Gynaecology - Clomifene or Letrozole for ovulation induction

This information is for you if you have been offered treatment with Clomifene or Letrozole.

What are Clomifene and Letrozole?

Clomifene and Letrozole are drugs that are frequently used for inducing ovulation (production of an egg from the ovary).

Clomifene works by blocking oestrogen receptors, while Letrozole works by suppressing oestrogen production.

Benefits of Clomifene or Letrozole treatment

In both cases, the action of these drugs results in the increased production of hormones which stimulate the ovaries to develop ovarian follicles (cysts from which the egg is produced) and help ovulation.

How do I take the medication?

Your treatment starts with the first day of your period.

If you have irregular periods that are more than 6 weeks apart, you may need to take progesterone tablets to induce a ‘period’ so your treatment could start. This will be discussed with you by your doctor or nurse. For this purpose, Medroxyprogesterone or Norethisterone tablets are typically used.

Before taking Medroxyprogesterone or Norethisterone to induce a ‘period’ you should take a urine pregnancy test.

If your pregnancy test is negative, take Medroxyprogesterone tablets 10mg or Norethisterone 15mg once a day for 7 days.
 
You should have a period 7 -10 days later. If not, you should contact the fertility secretaries on 0161 206 5620 or 0161 206
0493.

Please keep a record of your periods during treatment.

If you are starting treatment or changing the Clomifene or Letrozole dose and you need a monitoring scan, you should not have unprotected intercourse in that cycle until the scan is carried out so to reduce the risk of a multiple pregnancy.

You can start your Clomifene or Letrozole treatment as follows:

Day 1 First day of proper bleeding

Day 2 Start Clomifene or Letrozole 1 tablet daily for 5 days

Day 6 Last day to take clomifene or letrozole tablets

You should contact the Early Pregnancy Assessment Unit on 0161 206 1480/ 0095 within the first few days of starting treatment to arrange an appointment for a ‘follicle tracking’ scan between Day 10 and 13.

The scan is to ensure that:

1. There is appropriate response to the treatment. If >2 follicles are present, there will be a significant risk of a multiple pregnancy and you would be advised to abstain from sexual intercourse or use barrier contraception that month. If there is no follicle present you will be asked to increase the dose of your Clomifene or Letrozole to 2 or 3 tablets daily in a step-wise way. You should only increase your dose if you are advised to do so.
2. The lining of the womb has grown properly. If the lining is consistently thin despite evidence of ovulation, your treatment may be changed to an alternative tablet or injections.

If your period starts within 35 days, restart the Clomifene or Letrozole as before. You won’t need to attend for a ‘follicle tracking’ scan if appropriate response was seen on ultrasound scan and no dose changes have been recommended.

If you have been advised to change the dose of Clomifene or Letrozole, contact the Early Pregnancy Assessment Unit on 0161 206 1480/ 0095 within the first few days of starting treatment to arrange an appointment for a ‘follicle tracking’ scan between Day 10 and 13.

Please start regular intercourse at least 2 or 3 times a week from day 8 of your cycle.

If your period does not start by Day 35 then:

• Please do a urine pregnancy test.
• If the test is negative, take Medroxyprogesterone tablets 10mg or Norethisterone 15mg each day for 7 days to induce a period.

On the first day of your period, restart the Clomifene or Letrozole as before but increase the dose by 1 additional tablet to a maximum of 3 tablets daily.

You should contact the Early Pregnancy Assessment Unit on 0161 206 1480/ 0095 within the first few days of starting treatment to arrange an appointment for a ‘follicle tracking’ scan between Day 10 and 13.

When to stop treatment

If even the high dose does not regulate your cycle to between 26 and 35 days or the lining of your womb remains thin, then you should discontinue treatment and contact the fertility secretaries to arrange for a review appointment.

For further advice or questions in relation to this, please telephone the fertility secretaries on 0161 206 5620 or 0161 206 0493 or email them at salford.fertility@nca.nhs.uk and they will pass your message and contact number to one of the medical/ nursing team who will get back to you as soon as they are able.

Are there any side effects to taking these drugs?

The most common side effect of taking Clomifene or Letrozole is hot flushes, as well as occasional fatigue and dizziness.

Risks of Clomifene or Letrozole treatment

Treatment with Clomifene or Letrozole could increase the chance of a multiple pregnancy and might lead ovarian hyperstimulation syndrome (OHSS). OHSS is reaction to fertility drugs taken to increase egg production. OHSS occurs in women who are very sensitive to the fertility medication resulting in too many eggs developing in the ovaries, which become very large and painful. This is a rare event but might require additional monitoring.

Treatment with Letrozole is off-licence as the drug company has not applied for a specific license to allow treatment for fertility.

The risk of congenital abnormalities in babies appears to be low for both Clomifene and Letrozole and is comparable with babies conceived naturally. However, caution is advised to ensure these are not taken accidentally while you are pregnant.
 
If you experience any bothersome side-effects that don’t subside, please get in touch with your care team by contacting the Early Pregnancy Assessment Unit on 0161 206 1480/ 0095 or the fertility secretaries on 0161 206 5620 or 0161 206 0493 or email them at salford.fertility@nca.nhs.uk

Further information

National Institute for Health and Care Excellence (NICE) guideline CG156: Fertility problems: assessment and treatment. Accessible on: https://www.nice.org.uk/guidance/cg156/ifp/chapter/About- this-information

Human Fertilisation and Embryology Authority (HFEA). Risks of fertility treatment. Accessible on: https://www.hfea.gov.uk/ treatments/explore-all-treatments/risks-of-fertility-treatment/