Doxazosin

Doxazosin is an alpha-adrenergic antagonist drug that is often used to treat high blood pressure (hypertension) and symptoms of benign prostatic hyperplasia (BPH) in men.

The main effect 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.

Additionally, doxazosin may 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 under the supervision of a physician, as it may cause unwanted side effects and interactions with other medications.

Indications Doxazosin

1. Hypertension: Doxazosin is used to treat high blood pressure (hypertension). It helps lower blood pressure by dilating peripheral arteries and veins, which improves blood flow and reduces 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 flow, and other urogenital problems.
3. Relief of urogenital symptoms in women: Doxazosin may sometimes be used to relieve symptoms of urogenital symptoms in women, such as frequent urination or uncontrollable urination.

Release form

1. Tablets: The most common form of doxazosin is oral tablets. Tablets can be either regular or long-acting.
2. Modified-release capsules: Doxazosin is also available in modified-release capsule form, which provides more stable blood levels and can reduce the frequency of dosing to once daily.

Pharmacodynamics

1. Blocking α1-adrenergic receptors: Doxazosin is a selective α1-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 relaxes vascular smooth muscle, which helps dilate arteries and veins, improve blood flow and reduce peripheral resistance.
3. Treatment of symptoms of BPH: In addition to its antihypertensive effects, doxazosin may help reduce symptoms of benign prostatic hyperplasia, such as urinary frequency and heaviness.
4. Long-acting: Doxazosin is usually taken once daily due to its long-lasting action, making it easy to take and maintaining stable blood pressure levels.

Pharmacokinetics

1. Absorption: Doxazosin is usually administered orally in tablet form. After taking the drug, it is quickly and completely absorbed from the gastrointestinal tract, reaching maximum concentration in plasma 2-3 hours after administration.
2. Metabolism: Doxazosin is metabolized in the liver by oxidation, glucuronidation and N-demethylation. The main metabolite is 4-aminomethyl-piperazine-1-carboxamide (M-8), which also has pharmacological activity.
3. Elimination: The released drug and its metabolites are eliminated from the body primarily through the kidneys. In patients with impaired renal function, the dosage should be adjusted as the clearance of doxazosin is reduced.
4. Protein binding: Doxazosin binds to plasma proteins in a small amount (about 98%).
5. Continuous exposure: Some patients may require several weeks of regular use to achieve maximum therapeutic effect.

Dosing and administration

Method of application:

• Doxazosin is usually taken orally, once a day.
• It is best to take the medicine at the same time every day to maintain stable blood levels.
• The tablet can be taken with or without food, but it is important to stick to the same route of administration to ensure that absorption is stable.

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 can be gradually increased (usually to a maximum of 16 mg per day) depending on response to treatment and tolerability.
• Benign prostatic hyperplasia: The starting 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:

• The initiation of treatment and dose increases 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 blood pressure regularly to monitor its level.
• Patients, especially elderly patients, should be careful when getting up from a lying or sitting position to avoid dizziness and possible falls due to a drop in blood pressure.

Use Doxazosin during pregnancy

Using doxazosin (Doxazin) during pregnancy can potentially carry 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 gland.

In a study of the use of doxazosin in a pregnant woman with pheochromocytoma (a catecholamine-secreting tumor that leads to high blood pressure), it was shown that the drug can cross the placental barrier 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 clinical case. However, this study does not provide a complete picture of the safety of the drug, 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 should only be used if the potential benefit to the mother outweighs the possible risks to the fetus. Be sure to consult with your doctor to discuss all your options and risks before taking 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 experienced allergic reactions to other alpha blockers, doxazosin may be dangerous to use.
2. Orthostatic hypotension, or the tendency to experience sudden drops in blood pressure when changing body position (for example, when rising from a sitting or lying position). Doxazosin may worsen this problem.
3. Liver dysfunction. Because doxazosin is metabolized by the liver, its use in patients with hepatic impairment may require dosage adjustments or may be contraindicated depending on the degree of hepatic impairment.

Additionally, it should be borne in mind that when you first take doxazosin or when increasing the dose, the so-called “first dose effect” may occur, when a sharp decrease in blood pressure can lead to dizziness, weakness and even fainting. This is especially important for elderly patients and those 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 sharply when moving from a sitting to a standing position. This may cause dizziness, loss of consciousness, 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. Swelling: Swelling of the extremities or in some cases swelling of the face may occur in some patients.
6. Drowsiness or fatigue: Some patients may experience drowsiness or fatigue when using doxazosin.
7. Ejaculation problems: This may include a decrease in the volume of semen when ejaculating or difficulty ejaculating.
8. Headache: Headache may occur as a result of doxazosin use.
9. Allergic reactions: Including skin rash, itching, angioedema or anaphylaxis (rarely).

Overdose

1. Orthostatic hypotension: An overdose of doxazosin can cause a severe drop in blood pressure when there is a sudden change in body position (for example, when standing up from a sitting or lying position). This can lead to dizziness, fainting and other orthostatic reactions.
2. Tachycardia: Excessive effects of doxazosin on the heart may cause an increase in heart rate, which can 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 lethargy, muscle weakness, slow reaction time, difficulty breathing, and even coma.

Interactions with other drugs

1. Medicines to treat hypertension (antihypertensives): Combining doxazosin with other antihypertensive drugs, such as beta blockers, angiotensin-converting enzyme inhibitors (ACEIs) or diuretics, may result in enhanced hypotensive effects and an increased risk of hypotensive reactions such as 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. Drugs that affect the central nervous system: Doxazosin may enhance the sedative effects of other drugs that affect the central nervous system, such as hypnotics, anxiolytics, or antidepressants.
4. Drugs that affect electrolyte balance: Doxazosin may interact with drugs that affect electrolyte balance, such as diuretics, which may increase the risk of orthostatic hypotension or other adverse effects.
5. Alpha-agonists: Combination with other alpha-agonists may enhance their effect on vascular tone and increase the risk of hypotensive reactions.