Minipress

Prazosin, sold under the brand name Minipress, is a prescription medication used to treat high blood pressure.

The drug may also be used to treat patients with an enlarged prostate, congestive heart failure, Raynaud's disease, pheochromocytoma, and Ergot alkaloid poisoning. Some doctors prescribe prazosin to people with post-traumatic stress disorder, as it blocks the body's release of the hormone adrenaline.

Prazosin is one drug in the class of alpha-adrenergic blockers, which work by relaxing the blood vessels so that blood can pass through more easily. Prazosin comes in a tablet and capsule form and is manufactured by Pfizer, Inc.

Prazosin Warnings

You may feel dizzy when you first start prazosin, since it lowers blood pressure. This effect usually stops once your body gets used to the medication. Try not to stand up too quickly.

Older patients may be more sensitive to the side effects of prazosin, especially dizziness and fainting, which can increase the risk of falling.

Before taking this drug, you should tell your doctor if you have a history of the following conditions:

• Heart problems
• Low blood pressure
• Kidney disease
• Narcolepsy
• Prostate cancer

You should tell your doctor that you are taking this medication before having surgery, including eye surgery.

Don't stop taking prazosin without first consulting your physician. Because some conditions may worsen when the medication is stopped abruptly, your dose may need to be gradually decreased.

Pregnancy and Prazosin

Prazosin should only be used during pregnancy if absolutely necessary. The drug passes through breast milk.

Take Minipress exactly as prescribed. Follow the directions on your prescription label carefully. Your doctor will likely start you on a low dose and gradually increase the dose as necessary.

The recommended starting Minipress dose is 1 mg two or three times a day. Your doctor may gradually increase your dose until your maintenance dose is reached.

Daily doses commonly range between 6 mg and 15 mg.

Prazosin is in a group of drugs called alpha-adrenergic (AL-fa ad-ren-ER-jik) blockers. Prazosin relaxes your veins and arteries so that blood can more easily pass through them.

Prazosin is used to treat hypertension (high blood pressure).

Prazosin may also be used for other purposes not listed in this medication guide.

General

Hypertension

• Carefully monitor BP during initial titration or subsequent upward dosage adjustment.500 501

• Goal is to achieve and maintain optimal control of BP; individualize specific target BP based on consideration of multiple factors, including patient age and comorbidities, and currently available evidence from clinical studies.500 501

Administration

Oral Administration

Administer orally in divided doses 2 or 3 times daily.101

Manufacturers make no specific recommendations regarding administration with meals.101 221

Dosage

Available as prazosin hydrochloride; dosage expressed in terms of prazosin.101 b

Individualize dosage according to patient response and tolerance.101 b Initiate at low dosage to minimize frequency of postural hypotension and syncope.101 b

Postural effects are most likely to occur 2–6 hours after a dose; monitor BP during this period after first dose and with any dosage increases.161 500

If therapy is interrupted for a few days, restart using initial dosage regimen.

Pediatric Patients

Initially, 0.05–0.1 mg/kg daily given in 3 divided doses.195 Increase dosage as necessary up to a maximum of 0.5 mg/kg daily given in 3 divided doses.195

Adults

Initially, 1 mg 2 or 3 times daily.101 b Do notinitiate with higher dosages.101 b May increase dosage gradually to 20 mg daily given in divided doses.101 b

Usual maintenance dosage: 6–15 mg daily given in divided doses.101 b

When other hypotensive agents or diuretics are added to existing prazosin therapy, reduce dosage to 1 or 2 mg 3 times daily; gradually increase according to patient's response and tolerance.101 b

Optimum dosage not established.200 201 212 In clinical studies, usual initial dosage was 1 mg at bedtime; dosage was then gradually increased based on patient's response and tolerance.200 201 202 203 204 205 206 207 208 209 210 211 212 217 220 Maintenance dosages of 1–25 mg daily (given once daily at bedtime or in 2 divided doses) have been used.200 203 206 210 212 217 220 225 Some experts recommend a target maintenance dosage of 1–10 mg daily; others recommend a higher target dosage of 2–20 mg daily.224 225

Prescribing Limits

Pediatric Patients

Maximum 0.5 mg/kg daily.195

Adults

Maximum 20 mg daily.101 b Although higher dosages usually do not increase efficacy, a few patients may benefit from ≤40 mg daily.101 b

Special Populations

Hepatic Impairment

No specific dosage recommendations at this time.b

Renal Impairment

Initially, 1 mg twice daily.b Patients with chronic renal failure may require only small dosages.b

Geriatric Patients

No specific dosage recommendations at this time;b generally increase dosage more slowly in geriatric hypertensive patients than in younger adults.153

Contraindications

Known hypersensitivity to prazosin, quinazolines (e.g., alfuzosin, doxazosin, terazosin), or any ingredient in the formulation.101

Warnings/Precautions

Warnings

Like other α-adrenergic blocking agents, marked hypotension, especially in the upright position, can occur; may be accompanied by syncope, palpitations, and other postural effects (e.g., dizziness, lightheadedness, vertigo).101

Postural effects are most common after an initial dose, shortly after dosing (e.g., within 90 minutes), when dosage is rapidly increased, or when other antihypertensive agents are added to therapy.101 b

To decrease risk of excessive hypotension and syncope, initiate therapy at a low dosage (i.e., 1 mg) and titrate slowly; initiate concomitant antihypertensive agents with caution.101 b

If syncope or hypotension occurs, place patient in a recumbent position and institute supportive therapy as necessary.101 b

General Precautions

IFIS observed during cataract surgery in some patients currently receiving or previously treated with α1-adrenergic blocking agents.101 218

If patient has received α1-blockers, ophthalmologist should be prepared to modify the surgical technique (e.g., through use of iris hooks, iris dilator rings, viscoelastic substances) to minimize complications of IFIS.101 218

Benefit of discontinuing α1-blockers, including prazosin, prior to cataract surgery not established.101 218

Exclude possibility of prostate cancer before initiation of therapy for BPH.155 156

Specific Populations

Category C.101

Distributed into milk in small amounts.101 Caution if used in nursing women.101 b

Safety and efficacy not established in children <18 years of age.101 b

Geriatric patients may be particularly susceptible to postural effects and other adverse effects.153 161

Common Adverse Effects

Dizziness, lightheadedness, headache, drowsiness, lack of energy, weakness, palpitation, nausea.101 b

Protein-bound Drugs

Potential pharmacokinetic interaction (displacement of prazosin or other protein-bound drug).b

Specific Drugs and Laboratory Tests

• Reduces peripheral vascular resistance and BP as a result of vasodilating effects;101 b produces both arterial and venous dilation.101

• Effects appear to result from selective, competitive inhibition of α1-adrenergic receptors.b

• Generally causes no change in heart rate, cardiac output, renal blood flow, and GFR.101 b

• Binds to α-adrenergic receptors on the prostate capsule, prostate adenoma, and 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 and HDL/total cholesterol ratio; small decreases in LDL, total cholesterol, and triglyceride concentrations).153 161 c

• Precise mechanism of action in PTSD not fully elucidated; however, norepinephrine and α1-adrenergic receptors play an important role in the pathophysiology of PTSD-associated nightmares, arousal, selective attention and vigilance.200 201 203 204 205 206 207 208 209 210 216 217 220 Prazosin is believed to help correct the effects of α1-adrenergic receptor hyperstimulation in PTSD and has also been shown to normalize the sleep cycle.200 203 205 206 211 220

Prazosin is used alone or together with other medicines to treat high blood pressure (hypertension). High blood pressure adds to the workload of the heart and arteries. If it continues for a long time, the heart and arteries may not function properly. This can damage the blood vessels of the brain, heart, and kidneys, resulting in a stroke, heart failure, or kidney failure. High blood pressure may also increase the risk of heart attacks. These problems may be less likely to occur if blood pressure is controlled.

Prazosin belongs to the general class of medicines called antihypertensives. It works by relaxing the blood vessels so that blood passes through them more easily. This helps to lower blood pressure. Prazosin may also be used for other conditions as determined by your doctor.

This medicine is available only with your doctor's prescription.

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:

Allergies

Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.

Pediatric

Appropriate studies have not been performed on the relationship of age to the effects of prazosin in the pediatric population. Safety and efficacy have not been established.

Geriatric

No information is available on the relationship of age to the effects of prazosin in geriatric patients.

Pregnancy

Breast Feeding

There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.

Interactions with Medicines

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking this medicine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

• Asenapine
• Tadalafil

Using this medicine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

• Acebutolol
• Alprenolol
• Atenolol
• Betaxolol
• Bevantolol
• Bisoprolol
• Bucindolol
• Carteolol
• Carvedilol
• Celiprolol
• Dilevalol
• Esmolol
• Labetalol
• Levobunolol
• Mepindolol
• Metipranolol
• Metoprolol
• Nadolol
• Nebivolol
• Oxprenolol
• Penbutolol
• Pindolol
• Propranolol
• Sildenafil
• Sotalol
• Talinolol
• Tertatolol
• Timolol
• Vardenafil

Interactions with Food/Tobacco/Alcohol

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

Other Medical Problems

The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:

• Angina (chest pain) or
• Heart disease, severe or
• Postural hypotension (low blood pressure)—Use with caution. May make these conditions worse.

• Cataract surgery—An eye problem called Intraoperative Floppy Iris Syndrome (IFIS) has occurred in patients who are taking or who have recently taken this medicine when they are having cataract surgery. You should tell your ophthalmologist (eye doctor) before your surgery if you are taking prazosin.

• Kidney disease—Use with caution. The effects may be increased because of slower removal of the medicine from the body.

• It is used to treat high blood pressure.
• It may be given to you for other reasons. Talk with the doctor.

• Tell all of your health care providers that you take this medicine (Minipress). This includes your doctors, nurses, pharmacists, and dentists.
• Avoid driving and doing other tasks or actions that call for you to be alert until you see how this medicine affects you.
• To lower the chance of feeling dizzy or passing out, rise slowly if you have been sitting or lying down. Be careful going up and down stairs.
• Have your blood pressure checked often. Talk with your doctor.
• This medicine may affect certain lab tests. Tell all of your health care providers and lab workers that you take this medicine (Minipress).
• If you are having cataract surgery or other eye procedure, talk with your doctor.
• If you are taking this medicine and have high blood pressure, talk with your doctor before using OTC products that may raise blood pressure. These include cough or cold drugs, diet pills, stimulants, ibuprofen or like products, and some natural products or aids.
• Talk with your doctor before you drink alcohol.
• Be careful in hot weather or while being active. Drink lots of fluids to stop fluid loss.
• Tell your doctor if you are pregnant or plan on getting pregnant. You will need to talk about the benefits and risks of using this medicine (Minipress) while you are pregnant.
• Tell your doctor if you are breast-feeding. You will need to talk about any risks to your baby.

Minipress is indicated for the treatment of hypertension, to lower blood pressure. Lowering blood pressure reduces the risk of fatal and nonfatal cardiovascular events, primarily strokes and myocardial infarctions. These benefits have been seen in controlled trials of antihypertensive drugs from a wide variety of pharmacologic classes, including this drug.

Control of high blood pressure should be part of comprehensive cardiovascular risk management, including, as appropriate, lipid control, diabetes management, antithrombotic therapy, smoking cessation, exercise, and limited sodium intake. Many patients will require more than one drug to achieve blood pressure goals. For specific advice on goals and management, see published guidelines, such as those of the National High Blood Pressure Education Program's Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC).

Numerous antihypertensive drugs, from a variety of pharmacologic classes and with different mechanisms of action, have been shown in randomized controlled trials to reduce cardiovascular morbidity and mortality, and it can be concluded that it is blood pressure reduction, and not some other pharmacologic property of the drugs, that is largely responsible for those benefits. The largest and most consistent cardiovascular outcome benefit has been a reduction in the risk of stroke, but reductions in myocardial infarction and cardiovascular mortality also have been seen regularly.

Elevated systolic or diastolic pressure causes increased cardiovascular risk, and the absolute risk increase per mmHg is greater at higher blood pressures, so that even modest reductions of severe hypertension can provide substantial benefit. Relative risk reduction from blood pressure reduction is similar across populations with varying absolute risk, so the absolute benefit is greater in patients who are at higher risk independent of their hypertension (for example, patients with diabetes or hyperlipidemia), and such patients would be expected to benefit from more aggressive treatment to a lower blood pressure goal.

Some antihypertensive drugs have smaller blood pressure effects (as monotherapy) in black patients, and many antihypertensive drugs have additional approved indications and effects (e.g., on angina, heart failure, or diabetic kidney disease). These considerations may guide selection of therapy.

Minipress can be used alone or in combination with other antihypertensive drugs such as diuretics or beta-adrenergic blocking agents.

Minipress is contraindicated in patients with known sensitivity to quinazolines, prazosin, or any of the inert ingredients.

Accidental ingestion of at least 50 mg of Minipress in a two year old child resulted in profound drowsiness and depressed reflexes. No decrease in blood pressure was noted. Recovery was uneventful.

Should overdosage lead to hypotension, support of the cardiovascular system is of first importance. Restoration of blood pressure and normalization of heart rate may be accomplished by keeping the patient in the supine position. If this measure is inadequate, shock should first be treated with volume expanders. If necessary, vasopressors should then be used. Renal function should be monitored and supported as needed. Laboratory data indicate Minipress is not dialysable because it is protein bound.

Applies to prazosin: oral capsule, oral tablet

Along with its needed effects, prazosin (the active ingredient contained in Minipress) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking prazosin:

• Dizziness or lightheadedness, especially when getting up from a lying or sitting position
• fainting (sudden)

• Loss of bladder control
• pounding heartbeat
• swelling of the feet or lower legs

• Chest pain
• trouble breathing

• Painful or prolonged erection of the penis

Some side effects of prazosin may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

• Drowsiness
• headache
• lack of energy

• Dryness of the mouth
• nervousness
• unusual tiredness or weakness

• Frequent urge to urinate
• nausea