and bisoprolol both increase anti-hypertensive channel blocking. Modify Therapy/Monitor Closely.brimonidineMinor (1)brimonidine increases effects of doxazosin by pharmacodynamic synergism. Minor/Significance Unknown.butcher's broomMinor (1)doxazosin, butcher's broom. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.captoprilMonitor Closely (1)captopril, doxazosin. Either increases effects of the other by Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Exaggerated first dose hypotensive response. Both drugs lower blood pressure. Monitor blood pressure.carbidopaMonitor Closely (1)carbidopa increases effects of doxazosin by pharmacodynamic synergism. Use Caution/Monitor. Therapy with carbidopa, given with or without levodopa or carbidopa-levodopa combination products, is started, dosage adjustment of the antihypertensive drug may be required.carvedilolMonitor Closely (1)doxazosin and carvedilol both increase anti-hypertensive channel blocking. Modify Therapy/Monitor Closely.celecoxibMonitor Closely (1)celecoxib decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.celiprololMonitor Closely (1)doxazosin and celiprolol both increase anti-hypertensive channel blocking. Modify Therapy/Monitor Closely.choline magnesium trisalicylateMonitor Closely (1)choline magnesium trisalicylate decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.clevidipineMonitor Closely (1)doxazosin and clevidipine both increase anti-hypertensive channel blocking. Use Caution/Monitor.clonidineMonitor Closely (1)clonidine, doxazosin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Additive sympatholytic action may worsen sinus node dysfunction and atrioventricular (AV) block.diclofenacMonitor Closely (1)diclofenac decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.diflunisalMonitor Closely (1)diflunisal decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.diltiazemMonitor Closely (1)doxazosin and diltiazem both increase anti-hypertensive channel blocking. Use Caution/Monitor.duvelisibMonitor Closely (1)duvelisib will increase the level or effect of doxazosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration with duvelisib increases AUC of a sensitive CYP3A4 substrate which may increase the risk of toxicities of these drugs. Consider reducing the dose of the sensitive CYP3A4 substrate and monitor for signs of toxicities of the coadministered sensitive CYP3A substrate.enalaprilMonitor Closely (1)enalapril, doxazosin. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Exaggerated first dose hypotensive response.esmololMonitor Closely (1)doxazosin and esmolol both increase anti-hypertensive channel blocking. Modify Therapy/Monitor Closely. The severity and duration of hypotension following the first dose of doxozosin may be enhanced.ethanolMinor (1)doxazosin, ethanol. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Risk of hypotension, esp. in Asian pts.etodolacMonitor Closely (1)etodolac decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.felodipineMonitor Closely (1)doxazosin and felodipine both increase anti-hypertensive channel blocking. Use Caution/Monitor.fenoprofenMonitor Closely (1)fenoprofen decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.flurbiprofenMonitor Closely (1)flurbiprofen decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.fosinoprilMonitor Closely (1)fosinopril, doxazosin. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Exaggerated first dose hypotensive response.ibuprofenMonitor Closely (1)ibuprofen decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.ibuprofen IVMonitor Closely (1)ibuprofen IV decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.iloperidoneMonitor Closely (1)iloperidone increases effects of doxazosin by pharmacodynamic synergism. Use Caution/Monitor.imidaprilMonitor Closely (1)imidapril, doxazosin. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Exaggerated first dose hypotensive response.indomethacinMonitor Closely (1)indomethacin decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.isradipineMonitor Closely (1)doxazosin and isradipine both increase anti-hypertensive channel blocking. Use Caution/Monitor.ketoprofenMonitor Closely (1)ketoprofen decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.ketorolacMonitor Closely (1)ketorolac decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.ketorolac intranasalMonitor Closely (1)ketorolac intranasal decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.labetalolMonitor Closely (1)doxazosin and labetalol both increase anti-hypertensive channel blocking. Modify Therapy/Monitor Closely.levodopaMonitor Closely (1)levodopa increases effects of doxazosin by pharmacodynamic synergism. Use Caution/Monitor. Consider decreasing dosage of antihypertensive agent.lisinoprilMonitor Closely (1)lisinopril, doxazosin. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Exaggerated first dose hypotensive response.lornoxicamMonitor Closely (1)lornoxicam decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.lurasidoneMonitor Closely (1)lurasidone increases effects of doxazosin 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.maravirocMonitor Closely (1)maraviroc, doxazosin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of orthostatic hypotension.meclofenamateMonitor Closely (1)meclofenamate decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.mefenamic acidMonitor Closely (1)mefenamic acid decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.meloxicamMonitor Closely (1)meloxicam decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.metoprololMonitor Closely (1)doxazosin and metoprolol both increase anti-hypertensive channel blocking. Modify Therapy/Monitor Closely.moexiprilMonitor Closely (1)moexipril, doxazosin. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Exaggerated first dose hypotensive response.moxisylyteMonitor Closely (1)doxazosin and moxisylyte both increase anti-hypertensive channel blocking. Use Caution/Monitor.nabumetoneMonitor Closely (1)nabumetone decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.nadololMonitor Closely (1)doxazosin and nadolol both increase anti-hypertensive channel blocking. Modify Therapy/Monitor Closely.naproxenMonitor Closely (1)naproxen decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.nebivololMonitor Closely (1)doxazosin and nebivolol both increase anti-hypertensive channel blocking. Modify Therapy/Monitor Closely.nicardipineMonitor Closely (1)doxazosin and nicardipine both increase anti-hypertensive channel blocking. Use Caution/Monitor.nifedipineMonitor Closely (1)doxazosin and nifedipine both increase anti-hypertensive channel blocking. Use Caution/Monitor.nirmatrelvir/ritonavirMonitor Closely (1)nirmatrelvir/ritonavir will increase the level or effect of doxazosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Monitor for increased bradycardia, hypotension, or dizziness. If needed, temporarily pause the antihypertensive drug. nisoldipineMonitor Closely (1)doxazosin and nisoldipine both increase anti-hypertensive channel blocking. Use Caution/Monitor.nitroglycerin rectalMonitor Closely (1)nitroglycerin rectal, doxazosin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Observe for possible additive hypotensive effects during concomitant use. .oxaprozinMonitor Closely (1)oxaprozin decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.oxymetazoline topicalMonitor Closely (1)oxymetazoline topical increases and doxazosin decreases sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Effect of interaction is not clear, use caution. Use Caution/Monitor.parecoxibMonitor Closely (1)parecoxib decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.penbutololMonitor Closely (1)doxazosin and penbutolol both increase anti-hypertensive channel blocking. Modify Therapy/Monitor Closely.perindoprilMonitor Closely (1)perindopril, doxazosin. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Exaggerated first dose hypotensive response.phenoxybenzamineMonitor Closely (1)doxazosin and phenoxybenzamine both increase anti-hypertensive channel blocking. Use Caution/Monitor.phentolamineMonitor Closely (1)doxazosin and phentolamine both increase anti-hypertensive channel blocking. Use Caution/Monitor.phenylephrineMinor (1)doxazosin, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.phenylephrine POMinor (1)doxazosin, phenylephrine PO. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.pindololMonitor Closely (1)doxazosin and pindolol both increase anti-hypertensive channel blocking. Modify Therapy/Monitor Closely.piroxicamMonitor Closely (1)piroxicam decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.prazosinMonitor Closely (1)doxazosin and prazosin both increase anti-hypertensive channel blocking. Use Caution/Monitor.propranololMonitor Closely (1)doxazosin and propranolol both increase anti-hypertensive channel blocking. Modify Therapy/Monitor Closely. The severity and duration of hypotension following the first dose of doxozosin may be enhanced.pseudoephedrineMonitor Closely (1)pseudoephedrine decreases effects of doxazosin by sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.quinaprilMonitor Closely (1)quinapril, doxazosin. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Exaggerated first dose hypotensive response.ramiprilMonitor Closely (1)ramipril, doxazosin. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Exaggerated first dose hypotensive response.salicylates (non-asa)Monitor Closely (1)salicylates (non-asa) decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.salsalateMonitor Closely (1)salsalate decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.sildenafilSerious - Use Alternative (1)sildenafil increases effects of doxazosin by pharmacodynamic synergism. Avoid or Use Alternate Drug. Risk of hypotension; separate sildenafil >25mg from alpha blocker by 4hr.silodosinMonitor Closely (1)doxazosin and silodosin both increase anti-hypertensive channel blocking. Use Caution/Monitor.sotalolMonitor Closely (1)doxazosin and sotalol both increase anti-hypertensive channel blocking. Modify Therapy/Monitor Closely. The severity and duration of hypotension following the first dose of doxozosin may be enhanced.sulfasalazineMonitor Closely (1)sulfasalazine decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.sulindacMonitor Closely (1)sulindac decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.tadalafilMonitor Closely (1)tadalafil increases effects of doxazosin by pharmacodynamic synergism. Use Caution/Monitor. Risk of hypotension.tamsulosinSerious - Use Alternative (1)doxazosin, tamsulosin. Either increases effects of the other by additive vasodilation. Avoid or Use Alternate Drug. Risk of hypotension.terazosinMonitor Closely (1)doxazosin and terazosin both increase anti-hypertensive channel blocking. Use Caution/Monitor.timololMonitor Closely (1)doxazosin and timolol both increase anti-hypertensive channel blocking. Modify Therapy/Monitor Closely.tizanidineMinor (1)tizanidine increases effects of doxazosin by pharmacodynamic synergism. Minor/Significance Unknown. Risk of hypotension.tolfenamic acidMonitor Closely (1)tolfenamic acid decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.tolmetinMonitor Closely (1)tolmetin decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.trandolaprilMonitor Closely (1)trandolapril, doxazosin. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Exaggerated first dose hypotensive response.treprostinilMinor (1)treprostinil increases effects of doxazosin by pharmacodynamic synergism. Minor/Significance Unknown.vardenafilSerious - Use Alternative (1)vardenafil increases effects of doxazosin by pharmacodynamic synergism. Contraindicated. Risk of hypotension.verapamilMonitor Closely (1)doxazosin and verapamil both increase anti-hypertensive channel blocking. Use Caution/Monitor.yohimbeSerious - Use Alternative (1)yohimbe increases effects of doxazosin by pharmacodynamic synergism. Contraindicated.zotepineMonitor Closely (1)doxazosin and zotepine both increase anti-hypertensive channel blocking. Use Caution/Monitor. >10% Dizziness (5-19%) Fatigue (8-12%) Headache (6-10%) 1-10% Vertigo (7%) Upper respiratory tract infection (URTI) (5%) Edema (3-4%) Rhinitis (3%) Dyspnea (1-3%) Abdominal pain (2%) Hypotension (1-2%) Nausea (1-2%) Orthostatic hypotension (dose related) (0.3-2%) Anxiety (1%) Palpitations (1%) Postmarketing experience Autonomic Nervous System: Priapism Cardiovascular System: Cerebrovascular accidents, dizziness postural, myocardial infarction Central and Peripheral Nervous System: Hypoesthesia, paresthesia Endocrine System: Gynecomastia Gastrointestinal System: Gastrointestinal obstruction, vomiting General Body System: Fatigue, hot flushes, malaise Heart Rate/Rhythm: Bradycardia, cardiac arrhythmias Hematopoietic: Leukopenia, purpura, thrombocytopenia Liver/Biliary System: Abnormal liver function tests, hepatitis, hepatitis cholestatic, jaundice Musculoskeletal System: Muscle cramps, muscle weakness Psychiatric: Agitation, anorexia, nervousness Respiratory System: Bronchospasm aggravated Skin Disorders: Alopecia, urticaria, skin rash, pruritus Special Senses: Blurred vision, intraoperative Floppy Iris Syndrome Urinary System: Hematuria, micturition disorder, micturition frequency, nocturia, polyuria Contraindications Hypersensitivity to doxazosin or other quinazolines Cautions Use with caution in liver disease or recent cerebrovascular accident (CVA) Rule out prostate cancer before initiating therapy May cause first-dose syncope or sudden loss of consciousness Risk of orthostatic hypotension (dose dependent) Potential for hypotension, dry mouth, and urinary complications in elderly Priapism (painful penile erection, sustained for hours and unrelieved by sexual intercourse or masturbation) rarely reported (probably less frequently than once in every several thousand patients), with alpha-1 antagonists, including doxazosin; because condition can lead to permanent impotence if not promptly treated, patients must be advised about seriousness of condition Concomitant use of other antihypertensives (additive hypotensive effects) Extended-release form not indicated for hypertension Concomitant administration of immediate-release form with a phosphodiesterase-5 (PDE-5) inhibitor can result in additive blood pressure lowering effects and symptomatic hypotension May increase the risk of heart failure by exacerbating underlying myocardial dysfunction by β1Receptor stimulation with increases in renin and aldosterone May cause CNS depression, which may impair ability to operate heavy machinery and performing tasks that require mental alertness Allergic reactions, including urticaria, rash, angioedema, pruritus, and respiratory symptoms may occur Intraoperative floppy iris syndrome reported in cataract surgery patients who received alph1-blocker therapy; discontinuing alpha-blocker therapy prior to surgery does not appear to be of benefit Decreases in white blood cells (WBC) and neutrophil count reported; WBC and neutrophil counts returned to normal following discontinuation of therapy Pregnancy Not indicated for use in females or for the treatment of hypertension; the limited available data in pregnant women are not sufficient to inform a drug-associated risk for major birth defects and miscarriage; no adverse developmental outcomes were observed in animal reproduction studies with oral administration to pregnant rats and rabbits at doses of up to 10 and 4 times, respectively, the 12 mg/day recommended dose; postnatal development was delayed in rats at a dose of 8 times the 12 mg/day recommended dose Lactation Present in human milk; there is no information on effects on breastfed infant or effects on milk productionPregnancy Categories A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk. B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk. C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done. D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk. X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist. NA: Information not available. Mechanism of Action Hypertension: Blocks postsynaptic alpha1 receptors; alpha blockade causes arterial, arteriolar, and venous dilation; decreases total peripheral resistance and blood pressure Benign prostatic hyperplasia (BPH): Blocks alpha1 receptors in prostatic stromal and bladder tissues; reduces sympathetic tone-induced urethral stricture responsible for BPH symptoms