Doxazosin

Doxazosin is a drug from a group of drugs called alpha-adrenergic antagonists that is often used to treat high blood pressure (hypertension) and symptoms of benign prostatic hyperplasia (BPH) in men.

The main action of doxazosin is to dilate peripheral arteries and veins, which leads to a decrease in blood flow resistance and a decrease in blood pressure. Therefore, it is effective in the treatment of hypertension.

In addition, doxazosin can also be used to improve symptoms associated with BPH, such as frequent urination, nighttime urination, difficulty starting urination, and weak or intermittent urinary flow. It works by relaxing the smooth muscle in the bladder neck and prostate, improving urogenital symptoms.

It is important to note that the use of doxazosin should be done under the supervision of a doctor, as it may cause unwanted side effects and interactions with other drugs.

Indications Doxazosin

1. Hypertension: Doxazosin is used to treat high blood pressure (hypertension). It helps lower blood pressure by widening the peripheral arteries and veins, which helps improve blood flow and lower blood pressure.
2. Benign prostatic hyperplasia (BPH): Doxazosin may be used to improve symptoms associated with BPH in men. These symptoms may include frequent urination, difficulty starting urination, weak urinary stream, and other urogenital problems.
3. Relief of urogenital symptoms in women: Doxazosin may sometimes be used to relieve symptoms of urogenital disorders in women, such as frequent urination or uncontrollable urination.

Release form

1. Tablets: The most common form of doxazosin is tablets for oral use. Tablets can be either regular or extended-release.
2. Modified-release capsules: Doxazosin is also available as modified-release (extended-release) capsules, which provide more stable levels of the active substance in the blood and may reduce the frequency of dosing to once a day.

Pharmacodynamics

1. Alpha-1-adrenergic receptor blocking: Doxazosin is a selective alpha-1-adrenergic receptor antagonist. This means that it blocks the action of norepinephrine on these receptors, which leads to vasodilation and a decrease in peripheral vascular resistance. As a result, blood pressure decreases.
2. Smooth muscle relaxation: Doxazosin also causes relaxation of vascular smooth muscle, which helps dilate arteries and veins, improve blood flow and reduce peripheral resistance.
3. Treatment of BPH symptoms: In addition to its antihypertensive effects, doxazosin may help reduce symptoms of benign prostatic hyperplasia, such as urinary frequency and severity.
4. Long-acting: Doxazosin is usually taken once daily due to its long-acting nature, making it convenient to take and helping to maintain stable blood pressure levels.

Pharmacokinetics

1. Absorption: Doxazosin is usually administered orally as a tablet. After oral administration, it is rapidly and completely absorbed from the gastrointestinal tract, reaching peak plasma concentrations 2-3 hours after administration.
2. Metabolism: Doxazosin is metabolized in the liver by oxidation, glucuronidation, and N-demethylation. The major metabolite is 4-aminomethyl-piperazine-1-carboxamide (M-8), which also has pharmacological activity.
3. Elimination: Released drug and its metabolites are eliminated from the body primarily via the kidneys. In patients with renal impairment, dosage adjustments should be made because doxazosin clearance is reduced.
4. Protein binding: Doxazosin binds to plasma proteins to a small extent (about 98%).
5. Continuous Effect: Some patients may require several weeks of regular use to achieve maximum therapeutic effect.

Dosing and administration

Directions for use:

• Doxazosin is usually taken by mouth, once daily.
• It is best to take the medication at the same time each day to maintain stable levels of the drug in the blood.
• The tablet can be taken with or without food, but it is important to stick to the same method of administration to ensure the level of absorption is consistent.

Dosage:

• High blood pressure: The starting dose is usually 1 mg at bedtime to avoid orthostatic hypotension (drop in blood pressure when standing up). The dose may be gradually increased (usually to a maximum of 16 mg daily) depending on response to treatment and tolerability.
• Benign prostatic hyperplasia: The initial dose is also 1 mg per day. Depending on the clinical response and tolerability, the dose can be gradually increased to 2 mg, 4 mg, 8 mg, and a maximum of 8 mg per day.

Special instructions:

• Initiation of treatment and dose increase should be done under the supervision of a physician to minimize the risks associated with a drop in blood pressure.
• During treatment with doxazosin, it is important to measure your blood pressure regularly to monitor its level.
• Patients, especially older patients, should be careful when getting up from a lying or sitting position to avoid dizziness and possible falls due to decreased blood pressure.

Use Doxazosin during pregnancy

Using doxazosin (Doxazine) during pregnancy may have potential risks, as do most medications, especially when there is no data on its safety in pregnant women. Doxazosin is an alpha-blocker that is commonly used to treat high blood pressure and symptoms of an enlarged prostate.

A study of doxazosin use in a pregnant woman with pheochromocytoma (a tumor that secretes catecholamines, leading to high blood pressure) showed that the drug can cross the placenta and enter breast milk. Doxazosin was also found to be effective in controlling high blood pressure before and after delivery without significant side effects in this case. However, this study does not provide a complete picture of the drug's safety, as it is based on only one case (Versmissen et al., 2016).

In light of this, the use of doxazosin during pregnancy should be carefully considered and used only if the potential benefit to the mother outweighs the possible risks to the fetus. Be sure to consult with your doctor to discuss all possible options and risks before starting this or any other medication during pregnancy.

Contraindications

1. Hypersensitivity to doxazosin or other components of the drug. If you are allergic to doxazosin or have allergic reactions to other alpha-blockers, using doxazosin may be dangerous.
2. Orthostatic hypotension, or a tendency to have sudden drops in blood pressure when changing body position (for example, when rising from a sitting or lying position). Doxazosin may increase this problem.
3. Hepatic impairment. Since doxazosin is metabolized in the liver, its use in patients with hepatic impairment may require dosage adjustment or may be contraindicated depending on the degree of hepatic impairment.

Additionally, it should be taken into account that when taking doxazosin for the first time or when increasing the dose, the so-called "first dose effect" may occur, when a sharp decrease in pressure can lead to dizziness, weakness and even fainting. This is especially important for elderly patients and those who are starting treatment with doxazosin.

Side effects Doxazosin

1. Dizziness and weakness: These symptoms may occur due to a decrease in blood pressure when using doxazosin.
2. Orthostatic hypotension: This is a condition in which blood pressure drops suddenly when you go from a sitting to a standing position. This can lead to dizziness, fainting, or even falls.
3. Tachycardia or bradycardia: These are changes in heart rate that may occur with doxazosin.
4. Digestive disorders: Including nausea, vomiting, diarrhea or constipation.
5. Edema: Edema of the extremities or in some cases facial edema may occur in some patients.
6. Drowsiness or tiredness: Some patients may experience drowsiness or tiredness while taking doxazosin.
7. Ejaculation problems: This may include decreased volume of semen when ejaculating or difficulty ejaculating.
8. Headache: Headache may occur as a result of using doxazosin.
9. Allergic reactions: Including skin rash, itching, angioedema or anaphylaxis (in rare cases).

Overdose

1. Orthostatic hypotension: Overdose of doxazosin may cause a severe drop in blood pressure with a sudden change in body position (for example, when standing up from a sitting or lying position). This may lead to dizziness, fainting, and other orthostatic reactions.
2. Tachycardia: Excessive doxazosin action on the heart may cause an increase in heart rate, which may lead to tachycardia (fast heartbeat).
3. Dizziness and Drowsiness: Overdose may cause severe dizziness, drowsiness, weakness and general malaise.
4. Other side effects: Other possible side effects of doxazosin overdose may include confusion, muscle weakness, slow reaction times, difficulty breathing, and even coma.

Interactions with other drugs

1. Medicines for the treatment of arterial hypertension (antihypertensive agents): The combination of doxazosin with other antihypertensive drugs, such as beta-blockers, angiotensin-converting enzyme inhibitors (ACE inhibitors) or diuretics, may lead to an increased hypotensive effect and an increased risk of hypotensive reactions such as dizziness or syncope.
2. Antiarrhythmic drugs: Combination with antiarrhythmic drugs such as amiodarone or class I or III drugs may enhance their cardiosuppressive effects, which may lead to bradycardia or arrhythmias.
3. CNS (central nervous system) acting drugs: Doxazosin may enhance the sedative effects of other drugs that act on the central nervous system, such as hypnotics, anxiolytics, or antidepressants.
4. Medicines affecting electrolyte balance: Doxazosin may interact with medicines that affect electrolyte balance, such as diuretics, which may increase the risk of orthostatic hypotension or other adverse effects.
5. Alpha-adrenergic agonists: Combination with other alpha-adrenergic agonists may lead to an increase in their effect on vascular tone and increase the risk of hypotensive reactions.