Doxazosin mesylate

6 ADVERSE REACTIONS The most commonly reported adverse reactions from clinical trials are Fatigue, malaise, hypotension, and dizziness. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Chartwell RX, LLC. at 1-845-232-1683 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

4 CONTRAINDICATIONS The use of doxazosin mesylate is contraindicated in patients with a hypersensitivity to doxazosin, other quinazolines (e.g., prazosin, terazosin), or any of its components. Hypersensitivity to doxazosin, other quinazolines, or any other ingredient in doxazosin mesylate tablets. ( 4 )

11 DESCRIPTION Doxazosin mesylate is a quinazoline compound that is a selective inhibitor of the alpha 1 subtype of alpha-adrenergic receptors. The chemical name of doxazosin mesylate is 1-(4-amino-6,7-dimethoxy-2-quinazolinyl)-4-(1,4-benzodioxan-2-ylcarbonyl) piperazine methanesulfonate. The empirical formula for doxazosin mesylate is C 23 H 25 N 5 O 5 · CH 4 O 3 S and the molecular weight is 547.6. It has the following structure: Doxazosin mesylate is freely soluble in dimethylsulfoxide, soluble in dimethylformamide, slightly soluble in methanol, ethanol, and water (0.8% at 25°C), and very slightly soluble in acetone and methylene chloride. Doxazosin mesylate is available as colored tablets for oral use and contains doxazosin mesylate equivalent to 1 mg, 2 mg, 4 mg, and 8 mg of doxazosin as the free base. The inactive ingredients for all tablets are lactose monohydrate, microcrystalline cellulose, sodium lauryl sulfate, sodium starch glycolate, and magnesium stearate. "Image Description"

2 DOSAGE AND ADMINISTRATION For the treatment of BPH: Initiate therapy at 1 mg once daily. Dose may be titrated at 1 to 2-week intervals, up to 8 mg once daily. ( 2.2 ) For the treatment hypertension: Initiate therapy at 1 mg once daily. Dose may be titrated as needed, up to 16 mg once daily. ( 2.3 )

1 INDICATIONS AND USAGE Doxazosin mesylate tablets are an alpha 1 adrenergic antagonist indicated for: ( 1 ) Signs and symptoms of Benign Prostatic Hyperplasia (BPH) Treatment of Hypertension

10 OVERDOSAGE Experience with doxazosin mesylate overdosage is limited. Two adolescents, who each intentionally ingested 40 mg doxazosin mesylate with diclofenac or acetaminophen, were treated with gastric lavage with activated charcoal and made full recoveries. A two-year-old child who accidently ingested 4 mg doxazosin mesylate was treated with gastric lavage and remained normotensive during the five-hour emergency room observation period. A six-month-old child accidentally received a crushed 1 mg tablet of doxazosin mesylate and was reported to have been drowsy. A 32-year-old female with chronic renal failure, epilepsy, and depression intentionally ingested 60 mg doxazosin mesylate (blood level = 0.9 mcg/mL; normal values in hypertensives = 0.02 mcg/mL); death was attributed to a grand mal seizure resulting from hypotension. A 39-year-old female who ingested 70 mg doxazosin mesylate, alcohol, and Dalmane ® (flurazepam) developed hypotension which responded to fluid therapy. The oral LD 50 of doxazosin is greater than 1000 mg/kg in mice and rats. The most likely manifestation of overdosage would be hypotension, for which the usual treatment would be intravenous infusion of fluid. As doxazosin is highly protein bound, dialysis would not be indicated.

7 DRUG INTERACTIONS Strong cytochrome P450 (CYP) 3A inhibitors may increase exposure to doxazosin and increased risk of hypotension. ( 7.1 ) Concomitant administration of doxazosin mesylate with a phosphodiesterase-5 (PDE-5) inhibitor can result in additive blood pressure lowering effects and symptomatic hypotension. ( 7.2 )

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action Benign Prostatic Hyperplasia (BPH) The symptoms associated with benign prostatic hyperplasia (BPH), such as urinary frequency, nocturia, weak stream, hesitancy, and incomplete emptying are related to two components, anatomical (static) and functional (dynamic). The static component is related to an increase in prostate size caused, in part, by a proliferation of smooth muscle cells in the prostatic stroma. However, the severity of BPH symptoms and the degree of urethral obstruction do not correlate well with the size of the prostate. The dynamic component of BPH is associated with an increase in smooth muscle tone in the prostate and bladder neck. The degree of tone in this area is mediated by the alpha 1 adrenoceptor, which is present in high density in the prostatic stroma, prostatic capsule and bladder neck. Blockade of the alpha 1 receptor decreases urethral resistance and may relieve the obstruction and BPH symptoms and improve urine flow. Hypertension The mechanism of action of doxazosin mesylate is selective blockade of the alpha 1 (postjunctional) subtype of adrenergic receptors. Studies in normal human subjects have shown that doxazosin competitively antagonized the pressor effects of phenylephrine (an alpha 1 agonist) and the systolic pressor effect of norepinephrine. Doxazosin and prazosin have similar abilities to antagonize phenylephrine. The antihypertensive effect of doxazosin mesylate results from a decrease in systemic vascular resistance. The parent compound doxazosin is primarily responsible for the antihypertensive activity. The low plasma concentrations of known active and inactive metabolites of doxazosin (2-piperazinyl, 6'- and 7'-hydroxy and 6- and 7-O-desmethyl compounds) compared to parent drug indicate that the contribution of even the most potent compound (6'-hydroxy) to the antihypertensive effect of doxazosin in man is probably small. The 6'- and 7'-hydroxy metabolites have demonstrated antioxidant properties at concentrations of 5 µM, in vitro .

12.2 Pharmacodynamics Benign Prostatic Hyperplasia (BPH) Administration of doxazosin mesylate to patients with symptomatic BPH resulted in a statistically significant improvement in maximum urinary flow rate [ see Clinical Studies (14.1) ]. Effect on Normotensive Patients with Benign Prostatic Hyperplasia (BPH) Although blockade of alpha 1 adrenoceptors also lowers blood pressure in hypertensive patients with increased peripheral vascular resistance, doxazosin mesylate treatment of normotensive men with BPH did not result in a clinically significant blood pressure lowering effect (Table 4). The proportion of normotensive patients with a sitting systolic blood pressure less than 90 mmHg and/or diastolic blood pressure less than 60 mmHg at any time during treatment with doxazosin mesylate 1–8 mg once daily was 6.7% with doxazosin and not significantly different (statistically) from that with placebo (5%). Hypertension Administration of doxazosin mesylate results in a reduction in systemic vascular resistance. In patients with hypertension, there is little change in cardiac output. Maximum reductions in blood pressure usually occur 2–6 hours after dosing and are associated with a small increase in standing heart rate. Like other alpha 1 -adrenergic blocking agents, doxazosin has a greater effect on blood pressure and heart rate in the standing position.

12.3 Pharmacokinetics Absorption After oral administration of therapeutic doses, peak plasma levels of doxazosin mesylate occur at about 2–3 hours. Bioavailability is approximately 65%, reflecting first-pass metabolism of doxazosin by the liver. The effect of food on the pharmacokinetics of doxazosin mesylate was examined in a crossover study with twelve hypertensive subjects. Reductions of 18% in mean maximum plasma concentration (C max ) and 12% in the area under the concentration-time curve (AUC) occurred when doxazosin mesylate was administered with food. Neither of these differences is clinically significant. In a crossover study in 24 normotensive subjects, the pharmacokinetics and safety of doxazosin were shown to be similar with morning and evening dosing regimens. The AUC after morning dosing was, however, 11% less than that after evening dosing and the time to peak concentration after evening dosing occurred significantly later than that after morning dosing (5.6 vs. 3.5 hours). Distribution At the plasma concentrations achieved by therapeutic doses, approximately 98% of the circulating drug is bound to plasma proteins. Metabolism Doxazosin mesylate is extensively metabolized in the liver, mainly by O-demethylation of the quinazoline nucleus or hydroxylation of the benzodioxan moiety. In vitro studies suggest that the primary pathway for elimination is via CYP 3A4; however, CYP 2D6 and CYP 2C9 metabolic pathways are also involved to a lesser extent. Although several active metabolites of doxazosin have been identified, the pharmacokinetics of these metabolites have not been characterized. Excretion Plasma elimination of doxazosin is biphasic, with a terminal elimination half-life of about 22 hours. Steady-state studies in hypertensive patients given doxazosin doses of 2 to 16 mg once daily showed linear kinetics and dose proportionality. In two studies, following the administration of 2 mg orally once daily, the mean accumulation ratios (steady-state AUC vs. first-dose AUC) were 1.2 and 1.7. Enterohepatic recycling is suggested by secondary peaking of plasma doxazosin concentrations. In a study of two subjects administered radiolabelled doxazosin 2 mg orally and 1 mg intravenously on two separate occasions, approximately 63% of the dose was eliminated in the feces and 9% of the dose was found in the urine. On average only 4.8% of the dose was excreted as unchanged drug in the feces and only a trace of the total radioactivity in the urine was attributed to unchanged drug. Specific Populations Geriatric The pharmacokinetics of doxazosin mesylate in young (< 65 years) and elderly (≥65 years) subjects were similar for plasma half-life values and oral clearance. Renal Impairment Pharmacokinetic studies in elderly patients and patients with renal impairment have shown no significant alterations compared to younger patients with normal renal function. Hepatic Impairment Administration of a single 2 mg dose to patients with cirrhosis (Child-Pugh Class A) showed a 40% increase in exposure to doxazosin. The impact of moderate (Child-Pugh Class B) or severe (Child-Pugh Class C) hepatic impairment on the pharmacokinetics of doxazosin is not known [ see Use in Specific Populations (8.6) ]. Drug Interactions There are only limited data on the effects of drugs known to influence the hepatic metabolism of doxazosin (e.g., cimetidine). Cimetidine: In healthy volunteers, the administration of a single 1 mg dose of doxazosin on day 1 of a four-day regimen of oral cimetidine (400 mg twice daily) resulted in a 10% increase in mean AUC of doxazosin, and a slight but not significant increase in mean C max and mean half-life of doxazosin. In vitro data in human plasma indicate that doxazosin mesylate has no effect on protein binding of digoxin, warfarin, phenytoin, or indomethacin.

20230609

1

3 DOSAGE FORMS AND STRENGTHS Doxazosin Tablets, USP: 1 mg, 2 mg, 4 mg, or 8 mg. Each tablet contains doxazosin mesylate equivalent to 1 mg, 2 mg, 4 mg or 8 mg doxazosin (free base). Tablets: 1 mg, 2 mg, 4 mg, 8 mg.

Doxazosin mesylate Doxazosin mesylate LACTOSE MONOHYDRATE MICROCRYSTALLINE CELLULOSE SODIUM LAURYL SULFATE SODIUM STARCH GLYCOLATE TYPE A POTATO MAGNESIUM STEARATE DOXAZOSIN MESYLATE DOXAZOSIN white to off white C;E;105 Doxazosin mesylate Doxazosin mesylate LACTOSE MONOHYDRATE MICROCRYSTALLINE CELLULOSE SODIUM LAURYL SULFATE SODIUM STARCH GLYCOLATE TYPE A POTATO MAGNESIUM STEARATE DOXAZOSIN MESYLATE DOXAZOSIN white to off white C;E;106 Doxazosin mesylate Doxazosin mesylate LACTOSE MONOHYDRATE MICROCRYSTALLINE CELLULOSE SODIUM LAURYL SULFATE SODIUM STARCH GLYCOLATE TYPE A POTATO MAGNESIUM STEARATE DOXAZOSIN MESYLATE DOXAZOSIN white to off white C;E;107 Doxazosin mesylate Doxazosin mesylate LACTOSE MONOHYDRATE MICROCRYSTALLINE CELLULOSE SODIUM LAURYL SULFATE SODIUM STARCH GLYCOLATE TYPE A POTATO MAGNESIUM STEARATE DOXAZOSIN MESYLATE DOXAZOSIN white to off white C;E;108

13.2 Animal Toxicology and Pharmacology An increased incidence of myocardial necrosis or fibrosis was observed in long-term (6–12 months) studies in rats and mice (exposure 8 times human AUC exposure in rats and somewhat equivalent to human C max exposure in mice). Findings were not seen at lower doses. In dogs no cardiotoxicity was observed following 12 months of oral dosing at doses that resulted in maximum plasma concentrations (C max ) 14 times the C max exposure in humans receiving a 12 mg/day therapeutic dose or in Wistar rats at C max exposures 15 times human C max exposure. There is no evidence that similar lesions occur in humans.

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility Carcinogenesis and Mutagenesis: Chronic dietary administration (up to 24 months) of doxazosin mesylate at maximally tolerated doses of 40 mg/kg/day in rats and 120 mg/kg/day in mice revealed no evidence of carcinogenic potential. The highest doses evaluated in the rat and mouse studies are associated with AUCs (a measure of systemic exposure) that are 8 times and 4 times, respectively, the human AUC at a dose of 16 mg/day. Mutagenicity studies revealed no drug- or metabolite-related effects at either chromosomal or subchromosomal levels. Fertility in Males : Studies in rats showed reduced fertility in males treated with doxazosin at oral doses of 20 (but not 5 or 10) mg/kg/day, about 4 times the AUC exposures obtained with a 12 mg/day human dose. This effect was reversible within two weeks of drug withdrawal. There have been no reports of any effects of doxazosin on male fertility in humans.

13 NONCLINICAL TOXICOLOGY

ANDA075646

Doxazosin mesylate

Doxazosin mesylate

62135-051

HUMAN PRESCRIPTION DRUG

ORAL

PACKAGE LABEL.PRINCIPAL DISPLAY PANEL Doxazosin Tablets, USP 1 mg - NDC 62135-051-90 - 90's Bottle Label Doxazosin Tablets, USP 2 mg - NDC 62135-052-90 - 90's Bottle Label Doxazosin Tablets, USP 4 mg - NDC 62135-053-90 - 90's Bottle Label Doxazosin Tablets, USP 8 mg - NDC 62135-054-90 - 90's Bottle Label Doxazosin Tablets, USP 1 mg - NDC 62135-051-90 - 90's Bottle Label Doxazosin Tablets, USP 2 mg - NDC 62135-052-90 - 90's Bottle Label Doxazosin Tablets, USP 4 mg - NDC 62135-053-90 - 90's Bottle Label Doxazosin Tablets, USP 8 mg - NDC 62135-054-90 - 90's Bottle Label

1.1 Benign Prostatic Hyperplasia (BPH) Doxazosin mesylate tablets are indicated for the treatment of the signs and symptoms of BPH.

17 PATIENT COUNSELING INFORMATION Advise the patient to read the FDA-approved patient labeling (Patient Information). Postural Hypotension Advise patients of the possibility of syncopal and orthostatic symptoms, especially at the initiation of therapy, and urged to avoid driving or hazardous tasks for 24 hours after the first dose, after a dosage increase, and after interruption of therapy when treatment is resumed. Advise patients to report symptoms to their healthcare provider. Priapism Advise patients of the possibility of priapism and to seek immediate medical attention if symptoms occur. This product's label may have been updated. For full prescribing information, please visit www.chartwellpharma.com. All brand names listed are the registered trademarks of their respective owners and are not trademarks of Chartwell RX, LLC. Manufactured for: Chartwell RX, LLC. Congers, NY 10920 L71479 Revised 05/2023 Print Patient Information at: www.chartwellpharma.com/our-products/

14 CLINICAL STUDIES

8.5 Geriatric Use Benign Prostatic Hyperplasia (BPH) The safety and effectiveness profile of doxazosin mesylate was similar in the elderly (age ≥ 65 years) and younger (age < 65 years) patients. Hypertension Clinical studies of doxazosin mesylate did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal or cardiac function, and of concomitant disease or other drug therapy.

8.4 Pediatric Use The safety and effectiveness of doxazosin mesylate have not been established in children.

8.1 Pregnancy Risk Summary The limited available data with doxazosin mesylate in pregnant women are not sufficient to inform a drug-associated risk for major birth defects and miscarriage. However, untreated hypertension during pregnancy can result in increased maternal risks [see Clinical Considerations ] . In animal reproduction studies, no adverse developmental effects were observed when doxazosin was orally administered to pregnant rabbits and rats during the period of organogenesis at doses of up to 41 and 20 mg/kg, respectively (exposures in rabbits and rats were 10 and 4 times, respectively, the human AUC exposures with a 12 mg/day therapeutic dose). A dosage regimen of 82 mg/kg/day in the rabbit was associated with reduced fetal survival [see Data ]. The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2–4% and 15–20%, respectively. Clinical Considerations Disease-associated maternal and/or embryo/fetal risk Hypertension in pregnancy increases the maternal risk for pre-eclampsia, gestational diabetes, premature delivery, and delivery complications (e.g., need for cesarean section, and post-partum hemorrhage). Hypertension increases the fetal risk for intrauterine growth restriction and intrauterine death. Data Animal Data Radioactivity was found to cross the placenta following oral administration of labelled doxazosin to pregnant rats. Studies in pregnant rabbits and rats at daily oral doses of up to 41 and 20 mg/kg, respectively (plasma drug concentrations of 10 and 4 times, respectively, the human AUC exposures with a 12 mg/day therapeutic dose), have revealed no evidence of adverse developmental effects. A dosage regimen of 82 mg/kg/day in the rabbit was associated with reduced fetal survival. In peri- and postnatal studies in rats, postnatal development at maternal doses of 40 or 50 mg/kg/day of doxazosin (about 8 times human AUC exposure with a 12 mg/day therapeutic dose) was delayed, as evidenced by slower body weight gain and slightly later appearance of anatomical features and reflexes.

8 USE IN SPECIFIC POPULATIONS Hepatic Impairment: Monitor for hypotension. ( 8.6 , 12.3 )

16 HOW SUPPLIED/STORAGE AND HANDLING Doxazosin Tablets, USP are available as tablets for oral administration. Each tablet contains doxazosin mesylate equivalent to 1 mg, 2 mg, 4 mg, or 8 mg of doxazosin as the free base. NDC and Pack Size Strength Description NDC 62135-051-90 (Bottle of 90) 1 mg White to off-white, round scored tablets, debossed with "C" over bisect" E" on one side and "105" on the other side. NDC 62135-052-90 (Bottle of 90) 2 mg White to off-white, round scored tablets, debossed with "C" over bisect" E" on one side and "106" on the other side. NDC 62135-053-90 (Bottle of 90) 4 mg White to off-white, round scored tablets, debossed with "C" over bisect" E" on one side and "107" on the other side. NDC 62135-054-90 (Bottle of 90) 8 mg White to off-white, round scored tablets, debossed with "C" over bisect "E" on one side and "108" on the other side. Store at 20° to 25°C (68° to 77°F); excursions permitted to 15° to 30°C (59° to 86°F) [see USP Controlled Room Temperature]. Store in a dry place. Keep tightly closed. Avoid excessive heat. Dispense contents in a tight, light-resistant container as defined in the USP with a child-resistant closure, as required. Keep this and all medication out of the reach of children.