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Terazosin

Class: alpha-Adrenergic Blocking Agents
VA Class: CV150
Chemical Name: Piperazine, 1-(4-amino-6,7-dimethoxy-2-quinazolinyl)-4-((tetrahydro-2-furanyl-)carbonyl)-, monohydrochloride, dihydrate
CAS Number: 70024-40-7

Medically reviewed by Drugs.com on Mar 29, 2021. Written by ASHP.

Introduction

Postsynaptic α1-adrenergic blocking agent; quinazoline derivative.

Uses for Terazosin

Hypertension

Management of hypertension alone or in combination with other classes of antihypertensive agents.

Not considered a preferred agent for initial management of hypertension according to current evidence-based hypertension guidelines, but may be useful in the management of resistant hypertension as a component of combination therapy.

Most effective when used in combination with a diuretic; beneficial effects of α1-blockers on blood glucose and lipid concentrations also may mitigate some adverse metabolic effects of diuretics.

Some experts state that an α1-blocker may be a second-line agent in antihypertensive treatment regimens in men with coexisting benign prostatic hyperplasia (BPH); however, the American Urology Association (AUA) states that monotherapy with these drugs is not optimal in hypertensive patients with lower urinary tract symptoms (LUTS) or BPH and that such conditions should be managed separately.

Individualize choice of therapy; consider patient characteristics (e.g., age, ethnicity/race, comorbidities, cardiovascular risk) as well as drug-related factors (e.g., ease of administration, availability, adverse effects, cost).

A 2017 ACC/AHA multidisciplinary hypertension guideline classifies BP in adults into 4 categories: normal, elevated, stage 1 hypertension, and stage 2 hypertension. (See Table 1.)

Source: Whelton PK, Carey RM, Aronow WS et al. 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Hypertension. 2018;71:e13-115.

Individuals with SBP and DBP in 2 different categories (e.g., elevated SBP and normal DBP) should be designated as being in the higher BP category (i.e., elevated BP).

Table 1. ACC/AHA BP Classification in Adults1200

Category

SBP (mm Hg)

DBP (mm Hg)

Normal

<120

and

<80

Elevated

120–129

and

<80

Hypertension, Stage 1

130–139

or

80–89

Hypertension, Stage 2

≥140

or

≥90

The goal of hypertension management and prevention is to achieve and maintain optimal control of BP. However, the BP thresholds used to define hypertension, the optimum BP threshold at which to initiate antihypertensive drug therapy, and the ideal target BP values remain controversial.

The 2017 ACC/AHA hypertension guideline generally recommends a target BP goal (i.e., BP to achieve with drug therapy and/or nonpharmacologic intervention) of <130/80 mm Hg in all adults regardless of comorbidities or level of atherosclerotic cardiovascular disease (ASCVD) risk. In addition, an SBP goal of <130 mm Hg generally is recommended for noninstitutionalized ambulatory patients ≥65 years of age with an average SBP of ≥130 mm Hg. These BP goals are based upon clinical studies demonstrating continuing reduction of cardiovascular risk at progressively lower levels of SBP.

Other hypertension guidelines generally have based target BP goals on age and comorbidities. Guidelines such as those issued by the JNC 8 expert panel generally have targeted a BP goal of <140/90 mm Hg regardless of cardiovascular risk, and have used higher BP thresholds and target BPs in elderly patients compared with those recommended by the 2017 ACC/AHA hypertension guideline.

Some clinicians continue to support previous target BPs recommended by JNC 8 due to concerns about the lack of generalizability of data from some clinical trials (e.g., SPRINT study) used to support the 2017 ACC/AHA hypertension guideline and potential harms (e.g., adverse drug effects, costs of therapy) versus benefits of BP lowering in patients at lower risk of cardiovascular disease.

Consider potential benefits of hypertension management and drug cost, adverse effects, and risks associated with the use of multiple antihypertensive drugs when deciding a patient's BP treatment goal.

For decisions regarding when to initiate drug therapy (BP threshold), the 2017 ACC/AHA hypertension guideline incorporates underlying cardiovascular risk factors. ASCVD risk assessment is recommended by ACC/AHA for all adults with hypertension.

ACC/AHA currently recommend initiation of antihypertensive drug therapy in addition to lifestyle/behavioral modifications at an SBP ≥140 mm Hg or DBP ≥90 mm Hg in adults who have no history of cardiovascular disease (i.e., primary prevention) and a low ASCVD risk (10-year risk <10%).

For secondary prevention in adults with known cardiovascular disease or for primary prevention in those at higher risk for ASCVD (10-year risk ≥10%), ACC/AHA recommend initiation of antihypertensive drug therapy at an average SBP ≥130 mm Hg or an average DBP ≥80 mm Hg.

Adults with hypertension and diabetes mellitus, chronic kidney disease (CKD), or age ≥65 years are assumed to be at high risk for cardiovascular disease; ACC/AHA state that such patients should have antihypertensive drug therapy initiated at a BP ≥130/80 mm Hg. Individualize drug therapy in patients with hypertension and underlying cardiovascular or other risk factors.

In stage 1 hypertension, experts state that it is reasonable to initiate drug therapy using the stepped-care approach in which one drug is initiated and titrated and other drugs are added sequentially to achieve the target BP. Initiation of antihypertensive therapy with 2 first-line agents from different pharmacologic classes recommended in adults with stage 2 hypertension and average BP >20/10 mm Hg above BP goal.

Benign Prostatic Hyperplasia

Reduction of urinary obstruction and relief of associated manifestations in patients with symptomatic BPH.

Although drug therapy usually is not as effective as surgical therapy, it may provide adequate symptomatic relief with fewer and less serious adverse effects compared with surgery.

May consider combined therapy with an α1-adrenergic blocker and 5α-reductase inhibitor for men with bothersome moderate to severe BPH and demonstrable prostatic enlargement. Has been more effective than therapy with either drug alone in preventing long-term BPH symptom progression. Men at risk for BPH progression are most likely to benefit from combination therapy.

Terazosin Dosage and Administration

General

BP Monitoring and Treatment Goals

  • Monitor BP regularly (i.e., monthly) during therapy and adjust dosage of the antihypertensive drug until BP controlled.

  • If unacceptable adverse effects occur, discontinue drug and initiate another antihypertensive agent from a different pharmacologic class.

  • If adequate BP response not achieved with a single antihypertensive agent, either increase dosage of single drug or add a second drug with demonstrated benefit and preferably a complementary mechanism of action (e.g., ACE inhibitor, angiotensin II receptor antagonist, calcium-channel blocker, thiazide diuretic). Many patients will require ≥2 drugs from different pharmacologic classes to achieve BP goal; if goal BP still not achieved with 2 antihypertensive agents, add a third drug.

Administration

Oral Administration

Food may delay time to peak plasma concentrations by about 40 minutes but has little effect on extent of absorption. Manufacturer makes no specific recommendations regarding administration with meals.

Hypertension

Administer initial dose at bedtime; may administer maintenance doses in the morning.

Administer once daily or, if needed for optimal BP control, in 2 divided doses at 12-hour intervals.

BPH

Administer once daily at bedtime.

Dosage

Available as terazosin hydrochloride; dosage expressed in terms of terazosin.

Individualize dosage according to patient response and tolerance. Initiate at low dosage to minimize frequency of postural hypotension and syncope.

Monitor BP 2–3 hours after dosing and at end of dosing interval to determine whether peak and trough responses are similar and to assess potential manifestations (e.g., dizziness, palpitations) of an excessive response.

If therapy is interrupted for several days or longer, restart using initial dosage regimen.

Pediatric Patients

Hypertension†
Oral

Some experts have recommended an initial dosage of 1 mg once daily. Increase dosage as necessary up to a maximum of 20 mg once daily. (See Pediatric Use under Cautions.)

Adults

Hypertension
Oral

Initially, 1 mg daily at bedtime. May increase dosage gradually to 5 mg daily, with further titration up to 20 mg daily if BP is not controlled.

Each increase should be delayed until BP has stabilized at a given dosage.

Usual maintenance dosage: Some experts state 1–20 mg daily, administered as a single dose or in 2 divided doses daily.

BPH
Oral

Initially, 1 mg daily at bedtime. May increase daily dosage to 2 mg and thereafter to 5 mg and 10 mg, if necessary, to reduce symptoms and/or improve urinary flow rates.

Prescribing Limits

Pediatric Patients

Hypertension†
Oral

Maximum 20 mg daily.

Adults

Hypertension
Oral

Maximum 40 mg daily; however, dosages >20 mg daily do not appear to improve BP control.

BPH
Oral

Maximum 20 mg daily.

Special Populations

Hepatic Impairment

Manufacturer makes no specific dosage recommendations; effects on the pharmacokinetics of terazosin have not been elucidated.

Renal Impairment

Clinically important alterations in the pharmacokinetics of terazosin not observed to date; dosage adjustment not necessary.

Administration of supplemental doses of the drug following hemodialysis does not appear to be necessary.

Geriatric Patients

Use with caution; generally, increase dosage more slowly in geriatric patients than in younger adults.

Cautions for Terazosin

Contraindications

  • Known hypersensitivity to terazosin, quinazolines (e.g., doxazosin, prazosin), or any ingredient in the formulation.

Warnings/Precautions

Warnings

Postural Hypotension

Marked hypotension, especially in the upright position, can occur; may be accompanied by syncope, palpitations, and other postural effects (e.g., dizziness, lightheadedness, vertigo).

Postural effects are most common after an initial dose, shortly after dosing (e.g., within 90 minutes), when dosage is increased, or when therapy is resumed after an interruption exceeding a few days.

To decrease risk of excessive hypotension and syncope, initiate therapy at low dose and titrate carefully, lessen level of salt restriction, and avoid diuretics just prior to initiation of terazosin therapy.

Priapism

Priapism reported rarely; may lead to permanent impotence if not treated promptly. (See Advice to Patients.)

General Precautions

Prostate Cancer

Exclude possibility of prostate cancer before initiation of therapy for BPH.

Specific Populations

Pregnancy

Category C.

Lactation

Not known whether terazosin is distributed into milk. Caution if used in nursing women.

Pediatric Use

Manufacturer states that safety and efficacy not established in patients <21 years of age.

Some experts suggest reserving use of centrally acting antihypertensive agents (e.g., terazosin) for children who do not respond to therapy with 2 or more preferred classes of antihypertensive agents (angiotensin-converting enzyme [ACE] inhibitors, angiotensin II receptor antagonists, long-acting calcium-channel blockers, or thiazide diuretics).

Geriatric Use

Geriatric patients may be particularly susceptible to postural effects and other adverse effects. (See Geriatric Patients under Dosage and Administration.)

Common Adverse Effects

In the treatment of hypertension: dizziness, headache, asthenia (weakness, tiredness, lassitude, fatigue), nasal congestion, peripheral edema, somnolence, nausea, palpitation.

In the treatment of BPH: dizziness, asthenia, headache, postural hypotension, somnolence.

Interactions for Terazosin

Antihypertensive Agents

Possible rapid fall in BP and exacerbation of postural effects. Use with caution; may need to reduce and/or retitrate dosage.

Specific Drugs

Drug

Interaction

Acetaminophen

No interaction observed

β-Blockers (e.g., atenolol, propranolol)

No interaction observed

Allopurinol

No interaction observed

Antacids

No interaction observed

Antihistamines (e.g., chlorpheniramine)

No interaction observed

Captopril

Increased peak plasma concentrations of terazosin

Codeine

No interaction observed

Corticosteroids

No interaction observed

Co-trimoxazole

No interaction observed

Diazepam

No interaction observed

Diuretics, thiazide (e.g., hydrochlorothiazide)

No interaction observed

Erythromycin

No interaction observed

Hypoglycemic agents

No interaction observed

NSAIAs (e.g., aspirin, ibuprofen, indomethacin)

No interaction observed

Sympathomimetic (adrenergic) agents (e.g., phenylephrine, pseudoephedrine)

No interaction observed

Verapamil

Increased AUC of terazosin; decreased time to peak plasma terazosin concentrations

Terazosin Pharmacokinetics

Absorption

Bioavailability

Rapidly and almost completely absorbed from the GI tract following oral administration. Peak plasma concentration attained in about 1 hour.

Food

Food has minimal effect on extent of absorption; however, time to peak plasma concentration is delayed by about 40 minutes.

Distribution

Extent

Not known whether terazosin is distributed into breast milk.

Plasma Protein Binding

90–94%.

Elimination

Metabolism

Extensively metabolized in the liver, with minimal first-pass metabolism.

Elimination Route

Excreted in urine (40%) and in feces (60%).

Half-life

Adults: approximately 12 hours.

Geriatric patients: approximately 14 hours.

Special Populations

In geriatric patients, plasma clearance is decreased by about 30%.

Stability

Storage

Oral

Capsules

20–25°C. Protect from light and moisture.

Actions

  • Reduces peripheral vascular resistance and BP as a result of vasodilating effects; produces both arterial and venous dilation.

  • Binds to α1-adrenergic receptors in the prostate and the bladder trigone, resulting in decreased urinary outflow resistance in men.

  • May improve to limited extent the serum lipid profile (e.g., small increases in HDL/total cholesterol ratio; small decreases in LDL, total cholesterol, and triglyceride concentrations).

Advice to Patients

  • Possible syncopal and orthostatic symptoms, especially at initiation of therapy; importance of avoiding driving or other hazardous tasks for 12 hours after first dose, a dosage increase, or when resumed after therapy interruption.

  • Importance of sitting or lying down when symptoms of lowered BP occur, and of rising carefully from a sitting or lying position.

  • Importance of informing clinician if bothersome dizziness, lightheadedness, or palpitations occur.

  • Possible drowsiness or somnolence; use caution when operating machinery or driving a motor vehicle until effects on individual are known.

  • Importance of men seeking medical treatment if painful or sustained (for hours) erection occurs.

  • Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.

  • Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as concomitant illnesses.

  • Importance of advising patients of other important precautionary information. (See Cautions.)

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

Terazosin Hydrochloride

Routes

Dosage Forms

Strengths

Brand Names

Manufacturer

Oral

Capsules

1 mg (of terazosin)*

Terazosin Hydrochloride Capsules

2 mg (of terazosin)*

Terazosin Hydrochloride Capsules

5 mg (of terazosin)*

Terazosin Hydrochloride Capsules

10 mg (of terazosin)*

Terazosin Hydrochloride Capsules

AHFS DI Essentials™. © Copyright 2021, Selected Revisions April 8, 2019. American Society of Health-System Pharmacists, Inc., 4500 East-West Highway, Suite 900, Bethesda, Maryland 20814.

† Use is not currently included in the labeling approved by the US Food and Drug Administration.

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