the level or effect of lonafarnib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration of lonafarnib (a sensitive CYP3A substrate) with weak CYP3A inhibitors is unavoidable, reduce to, or continue lonafarnib at starting dose. Closely monitor for arrhythmias and events (eg, syncope, heart palpitations) since lonafarnib effect on QT interval is unknown.loxapineMonitor Closely (3)oxybutynin decreases levels of loxapine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. oxybutynin decreases levels of loxapine by pharmacodynamic antagonism. Use Caution/Monitor. loxapine increases effects of oxybutynin by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.loxapine inhaledMonitor Closely (2)loxapine inhaled increases effects of oxybutynin by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia. oxybutynin decreases levels of loxapine inhaled by pharmacodynamic antagonism. Use Caution/Monitor.lumefantrineMinor (1)lumefantrine will decrease the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.maprotilineMonitor Closely (1)oxybutynin and maprotiline both decrease cholinergic effects/transmission. Use Caution/Monitor.marijuanaMinor (1)marijuana will increase the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.meclizineMonitor Closely (1)meclizine and oxybutynin both decrease cholinergic effects/transmission. Use Caution/Monitor.methscopolamineMonitor Closely (1)methscopolamine and oxybutynin both decrease cholinergic effects/transmission. Use Caution/Monitor.methylprednisoloneMinor (1)methylprednisolone will decrease the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.metoclopramideMonitor Closely (1)oxybutynin decreases effects of metoclopramide by pharmacodynamic antagonism. Use Caution/Monitor. May antagonize prokinetic effects.metoclopramide intranasalSerious - Use Alternative (1)oxybutynin, 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.metronidazoleMinor (1)metronidazole will increase the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.miconazole vaginalMinor (1)miconazole vaginal will increase the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.midazolam intranasalMonitor Closely (2)oxybutynin will increase the level or effect of midazolam intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration of mild CYP3A4 inhibitors with midazolam intranasal may cause higher midazolam systemic exposure, which may prolong sedation. midazolam intranasal, oxybutynin. 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.nefazodoneMonitor Closely (1)nefazodone will increase the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.nelfinavirMinor (1)nelfinavir will increase the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.neostigmineMonitor Closely (1)neostigmine increases and oxybutynin decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.nevirapineMinor (1)nevirapine will decrease the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.nifedipineMinor (1)nifedipine will increase the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.nilotinibMinor (1)nilotinib will increase the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.nitrofurantoinMonitor Closely (1)oxybutynin increases levels of nitrofurantoin by unspecified interaction mechanism. Use Caution/Monitor.nortriptylineMonitor Closely (1)oxybutynin and nortriptyline both decrease cholinergic effects/transmission. Use Caution/Monitor.olanzapineMonitor Closely (3)oxybutynin decreases levels of olanzapine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. oxybutynin decreases levels of olanzapine by pharmacodynamic antagonism. Use Caution/Monitor. olanzapine increases effects of oxybutynin by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.olopatadine intranasalSerious - Use Alternative (1)oxybutynin and olopatadine intranasal both increase sedation. Avoid or Use Alternate Drug. Coadministration increases risk of CNS depression, which can lead to additive impairment of psychomotor performance and cause daytime impairment. onabotulinumtoxinAMonitor Closely (1)onabotulinumtoxinA and oxybutynin both decrease cholinergic effects/transmission. Use Caution/Monitor.orphenadrineMonitor Closely (1)oxybutynin and orphenadrine both decrease cholinergic effects/transmission. Use Caution/Monitor.oxcarbazepineMinor (1)oxcarbazepine will decrease the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.oxybutynin topicalMonitor Closely (1)oxybutynin and oxybutynin topical both decrease cholinergic effects/transmission. Use Caution/Monitor.oxybutynin transdermalMonitor Closely (1)oxybutynin and oxybutynin transdermal both decrease cholinergic effects/transmission. Use Caution/Monitor.paliperidoneMonitor Closely (3)oxybutynin decreases levels of paliperidone by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. oxybutynin decreases levels of paliperidone by pharmacodynamic antagonism. Use Caution/Monitor. paliperidone increases effects of oxybutynin by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.pancuroniumMonitor Closely (1)oxybutynin and pancuronium both decrease cholinergic effects/transmission. Use Caution/Monitor.pentobarbitalMinor (1)pentobarbital will decrease the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.perphenazineMonitor Closely (3)oxybutynin decreases levels of perphenazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. oxybutynin decreases levels of perphenazine by pharmacodynamic antagonism. Use Caution/Monitor. perphenazine increases effects of oxybutynin by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.Minor (1)oxybutynin increases toxicity of perphenazine by unspecified interaction mechanism. Minor/Significance Unknown.phenobarbitalMinor (1)phenobarbital will decrease the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.phenytoinMinor (1)phenytoin will decrease the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.physostigmineMonitor Closely (1)physostigmine increases and oxybutynin decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.pilocarpineMonitor Closely (1)pilocarpine increases and oxybutynin decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.pimozideMonitor Closely (3)oxybutynin decreases levels of pimozide by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. oxybutynin decreases levels of pimozide by pharmacodynamic antagonism. Use Caution/Monitor. pimozide increases effects of oxybutynin by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.posaconazoleMinor (1)posaconazole will increase the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.potassium chlorideSerious - Use Alternative (1)potassium chloride, oxybutynin. Other (see comment). Avoid or Use Alternate Drug. Comment: Patients using drugs with extensive anticholinergic effects should avoid concomitant use with solid oral dosage forms of potassium chloride. May use effervescent potassium preparations as alternatives. .pralidoximeMonitor Closely (1)oxybutynin and pralidoxime both decrease cholinergic effects/transmission. Use Caution/Monitor.pramlintideSerious - Use Alternative (1)pramlintide, oxybutynin. Either increases effects of the other by pharmacodynamic synergism. Contraindicated. Synergistic inhibition of GI motility.prednisoneMinor (1)prednisone will decrease the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.primidoneMinor (1)primidone will decrease the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.prochlorperazineMonitor Closely (3)oxybutynin decreases levels of prochlorperazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. oxybutynin decreases levels of prochlorperazine by pharmacodynamic antagonism. Use Caution/Monitor. prochlorperazine increases effects of oxybutynin by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.Minor (1)oxybutynin increases toxicity of prochlorperazine by unspecified interaction mechanism. Minor/Significance Unknown.promazineMinor (1)oxybutynin increases toxicity of promazine by unspecified interaction mechanism. Minor/Significance Unknown.promethazineMonitor Closely (3)oxybutynin decreases levels of promethazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. oxybutynin decreases levels of promethazine by pharmacodynamic antagonism. Use Caution/Monitor. promethazine increases effects of oxybutynin by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.Minor (1)oxybutynin increases toxicity of promethazine by unspecified interaction mechanism. Minor/Significance Unknown.propanthelineMonitor Closely (1)oxybutynin and propantheline both decrease cholinergic effects/transmission. Use Caution/Monitor.protriptylineMonitor Closely (1)oxybutynin and protriptyline both decrease cholinergic effects/transmission. Use Caution/Monitor.pyridostigmineMonitor Closely (1)pyridostigmine increases and oxybutynin decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.quetiapineMonitor Closely (3)oxybutynin decreases levels of quetiapine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. oxybutynin decreases levels of quetiapine by pharmacodynamic antagonism. Use Caution/Monitor. quetiapine increases effects of oxybutynin by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.quinupristin/dalfopristinMinor (1)quinupristin/dalfopristin will increase the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.rapacuroniumMonitor Closely (1)oxybutynin and rapacuronium both decrease cholinergic effects/transmission. Use Caution/Monitor.ribociclibMonitor Closely (1)ribociclib will increase the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.rifabutinMonitor Closely (1)rifabutin will decrease the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.rifampinMonitor Closely (1)rifampin will decrease the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.rifapentineMinor (1)rifapentine will decrease the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.rimantadineMonitor Closely (1)oxybutynin, rimantadine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Enhanced CNS side effects.risperidoneMonitor Closely (3)oxybutynin decreases levels of risperidone by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. oxybutynin decreases levels of risperidone by pharmacodynamic antagonism. Use Caution/Monitor. risperidone increases effects of oxybutynin by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.ritonavirMinor (1)ritonavir will increase the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.rivastigmineMonitor Closely (1)oxybutynin and rivastigmine both decrease cholinergic effects/transmission. Use Caution/Monitor.rocuroniumMonitor Closely (1)oxybutynin and rocuronium both decrease cholinergic effects/transmission. Use Caution/Monitor.ropeginterferon alfa 2bSerious - Use Alternative (1)ropeginterferon alfa 2b and oxybutynin both increase Other (see comment). Avoid or Use Alternate Drug. Narcotics, hypnotics or sedatives can produce additive neuropsychiatric side effects. Avoid use and monitor patients receiving the combination for effects of excessive CNS toxicity.rufinamideMinor (1)rufinamide will decrease the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.ruxolitinibMinor (1)oxybutynin will increase the level or effect of ruxolitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.ruxolitinib topicalMinor (1)oxybutynin will increase the level or effect of ruxolitinib topical by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.scopolamineMonitor Closely (1)oxybutynin and scopolamine both decrease cholinergic effects/transmission. Use Caution/Monitor.secobarbitalMinor (1)secobarbital will decrease the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.secretinSerious - Use Alternative (1)oxybutynin decreases effects of secretin by pharmacodynamic antagonism. Avoid or Use Alternate Drug. Concomitant use of anticholinergic drugs may cause a hyporesponse to stimulation testing with secretin. Discontinue anticholinergic drugs at least 5 half-lives before administering secretin.solifenacinMonitor Closely (1)oxybutynin and solifenacin both decrease cholinergic effects/transmission. Use Caution/Monitor.St John's WortMonitor Closely (1)St John's Wort will decrease the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.stiripentolMonitor Closely (1)stiripentol, oxybutynin. Either increases effects of the other by sedation. Use Caution/Monitor. Concomitant use stiripentol with other CNS depressants, including alcohol, may increase the risk of sedation and somnolence.succinylcholineMonitor Closely (1)succinylcholine increases and oxybutynin decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.tazemetostatMonitor Closely (1)oxybutynin will increase the level or effect of tazemetostat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.thioridazineMonitor Closely (3)oxybutynin decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. oxybutynin decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor. thioridazine increases effects of oxybutynin by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.Minor (1)oxybutynin increases toxicity of thioridazine by unspecified interaction mechanism. Minor/Significance Unknown.thiothixeneMonitor Closely (3)oxybutynin decreases levels of thiothixene by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. oxybutynin decreases levels of thiothixene by pharmacodynamic antagonism. Use Caution/Monitor. thiothixene increases effects of oxybutynin by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.tinidazoleMonitor Closely (1)oxybutynin will increase the level or effect of tinidazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.tiotropiumMonitor Closely (1)oxybutynin and tiotropium both decrease cholinergic effects/transmission. Use Caution/Monitor.tolterodineMonitor Closely (1)oxybutynin and tolterodine both decrease cholinergic effects/transmission. Use Caution/Monitor.topiramateMinor (1)topiramate will decrease the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.trazodoneMonitor Closely (1)oxybutynin and trazodone both decrease cholinergic effects/transmission. Use Caution/Monitor.trifluoperazineMonitor Closely (3)oxybutynin decreases levels of trifluoperazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. oxybutynin decreases levels of trifluoperazine by pharmacodynamic antagonism. Use Caution/Monitor. trifluoperazine increases effects of oxybutynin by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.Minor (1)oxybutynin increases toxicity of trifluoperazine by unspecified interaction mechanism. Minor/Significance Unknown.trihexyphenidylMonitor Closely (1)oxybutynin and trihexyphenidyl both decrease cholinergic effects/transmission. Use Caution/Monitor. Potential for additive anticholinergic effects.trimipramineMonitor Closely (1)oxybutynin and trimipramine both decrease cholinergic effects/transmission. Use Caution/Monitor.trospium chlorideMonitor Closely (1)oxybutynin and trospium chloride both decrease cholinergic effects/transmission. Use Caution/Monitor.vecuroniumMonitor Closely (1)oxybutynin and vecuronium both decrease cholinergic effects/transmission. Use Caution/Monitor.verapamilMinor (1)verapamil will increase the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.voriconazoleMinor (1)voriconazole will increase the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.zafirlukastMinor (1)zafirlukast will increase the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.ziprasidoneMonitor Closely (3)oxybutynin decreases levels of ziprasidone by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. oxybutynin decreases levels of ziprasidone by pharmacodynamic antagonism. Use Caution/Monitor. ziprasidone increases effects of oxybutynin by pharmacodynamic