Doxazosin is a medication used to address high blood pressure (hypertension) and symptoms associated with an enlarged prostate gland (benign prostatic hyperplasia or BPH). This alpha-1 blocker requires proper dosing for effectiveness and patient safety.
Initial Dosing and Titration
Doxazosin therapy typically begins with a low dose, commonly 1 milligram (mg) once daily. This low starting dose minimizes the “first-dose phenomenon,” a sudden drop in blood pressure upon standing (orthostatic hypotension), which can cause dizziness or fainting. This effect is a key concern when starting the medication.
After the initial dose, the medication is gradually increased through a process called titration. Dosage adjustments, such as increasing to 2 mg, 4 mg, and then 8 mg, typically occur at intervals of one to two weeks. This gradual increase allows the body to adapt to the medication and helps reduce the risk of significant blood pressure drops. Taking the first dose, and sometimes subsequent increased doses, at bedtime is often recommended to lessen the impact of potential dizziness or lightheadedness that may occur as the blood pressure adjusts.
Standard Dosing for Conditions
The maintenance dose of doxazosin varies depending on the condition being treated and individual patient response. For managing hypertension, the usual maintenance dose can range from 1 mg to a maximum of 16 mg once daily.
For the treatment of benign prostatic hyperplasia (BPH), the typical maintenance dose usually falls within the range of 2 mg to a maximum of 8 mg once daily. While some overlap exists, the upper limit for BPH dosing is generally lower than for hypertension. The specific dose a patient receives is determined by the healthcare provider based on the individual’s response to the medication and their tolerance of any side effects.
Important Dosing Considerations
When a dose of doxazosin is missed, take it as soon as remembered. However, if it is almost time for the next scheduled dose, skip the missed dose and resume the regular schedule. Do not take a double dose to compensate. If doxazosin therapy is interrupted for several days, restart the medication at the initial low dose and follow the original titration regimen.
Dosing considerations also extend to specific patient populations. Elderly individuals may require lower initial doses due to increased sensitivity and a higher likelihood of orthostatic hypotension. While doxazosin is primarily metabolized by the liver, patients with impaired liver function should use the medication with caution, as their exposure to the drug may increase. Conversely, doxazosin generally does not require dose adjustments for individuals with impaired kidney function, as its pharmacokinetics remain largely unchanged in these patients. Doxazosin can be taken with or without food, as food does not significantly affect its absorption.
Other medications can interact with doxazosin, affecting its dosing and safety. Concomitant use with other blood pressure-lowering medications or phosphodiesterase-5 (PDE5) inhibitors, such as sildenafil, tadalafil, or vardenafil, can lead to dangerously low blood pressure. Patients should be stable on doxazosin therapy before starting a PDE5 inhibitor, and the PDE5 inhibitor should be initiated at its lowest dose.
Monitoring and Adjustments
Healthcare providers monitor a patient’s response to doxazosin to ensure its effectiveness and manage any potential side effects. Regular blood pressure checks are standard to assess how well the medication is controlling hypertension. For BPH, the assessment focuses on improvements in urinary symptoms, such as urinary flow.
Monitoring for side effects is also an ongoing process. Providers particularly watch for symptoms of orthostatic hypotension, including dizziness, lightheadedness, or fainting, especially during initial therapy or after dose increases. Patients are advised to be cautious when changing positions, such as standing up from a sitting or lying position, to mitigate these effects.
Dose adjustments are made based on the patient’s therapeutic response and the presence or absence of side effects. If blood pressure remains elevated or BPH symptoms persist, the dose may be increased according to the titration schedule. Conversely, if side effects become problematic, the dose may be reduced or the medication discontinued. Patients should never adjust their own doxazosin dose; all changes must be made under the guidance of a healthcare professional.