Doxazosin
Doxazosin Uses, Dosage, Side Effects, Food Interaction and all others data.
Doxazosin is an alpha-1 antagonist used for the treatment of benign prostatic hypertrophy (BPH) symptoms and hypertension. Other members of this drug class include Prazosin, Terazosin, Tamsulosin, and Alfuzosin. Because of its long-lasting effects, doxazosin can be administered once a day. It is marketed by Pfizer and was initially approved by the FDA in 1990.
Doxazosin decreases standing and supine blood pressure and relieves the symptoms of benign prostatic hypertrophy through the inhibition of alpha-1 receptors.Doxazosin may cause hypotension due to its pharmacological actions. This frequently occurs in the upright position, leading to a feeling of dizziness or lightheadedness. The first dose of doxazosin may lead to such effects, however, subsequent doses may also cause them. The risk of these effects is particularly high when dose adjustments occur or there are long intervals between doxazosin doses. Treatment should be started with the 1 mg dose of doxazosin, followed by slow titration to the appropriate dose. Patients must be advised of this risk and to avoid situations in which syncope and dizziness could be hazardous following the ingestion of doxazosin. Interestingly doxazosin exerts beneficial effects on plasma lipids. It reduces LDL (low-density lipoprotein) cholesterol and triglyceride levels and increases HDL (high-density lipoprotein) cholesterol levels.
A note on priapism risk
| Trade Name | Doxazosin |
| Availability | Prescription only |
| Generic | Doxazosin |
| Doxazosin Other Names | Doxazosin, Doxazosina, Doxazosine, Doxazosinum |
| Related Drugs | amlodipine, lisinopril, metoprolol, losartan, furosemide, hydrochlorothiazide, tamsulosin, nitroglycerin, finasteride, nifedipine |
| Weight | 1mg, 2mg |
| Type | Tablet |
| Formula | C23H25N5O5 |
| Weight | Average: 451.4751 Monoisotopic: 451.185568935 |
| Protein binding | The plasma protein binding of doxazosin is estimated at 98%.. It has also been shown to be bound to the alpha-1 acid glycoprotein. |
| Groups | Approved |
| Therapeutic Class | |
| Manufacturer | Dexcel Pharma Ltd, Harsen |
| Available Country | United Kingdom, United States, Indonesia |
| Last Updated: | September 19, 2023 at 7:00 am |
Uses
Doxazosin is an alpha-1 adrenergic receptor used to treat mild to moderate hypertension and urinary obstruction due to benign prostatic hyperplasia.
Doxazosin is indicated to treat the symptoms of benign prostatic hypertrophy, which may include urinary frequency, urgency, and nocturia, among other symptoms. In addition, doxazosin is indicated alone or in combination with various antihypertensive agents for the management of hypertension. Off-label uses of doxazosin include the treatment of pediatric hypertension and the treatment of ureteric calculi.
Doxazosin is also used to associated treatment for these conditions: Benign Prostatic Hypertrophy, High Blood Pressure (Hypertension), Ureteric calculus
How Doxazosin works
Doxazosin selectively inhibits the postsynaptic alpha-1 receptors on vascular smooth muscle by nonselectively blocking the alpha-1a, alpha-1b, and alpha-1d subtypes. This action on blood vessels decreases systemic peripheral vascular resistance, reducing blood pressure, exerting minimal effects on the heart rate due to its receptor selectivity. Norepinephrine-activated alpha-1 receptors located on the prostate gland and bladder neck normally cause contraction of regional muscular tissue, obstructing urinary flow and contributing to the symptoms of benign prostatic hypertrophy. Alpha-1 antagonism causes smooth muscle relaxation in the prostate and bladder, effectively relieving urinary frequency, urgency, weak urinary stream, and other unpleasant effects of BPH. Recently, doxazosin was found to cause apoptosis of hERG potassium channels in an in vitro setting, possibly contributing to a risk of heart failure with doxazosin use.
Toxicity
LD50 information
The oral LD50 of doxazosin in mice is >1000 mg/kg.
Overdose information
Symptoms of overdose include hypotension, changes in heart rate, and drowsiness. Administer supportive treatment in case of an overdose with doxazosin. Remove unabsorbed doxazosin from the gastrointestinal tract, correct hypotension, and closely monitor vital signs.
Food Interaction
- Avoid alcohol.
- Take with or without food.
Doxazosin Alcohol interaction
[Moderate] GENERALLY AVOID:
The concurrent use of ethanol and alpha-1 adrenergic blockers may cause increased hypotensive effects.
Patients with aldehyde dehydrogenase deficiencies (primarily Asians) may be at a higher risk of this interaction.
The mechanism has not been determined.
Data exist for prazosin and other alpha adrenergic blockers are expected to interact also.
In addition, any patients taking alpha adrenergic blockers may experience excessive orthostatic hypotension with ethanol ingestion, due to ethanol's unopposed vasodilatory effects in the presence of alpha adrenergic blockade.
Patients who develop
a flushing reaction after ethanol ingestion (indicates a possible aldehyde dehydrogenase deficiency) should be advised to avoid ethanol or limit their intake.
All patients should be warned about the possibility of orthostatic hypotension with concurrent ethanol use.
Doxazosin Drug Interaction
Moderate: metoprolol, metoprolol, metoprolol, metoprololUnknown: aspirin, aspirin, aspirin, aspirin, omega-3 polyunsaturated fatty acids, omega-3 polyunsaturated fatty acids, atorvastatin, atorvastatin, clopidogrel, clopidogrel, cyanocobalamin, cyanocobalamin, ascorbic acid, ascorbic acid, cholecalciferol, cholecalciferol
Doxazosin Disease Interaction
Volume of Distribution
The volume of distribution of doxazosin is 1.0-1.9 L/kg. In a study of radiolabeled doxazosin administered to pregnant rats, doxazosin was found to cross the placenta.
Elimination Route
Doxazosin is rapidly absorbed in the gastrointestinal tract and peak concentrations are achieved within 2-3 hours after administration. The bioavailability is about 60%-70%. The intake of food with doxazosin is not expected to cause clinically significant effects.
Half Life
The terminal elimination half-life of doxazosin has been estimated at 9-12 hours according to some resources. The FDA label indicates the elimination half-life of doxazosin is 22 hours.
Clearance
The clearance of doxazosin is low and ranges from approximately 1-2 ml/min/kg.
Elimination Route
In a pharmacokinetic study using a 1 mg IV radiolabeled dose and a 2 mg oral dose, 63% of the ingested doxazosin was found to be excreted in the feces and about 9% of the dose was found to be excreted in the urine. Traces of radiolabeled unchanged drug were found in the urine and about 5% of the administered drug was found as unchanged drug excreted in the feces.
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