effects of homatropine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.hydrocodoneSerious - Use Alternative (1)hydrocodone, thiothixene. Either increases toxicity of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.hydromorphoneMonitor Closely (1)hydromorphone and thiothixene both increase sedation. Use Caution/Monitor.hydroxychloroquine sulfateSerious - Use Alternative (1)hydroxychloroquine sulfate and thiothixene both increase QTc interval. Avoid or Use Alternate Drug.hydroxyzineMonitor Closely (1)hydroxyzine and thiothixene both increase sedation. Use Caution/Monitor.hyoscyamineMonitor Closely (3)hyoscyamine decreases levels of thiothixene by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. hyoscyamine decreases levels of thiothixene by pharmacodynamic antagonism. Use Caution/Monitor. thiothixene increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.hyoscyamine sprayMonitor Closely (3)thiothixene increases effects of hyoscyamine spray by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia. hyoscyamine spray decreases levels of thiothixene by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. hyoscyamine spray decreases levels of thiothixene by pharmacodynamic antagonism. Use Caution/Monitor.iloperidoneMonitor Closely (2)iloperidone and thiothixene both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor. iloperidone and thiothixene both increase sedation. Use Caution/Monitor.imipramineMonitor Closely (1)thiothixene and imipramine both increase sedation. Use Caution/Monitor.incobotulinumtoxinAMonitor Closely (1)thiothixene increases effects of incobotulinumtoxinA by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.indacaterol, inhaledMonitor Closely (1)indacaterol, inhaled, thiothixene. QTc interval. Use Caution/Monitor. Drugs that are known to prolong the QTc interval may have an increased the risk of ventricular arrhythmias.ipratropiumMonitor Closely (3)ipratropium decreases levels of thiothixene by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. ipratropium decreases levels of thiothixene by pharmacodynamic antagonism. Use Caution/Monitor. thiothixene increases effects of ipratropium by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.isoproterenolMonitor Closely (1)thiothixene increases and isoproterenol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.ivosidenibSerious - Use Alternative (1)ivosidenib and thiothixene both increase QTc interval. Avoid or Use Alternate Drug. Avoid coadministration of QTc prolonging drugs with ivosidenib or replace with alternate therapies. If coadministration of a QTc prolonging drug is unavoidable, monitor for increased risk of QTc interval prolongation.ketamineMonitor Closely (1)ketamine and thiothixene both increase sedation. Use Caution/Monitor.ketotifen, ophthalmicMonitor Closely (1)thiothixene and ketotifen, ophthalmic both increase sedation. Use Caution/Monitor.lasmiditanMonitor Closely (1)lasmiditan, thiothixene. Either increases effects of the other by sedation. Use Caution/Monitor. Coadministration of lasmiditan and other CNS depressant drugs, including alcohol have not been evaluated in clinical studies. Lasmiditan may cause sedation, as well as other cognitive and/or neuropsychiatric adverse reactions.lemborexantMonitor Closely (1)lemborexant, thiothixene. Either increases effects of the other by sedation. Modify Therapy/Monitor Closely. Dosage adjustment may be necessary if lemborexant is coadministered with other CNS depressants because of potentially additive effects.levalbuterolMonitor Closely (1)thiothixene increases and levalbuterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.levodopaSerious - Use Alternative (1)thiothixene decreases effects of levodopa by pharmacodynamic antagonism. Avoid or Use Alternate Drug.levomilnacipranMonitor Closely (1)levomilnacipran, thiothixene. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).levorphanolMonitor Closely (1)levorphanol and thiothixene both increase sedation. Use Caution/Monitor.linezolidMonitor Closely (1)linezolid, thiothixene. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).lisdexamfetamineMonitor Closely (1)thiothixene increases and lisdexamfetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.lisurideSerious - Use Alternative (1)thiothixene decreases effects of lisuride by pharmacodynamic antagonism. Contraindicated.lithiumMonitor Closely (2)lithium, thiothixene. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction). lithium and thiothixene both increase QTc interval. Use Caution/Monitor.lofepramineMonitor Closely (1)thiothixene and lofepramine both increase sedation. Use Caution/Monitor.lofexidineMonitor Closely (1)thiothixene and lofexidine both increase sedation. Use Caution/Monitor.loprazolamMonitor Closely (1)loprazolam and thiothixene both increase sedation. Use Caution/Monitor.lorazepamMonitor Closely (1)lorazepam and thiothixene both increase sedation. Use Caution/Monitor.lorcaserinMonitor Closely (1)lorcaserin, thiothixene. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).lormetazepamMonitor Closely (1)lormetazepam and thiothixene both increase sedation. Use Caution/Monitor.loxapineMonitor Closely (2)loxapine and thiothixene both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor. loxapine and thiothixene both increase sedation. Use Caution/Monitor.loxapine inhaledMonitor Closely (2)loxapine inhaled and thiothixene both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor. loxapine inhaled and thiothixene both increase sedation. Use Caution/Monitor.lurasidoneMonitor Closely (1)lurasidone, thiothixene. 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 thiothixene 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)thiothixene and maprotiline both increase sedation. Use Caution/Monitor.maravirocMonitor Closely (1)maraviroc, thiothixene. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of orthostatic hypotension.marijuanaMonitor Closely (1)thiothixene and marijuana both increase sedation. Use Caution/Monitor.meclizineMonitor Closely (3)meclizine decreases levels of thiothixene by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. meclizine decreases levels of thiothixene by pharmacodynamic antagonism. Use Caution/Monitor. thiothixene increases effects of meclizine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.mefloquineSerious - Use Alternative (1)mefloquine increases toxicity of thiothixene by QTc interval. Avoid or Use Alternate Drug. Mefloquine may enhance the QTc prolonging effect of high risk QTc prolonging agents.melatoninMonitor Closely (1)thiothixene and melatonin both increase sedation. Use Caution/Monitor.meperidineMonitor Closely (2)meperidine, thiothixene. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction). meperidine and thiothixene both increase sedation. Use Caution/Monitor.meprobamateMonitor Closely (1)thiothixene and meprobamate both increase sedation. Use Caution/Monitor.metaproterenolMonitor Closely (1)thiothixene increases and metaproterenol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.metaxaloneMonitor Closely (1)metaxalone and thiothixene both increase sedation. Use Caution/Monitor.methadoneMonitor Closely (2)methadone, thiothixene. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction). methadone and thiothixene both increase sedation. Use Caution/Monitor.methamphetamineMonitor Closely (1)thiothixene increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.methocarbamolMonitor Closely (1)methocarbamol and thiothixene both increase sedation. Use Caution/Monitor.methscopolamineMonitor Closely (3)methscopolamine decreases levels of thiothixene by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. methscopolamine decreases levels of thiothixene by pharmacodynamic antagonism. Use Caution/Monitor. thiothixene increases effects of methscopolamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.methyldopaSerious - Use Alternative (1)thiothixene decreases effects of methyldopa by pharmacodynamic antagonism. Contraindicated.methylenedioxymethamphetamineMonitor Closely (1)thiothixene increases and methylenedioxymethamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.methylergonovineMonitor Closely (1)methylergonovine, thiothixene. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).methylphenidateMonitor Closely (1)thiothixene increases toxicity of methylphenidate by pharmacodynamic antagonism. Use Caution/Monitor. Closely monitor for signs of altered clinical response to either methylphenidate or an antipsychotic when using these drugs in combination.metoclopramideMonitor Closely (1)thiothixene and metoclopramide both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.metoclopramide intranasalSerious - Use Alternative (2)thiothixene, 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. thiothixene 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.metoprololSerious - Use Alternative (1)metoprolol, thiothixene. 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).midazolamMonitor Closely (1)midazolam and thiothixene both increase sedation. Use Caution/Monitor.midazolam intranasalMonitor Closely (1)midazolam intranasal, thiothixene. 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 (1)thiothixene increases and midodrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.mifepristoneMonitor Closely (1)mifepristone, thiothixene. QTc interval. Modify Therapy/Monitor Closely. Use alternatives if available.milnacipranMonitor Closely (1)milnacipran, thiothixene. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).mirtazapineMonitor Closely (1)thiothixene and mirtazapine both increase sedation. Use Caution/Monitor.mobocertinibSerious - Use Alternative (1)mobocertinib and thiothixene both increase QTc interval. Avoid or Use Alternate Drug. If coadministration unavoidable, reduce mobocertinib dose and monitor QTc interval more frequently.modafinilMonitor Closely (1)thiothixene increases and modafinil decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.morphineMonitor Closely (1)morphine and thiothixene both increase sedation. Use Caution/Monitor.motherwortMonitor Closely (1)thiothixene and motherwort both increase sedation. Use Caution/Monitor.moxonidineMonitor Closely (1)thiothixene and moxonidine both increase sedation. Use Caution/Monitor.nabiloneMonitor Closely (1)thiothixene and nabilone both increase sedation. Use Caution/Monitor.nalbuphineMonitor Closely (1)nalbuphine and thiothixene both increase sedation. Use Caution/Monitor.naratriptanMonitor Closely (1)naratriptan, thiothixene. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).norepinephrineMonitor Closely (1)thiothixene increases and norepinephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.nortriptylineMonitor Closely (1)thiothixene and nortriptyline both increase sedation. Use Caution/Monitor.olanzapineMonitor Closely (2)olanzapine and thiothixene both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor. olanzapine and thiothixene both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)olanzapine and thiothixene both increase QTc interval. Avoid or Use Alternate Drug.oliceridineMonitor Closely (1)oliceridine, thiothixene. Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.olodaterol inhaledMonitor Closely (1)thiothixene and olodaterol inhaled both increase QTc interval. Use Caution/Monitor. Drugs