effects of guanfacine by pharmacodynamic synergism. Use Caution/Monitor. Consider decreasing dosage of antihypertensive agent.levoketoconazoleMonitor Closely (1)levoketoconazole will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available. lofepramineSerious - Use Alternative (1)lofepramine decreases effects of guanfacine by Other (see comment). Avoid or Use Alternate Drug. Comment: Inhibition of uptake by adrenergic neurons.lofexidineSerious - Use Alternative (1)lofexidine, guanfacine. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Avoid coadministration with other drugs that decrease pulse or blood pressure to mitigate risk of excessive bradycardia and hypotension.lopinavirMonitor Closely (1)lopinavir will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.lorlatinibSerious - Use Alternative (1)lorlatinib will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.loxapineMonitor Closely (1)guanfacine, loxapine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.loxapine inhaledMonitor Closely (1)guanfacine, loxapine inhaled. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.lumacaftor/ivacaftorMonitor Closely (1)lumacaftor/ivacaftor will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.lurasidoneMonitor Closely (2)lurasidone, guanfacine. Either increases toxicity of the other by sedation. Use Caution/Monitor. Potential for increased CNS depressant effects when used concurrently; monitor for increased adverse effects and toxicity. lurasidone increases effects of guanfacine by Other (see comment). Use Caution/Monitor. Comment: Potential for increased risk of hypotension with concurrent use. Monitor blood pressure and adjust dose of antihypertensive agent as needed.maitakeMinor (1)maitake increases effects of guanfacine by pharmacodynamic synergism. Minor/Significance Unknown.maprotilineSerious - Use Alternative (1)maprotiline decreases effects of guanfacine by Other (see comment). Avoid or Use Alternate Drug. Comment: Inhibition of uptake by adrenergic neurons.metforminMinor (2)guanfacine decreases effects of metformin by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia. guanfacine, metformin. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.metoclopramide intranasalSerious - Use Alternative (1)guanfacine, 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.metoprololMinor (1)metoprolol, guanfacine. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Selective beta blocker administration during withdrawal from centrally acting alpha agonists may result in rebound hypertension.metronidazoleMonitor Closely (1)metronidazole will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available. midazolam intranasalMonitor Closely (1)midazolam intranasal, guanfacine. 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.mifepristoneSerious - Use Alternative (1)mifepristone will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.miglitolMinor (2)guanfacine decreases effects of miglitol by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia. guanfacine, miglitol. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.mirtazapineSerious - Use Alternative (1)mirtazapine decreases effects of guanfacine by pharmacodynamic antagonism. Avoid or Use Alternate Drug. Risk of hypertensive urgency.mitotaneMonitor Closely (1)mitotane decreases levels of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.nadololMonitor Closely (1)nadolol, guanfacine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Non selective beta blocker administration during withdrawal from centrally acting alpha agonists may result in rebound hypertension.nafcillinMonitor Closely (1)nafcillin will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.nateglinideMinor (2)guanfacine decreases effects of nateglinide by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia. guanfacine, nateglinide. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.nebivololMinor (1)nebivolol, guanfacine. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Selective beta blocker administration during withdrawal from centrally acting alpha agonists may result in rebound hypertension.nefazodoneMonitor Closely (1)nefazodone will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available. nelfinavirMonitor Closely (1)nelfinavir will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available. netupitant/palonosetronMonitor Closely (1)netupitant/palonosetron will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.nevirapineMonitor Closely (1)nevirapine will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.nicardipineMonitor Closely (1)nicardipine will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.nilotinibMonitor Closely (1)nilotinib will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.nitroglycerin rectalMonitor Closely (1)nitroglycerin rectal, guanfacine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Observe for possible additive hypotensive effects during concomitant use. .nitroprusside sodiumMonitor Closely (1)nitroprusside sodium, guanfacine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects.nortriptylineSerious - Use Alternative (1)nortriptyline decreases effects of guanfacine by Other (see comment). Avoid or Use Alternate Drug. Comment: Inhibition of uptake by adrenergic neurons.octacosanolMinor (1)octacosanol increases effects of guanfacine by pharmacodynamic synergism. Minor/Significance Unknown.olanzapineMonitor Closely (1)guanfacine, olanzapine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.olopatadine intranasalSerious - Use Alternative (1)guanfacine 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. oxcarbazepineMonitor Closely (1)oxcarbazepine will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.paliperidoneMonitor Closely (1)guanfacine, paliperidone. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.penbutololMinor (1)penbutolol, guanfacine. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Selective beta blocker administration during withdrawal from centrally acting alpha agonists may result in rebound hypertension.pentobarbitalMonitor Closely (1)pentobarbital will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.perphenazineMonitor Closely (1)guanfacine, perphenazine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.phenobarbitalMonitor Closely (1)phenobarbital will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.phenytoinMonitor Closely (1)phenytoin will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.pimozideMonitor Closely (1)guanfacine, pimozide. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.pindololMonitor Closely (1)pindolol, guanfacine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Non selective beta blocker administration during withdrawal from centrally acting alpha agonists may result in rebound hypertension.pioglitazoneMinor (2)guanfacine decreases effects of pioglitazone by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia. guanfacine, pioglitazone. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.ponesimodSerious - Use Alternative (1)ponesimod, guanfacine. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Consult cardiologist if considering treatment. Coadministration of ponesimod with drugs that decrease HR may have additive effects on decreasing HR and should generally not be initiated in these patients.posaconazoleMonitor Closely (1)posaconazole will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available. primidoneMonitor Closely (1)primidone will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.prochlorperazineMonitor Closely (1)guanfacine, prochlorperazine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.promethazineMonitor Closely (1)guanfacine, promethazine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.propranololMonitor Closely (1)propranolol, guanfacine. Mechanism: