Switching doxazosin XL tablets to doxazosin standard tablets

Rationale for switching

National guidance does not recommend the routine use of doxazosin XL tablets. People should be switched to standard release doxazosin tablets as the preferred option.

NHS England guidance lists doxazosin XL tablets as an item that should not be routinely prescribed in primary care.

Doxazosin XL tablets provide no additional benefit in efficacy and are significantly more expensive than standard release tablets.

People should be switched to standard release doxazosin tablets as the preferred option.

Doxazosin is licensed for the management of hypertension and benign prostatic hyperplasia (BPH) in men. NICE guidance on hypertension in adults and lower urinary tract symptoms in men do not mention any benefits of doxazosin XL tablets over standard release tablets.

Actions for prescribers

Do not initiate doxazosin XL tablets for people with hypertension or for BPH in men.

For people who are already taking doxazosin XL tablets:

• consider whether doxazosin prescribing is in line with NICE guidance on hypertension in adults and lower urinary tract symptoms in men. If prescribing is not aligned, consider de-prescribing following a medication review, including an assessment of patient adherence
• switch to standard release tablets if doxazosin is clinically indicated and prescribing is in line with NICE guidance

Efficacy and tolerability

Doxazosin XL tablets are as effective as doxazosin standard release tablets in the management of hypertension and BPH.

Both formulations of doxazosin are well tolerated, with no apparent differences in the type of adverse effects.

Switching strategies

Three switching strategies for doxazosin XL tablets to doxazosin standard release tablets are suggested in no order of preference.

Choose the most appropriate strategy on a case-by-case basis, considering individual patient factors. The indication for doxazosin does not determine the choice of switching strategy.

Monitoring after the switch

Monitor people for fluctuations in blood pressure after switching them from doxazosin XL tablets to standard release tablets.

Dose titration after the switch

Titrate the dose after one to two weeks of treatment if necessary, as set out in the Summary of Product Characteristics and the BNF section for doxazosin. 

Advice to give people who are switching

• They may experience symptoms of postural hypotension, particularly in the first few hours after switching, symptoms include dizziness, weakness and rarely syncope
• To sit or lie down if they feel dizzy or faint until they feel better and to seek medical attention if significantly affected
• Refer them to NHS patient information on using doxazosin

Comparing doxazosin XL and doxazosin standard release

Licensed dosing

Doxazosin is licensed to be given as a single daily dose regardless of the preparation being used (standard release or XL). The dose can vary from 1mg to 16mg depending on the indication and preparation.  Lower doses are often used initially to help minimise the potential for postural hypotension.

Pharmacokinetic profile

There is little theoretical advantage to using doxazosin XL tablets long term. Both formulations can be taken once daily, as doxazosin has a mean plasma half-life of 22 hours.

Minimum blood levels are similar for both formulations, despite slower absorption and a higher starting dose with XL tablets.

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