increases effects of oxybutynin by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia. oxybutynin and amitriptyline both decrease cholinergic effects/transmission. Use Caution/Monitor.Minor (1)oxybutynin increases toxicity of perphenazine by unspecified interaction mechanism. Minor/Significance Unknown.oxybutynin topicalMonitor Closely (4)oxybutynin topical decreases levels of perphenazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. perphenazine increases effects of oxybutynin topical by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia. oxybutynin topical and amitriptyline both decrease cholinergic effects/transmission. Use Caution/Monitor. oxybutynin topical decreases levels of perphenazine by pharmacodynamic antagonism. Use Caution/Monitor.Minor (1)oxybutynin topical increases toxicity of perphenazine by unspecified interaction mechanism. Minor/Significance Unknown.oxybutynin transdermalMonitor Closely (4)oxybutynin transdermal decreases levels of perphenazine by pharmacodynamic antagonism. Use Caution/Monitor. oxybutynin transdermal decreases levels of perphenazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. perphenazine increases effects of oxybutynin transdermal by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia. oxybutynin transdermal and amitriptyline both decrease cholinergic effects/transmission. Use Caution/Monitor.Minor (1)oxybutynin transdermal increases toxicity of perphenazine by unspecified interaction mechanism. Minor/Significance Unknown.oxycodoneMonitor Closely (3)oxycodone and perphenazine both increase sedation. Use Caution/Monitor. perphenazine will increase the level or effect of oxycodone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. oxycodone and amitriptyline both increase sedation. Use Caution/Monitor.Minor (1)perphenazine decreases effects of oxycodone by decreasing metabolism. Minor/Significance Unknown. Decreased conversion of oxycodone to active metabolite morphine.oxymetazoline intranasalMonitor Closely (1)amitriptyline increases effects of oxymetazoline intranasal by pharmacodynamic synergism. Use Caution/Monitor. TCAs inhibit norepinephrine uptake in adrenergic neurons, thereby increasing synaptic norepinephrine levels. Coadministration with alpha1 agonists may cause increased adrenergic receptor stimulation. When oxymetazoline is combined with intranasal tetracaine for dental anesthesia, avoid or use alternant anesthetic in patients taking TCAs.oxymorphoneMonitor Closely (3)oxymorphone and amitriptyline both increase sedation. Use Caution/Monitor. perphenazine will increase the level or effect of oxymorphone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. oxymorphone and perphenazine both increase sedation. Use Caution/Monitor.ozanimodMonitor Closely (2)ozanimod and perphenazine both increase QTc interval. Modify Therapy/Monitor Closely. The potential additive effects on heart rate, treatment with ozanimod should generally not be initiated in patients who are concurrently treated with QT prolonging drugs with known arrhythmogenic properties. ozanimod and amitriptyline both increase QTc interval. Modify Therapy/Monitor Closely. The potential additive effects on heart rate, treatment with ozanimod should generally not be initiated in patients who are concurrently treated with QT prolonging drugs with known arrhythmogenic properties.Serious - Use Alternative (1)ozanimod increases toxicity of amitriptyline by sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Avoid or Use Alternate Drug. Because the active metabolite of ozanimod inhibits MAO-B in vitro, there is a potential for serious adverse reactions, including hypertensive crisis. Therefore, coadministration of ozanimod with drugs that can increase norepinephrine or serotonin is not recommended. Monitor for hypertension with concomitant use.paliperidoneMonitor Closely (5)amitriptyline and paliperidone both increase QTc interval. Modify Therapy/Monitor Closely. paliperidone and perphenazine both increase sedation. Use Caution/Monitor. paliperidone and perphenazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor. paliperidone and amitriptyline both increase sedation. Use Caution/Monitor. perphenazine and paliperidone both increase QTc interval. Modify Therapy/Monitor Closely.palonosetronSerious - Use Alternative (1)palonosetron, amitriptyline. Either increases toxicity of the other by serotonin levels. Avoid or Use Alternate Drug.panax ginsengMinor (1)panax ginseng increases effects of amitriptyline by pharmacodynamic synergism. Minor/Significance Unknown.pancuroniumMonitor Closely (4)pancuronium and amitriptyline both decrease cholinergic effects/transmission. Use Caution/Monitor. perphenazine increases effects of pancuronium by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia. pancuronium decreases levels of perphenazine by pharmacodynamic antagonism. Use Caution/Monitor. pancuronium decreases levels of perphenazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.panobinostatMonitor Closely (1)panobinostat will increase the level or effect of perphenazine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Panobinostat can increase the levels and effects of sensitive CYP2D6 substrates or those with a narrow therapeutic index CYP2D6.papaveretumMonitor Closely (2)papaveretum and perphenazine both increase sedation. Use Caution/Monitor. papaveretum and amitriptyline both increase sedation. Use Caution/Monitor.papaverineMonitor Closely (2)perphenazine and papaverine both increase sedation. Use Caution/Monitor. amitriptyline and papaverine both increase sedation. Use Caution/Monitor.parecoxibMinor (2)parecoxib will increase the level or effect of perphenazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown. parecoxib will increase the level or effect of amitriptyline by affecting hepatic enzyme CYP2C19 metabolism. Minor/Significance Unknown.paroxetineMonitor Closely (2)paroxetine, perphenazine. 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). amitriptyline and paroxetine both increase QTc interval. Modify Therapy/Monitor Closely.Serious - Use Alternative (4)paroxetine will increase the level or effect of perphenazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. perphenazine will increase the level or effect of paroxetine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. perphenazine and paroxetine both increase QTc interval. Avoid or Use Alternate Drug. paroxetine and amitriptyline both increase serotonin levels. Avoid or Use Alternate Drug.pasireotideMonitor Closely (2)amitriptyline and pasireotide both increase QTc interval. Modify Therapy/Monitor Closely. perphenazine and pasireotide both increase QTc interval. Modify Therapy/Monitor Closely.pazopanibMonitor Closely (2)perphenazine and pazopanib both increase QTc interval. Use Caution/Monitor. amitriptyline and pazopanib both increase QTc interval. Use Caution/Monitor.peginterferon alfa 2bMonitor Closely (2)peginterferon alfa 2b, perphenazine. Other (see comment). Use Caution/Monitor. Comment: When patients are administered peginterferon alpha-2b with CYP2D6 substrates, the therapeutic effect of these drugs may be altered. Peginterferon alpha-2b may increase or decrease levels of CYP2D6 substrate. peginterferon alfa 2b, amitriptyline. Other (see comment). Use Caution/Monitor. Comment: When patients are administered peginterferon alpha-2b with CYP2D6 substrates, the therapeutic effect of these drugs may be altered. Peginterferon alpha-2b may increase or decrease levels of CYP2D6 substrate.pentamidineContraindicated (2)perphenazine and pentamidine both increase QTc interval. Contraindicated. amitriptyline and pentamidine both increase QTc interval. Contraindicated.pentazocineMonitor Closely (3)amitriptyline and pentazocine both increase serotonin levels. Modify Therapy/Monitor Closely. pentazocine and perphenazine both increase sedation. Use Caution/Monitor. pentazocine and amitriptyline both increase sedation. Use Caution/Monitor.pentobarbitalMonitor Closely (4)pentobarbital and perphenazine both increase sedation. Use Caution/Monitor. pentobarbital will decrease the level or effect of amitriptyline by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. pentobarbital will decrease the level or effect of amitriptyline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. pentobarbital and amitriptyline both increase sedation. Use Caution/Monitor.Minor (1)pentobarbital, amitriptyline. Other (see comment). Minor/Significance Unknown. Comment: Barbiturates may increase adverse effects, including respiratory depression, produced by toxic doses of TCAs. With therapeutic doses of TCAs, barbiturates increase metabolism and decrease blood concentrations of TCAs.perhexilineMinor (1)perphenazine will increase the level or effect of perhexiline by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.perindoprilMinor (1)perphenazine increases effects of perindopril by unspecified interaction mechanism. Minor/Significance Unknown.perphenazineMonitor Closely (1)perphenazine and amitriptyline both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)perphenazine and amitriptyline both increase QTc interval. Avoid or Use Alternate Drug.Minor (2)amitriptyline, perphenazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects. amitriptyline, perphenazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.phendimetrazineMonitor Closely (3)perphenazine, phendimetrazine. 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. perphenazine increases and phendimetrazine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. amitriptyline increases and phendimetrazine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Serious - Use Alternative (1)amitriptyline, phendimetrazine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.phenelzineContraindicated (1)phenelzine and amitriptyline both increase serotonin levels. Contraindicated.Monitor Closely (1)phenelzine, perphenazine. 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).phenobarbitalMonitor Closely (5)phenobarbital will decrease the level or effect of amitriptyline by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. phenobarbital will decrease the level or effect of amitriptyline by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. phenobarbital will decrease the level or effect of amitriptyline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. phenobarbital and perphenazine both increase sedation. Use Caution/Monitor. phenobarbital and amitriptyline both increase sedation. Use Caution/Monitor.Minor (1)phenobarbital, amitriptyline. Other (see comment). Minor/Significance Unknown. Comment: Barbiturates may increase adverse effects, including respiratory depression, produced by toxic doses of TCAs. With therapeutic doses of TCAs, barbiturates increase metabolism and decrease blood concentrations of TCAs.phentermineMonitor Closely (3)perphenazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. amitriptyline increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. perphenazine, phentermine. 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.Serious - Use Alternative (1)amitriptyline, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.phenylephrineMonitor Closely (3)perphenazine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. amitriptyline increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. perphenazine, phenylephrine. 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.Serious - Use Alternative (1)amitriptyline, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.phenylephrine ophthalmicMonitor Closely (1)amitriptyline, phenylephrine ophthalmic. Other (see comment). Use Caution/Monitor. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.phenylephrine POMonitor Closely (1)amitriptyline increases and phenylephrine PO decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. .Serious - Use Alternative (1)amitriptyline, phenylephrine PO. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.phenytoinMonitor Closely (2)phenytoin will decrease the level or effect of amitriptyline by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Monitor therapeutic efficacy of amitriptyline; an increased dose may be required. Serum phenytoin levels should be obtained when tricyclic antidepressant agents are added to therapy due to the potential for impaired phenytoin metabolism and decreased seizure threshold. Tricyclic antidepressants when given concomitantly with anticonvulsants can increase CNS depression. phenytoin will decrease the level or effect of amitriptyline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Monitor therapeutic efficacy of amitriptyline; an increased dose may be required. Serum phenytoin levels should be obtained when tricyclic antidepressant agents are added to therapy due to the potential for impaired phenytoin metabolism and decreased seizure threshold. Tricyclic antidepressants when given concomitantly with anticonvulsants can increase CNS depression.pholcodineMonitor Closely (2)perphenazine and pholcodine both increase sedation. Use Caution/Monitor. amitriptyline and pholcodine both increase sedation. Use Caution/Monitor.physostigmineMonitor Closely (1)physostigmine increases and amitriptyline decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.pilocarpineMonitor Closely (1)pilocarpine increases and amitriptyline decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.pimozideContraindicated (2)perphenazine and pimozide both increase QTc interval. Contraindicated. amitriptyline and pimozide both increase QTc interval. Contraindicated.Monitor Closely (3)perphenazine and pimozide both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor. pimozide and amitriptyline both increase sedation. Use Caution/Monitor. perphenazine and pimozide both increase sedation. Use Caution/Monitor.pioglitazoneMinor (1)amitriptyline increases effects of pioglitazone by pharmacodynamic synergism. Minor/Significance Unknown.pirbuterolMonitor Closely (2)amitriptyline increases and pirbuterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. perphenazine increases and pirbuterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Serious - Use Alternative (1)amitriptyline, pirbuterol. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic