Increased extrapyramidal symptoms.mexiletineMonitor Closely (1)thioridazine will increase the level or effect of mexiletine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.midazolamMonitor Closely (1)midazolam and thioridazine both increase sedation. Use Caution/Monitor.midazolam intranasalMonitor Closely (1)midazolam intranasal, thioridazine. Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Concomitant use of barbiturates, alcohol, or other CNS depressants may increase the risk of hypoventilation, airway obstruction, desaturation, or apnea and may contribute to profound and/or prolonged drug effect.midodrineMonitor Closely (2)thioridazine, midodrine. 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. thioridazine increases and midodrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.mifepristoneContraindicated (1)mifepristone, thioridazine. QTc interval. Contraindicated.mirabegronMonitor Closely (1)mirabegron will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.mirtazapineContraindicated (1)mirtazapine and thioridazine both increase QTc interval. Contraindicated.Monitor Closely (1)thioridazine and mirtazapine both increase sedation. Use Caution/Monitor.mobocertinibSerious - Use Alternative (1)mobocertinib and thioridazine both increase QTc interval. Avoid or Use Alternate Drug. If coadministration unavoidable, reduce mobocertinib dose and monitor QTc interval more frequently.modafinilMonitor Closely (1)thioridazine increases and modafinil decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.moexiprilMinor (1)thioridazine increases effects of moexipril by unspecified interaction mechanism. Minor/Significance Unknown.morphineMonitor Closely (2)thioridazine will increase the level or effect of morphine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. morphine and thioridazine both increase sedation. Use Caution/Monitor.motherwortMonitor Closely (1)thioridazine and motherwort both increase sedation. Use Caution/Monitor.moxifloxacinSerious - Use Alternative (1)thioridazine and moxifloxacin both increase QTc interval. Avoid or Use Alternate Drug.moxonidineMonitor Closely (1)thioridazine and moxonidine both increase sedation. Use Caution/Monitor.nabiloneMonitor Closely (1)thioridazine and nabilone both increase sedation. Use Caution/Monitor.nalbuphineMonitor Closely (1)nalbuphine and thioridazine both increase sedation. Use Caution/Monitor.nebivololMonitor Closely (1)thioridazine will increase the level or effect of nebivolol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.nilotinibSerious - Use Alternative (2)thioridazine and nilotinib both increase QTc interval. Avoid or Use Alternate Drug. nilotinib will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.norepinephrineMonitor Closely (2)thioridazine, norepinephrine. 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. thioridazine increases and norepinephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.nortriptylineContraindicated (1)thioridazine will increase the level or effect of nortriptyline by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.Monitor Closely (1)thioridazine and nortriptyline both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)thioridazine and nortriptyline both increase QTc interval. Avoid or Use Alternate Drug.Minor (2)nortriptyline, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects. nortriptyline, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.octreotideSerious - Use Alternative (1)thioridazine and octreotide both increase QTc interval. Avoid or Use Alternate Drug.octreotide (Antidote)Serious - Use Alternative (1)thioridazine and octreotide (Antidote) both increase QTc interval. Avoid or Use Alternate Drug.ofloxacinMonitor Closely (1)thioridazine and ofloxacin both increase QTc interval. Modify Therapy/Monitor Closely.olanzapineContraindicated (1)olanzapine and thioridazine both increase QTc interval. Contraindicated.Monitor Closely (2)olanzapine and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor. olanzapine and thioridazine both increase sedation. Use Caution/Monitor.oliceridineMonitor Closely (2)thioridazine will increase the level or effect of oliceridine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. If concomitant use is necessary, may require less frequent oliceridine dosing. Closely monitor for respiratory depression and sedation and titrate subsequent doses accordingly. If inhibitor is discontinued, consider increase