Switching doxazosin XL tablets to doxazosin standard release tablets

Anniessa Patel, Regional Principal Medicines Information Pharmacist, London North West University Healthcare NHS TrustPublished

Doxazosin XL tablets should not routinely be prescribed. Guidance is provided on switching doxazosin XL tablets to standard release tablets.

National guidance

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

NHS England guidance lists doxazosin XL tablets as an item that should not be routinely prescribed in primary care. Doxazosin XL tablets are significantly more expensive than standard release tablets and provide no additional benefit in efficacy.

NICE

Doxazosin is licensed for the management of hypertension or 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 compared to doxazosin standard release tablets for the treatment of hypertension or BPH.

Actions for primary care 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 not, consider de-prescribing following a medication review which should include an assessment of patient adherence.
  • Switch to standard release tablets if doxazosin is clinically indicated and prescribing is in line with NICE guidance.

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.

Hypertension

Doxazosin standard release: daily doses range from 1mg to 16mg
Doxazosin XL: daily doses range from 4mg to 8mg

Benign prostatic hyperplasia

Doxazosin standard release: doses range from 1mg to 8mg
Doxazosin XL: doses range from 4mg to 8mg

Efficacy and tolerability

Doxazosin XL tablets are as effective as doxazosin standard release tablets in the management of hypertension and BPH, as demonstrated by randomised, double-blind, parallel-group trials (some of which are prospective and placebo-controlled).

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

Pharmacokinetic profile

According to pharmacokinetics, there is little theoretical advantage to using doxazosin XL tablets over the long term. Both preparations are suitable for once daily administration as the mean plasma elimination half-life of doxazosin is 22 hours regardless of the formulation. There is no difference in the minimum blood levels of doxazosin achieved by the two formulations despite the slower absorption and a higher starting dose with doxazosin XL tablets.

Switching strategies

Three switching strategies for doxazosin XL tablets to doxazosin standard release tablets are suggested below (in no order of preference).  Decide the best option on a case-by-case basis taking individual patient factors into account.

Switch to half dose of standard release

Example

Switch 4mg once daily doxazosin XL tablets to 2mg once daily standard release tablets.

Monitor for hypertension

Monitor the impact of this switch as some people may require a higher dose or subsequent dose titration.

Switch to same dose of standard release

Example

Switch 4mg once daily doxazosin XL tablets to 4mg once daily standard release tablets.

Monitor for hypotension

Monitor the impact of this switch as some people may experience hypotension and need a lower dose, possibly followed by subsequent dose titration.

Discontinue doxazosin XL and initiate standard release

Example

Discontinue 4mg once daily doxazosin XL tablets and start 1mg once daily standard release tablets at the next scheduled dose.

Monitor for changes in blood pressure

Monitor the impact of this switch as there is a small risk that some people may initially experience hypotension due to the switch or hypertension due to the dose reduction. People will need to be reviewed regularly for dose titration.

Monitoring after the switch

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

The healthcare professional initiating the switch should assess each person individually and any additional monitoring should be done on an individual patient basis.

Dose titration after the switch

If a dose titration is required the recommended titration interval is 1-2 weeks as set out in the summary of product characteristics and the BNF.

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.