Injectable weight loss (Mounjaro) drugs, contraception and HRT

Recent guidance has been published in relation to the use of injectable weight loss medication safely as the use may impact your contraception and have an impact on the effectiveness of your HRT to adequately protect your endometrium (womb lining). This increases your risk of cancer.  

For those using injectable weight loss medications, weight loss injections for either weight management or diabetes, please consider the following advice and contact Henfield Medical Centre via the online triage system to make change to medications or arrange a consultation.  

If you are obtaining prescriptions from private provider, discuss the points below with your private provider prior to commencing an injectable weight loss medication and at every dose change.

Contraception:

• All women of reproductive age should use contraception when using injectable weight loss medication. 
• Those taking Tirzepatide (Mounjaro) should switch to a non-oral method e.g. an implant or a coil, or add-in condoms for four weeks after initiation and four weeks after each dose increase, to prevent unwanted pregnancy.
• Those using oral contraception who experience vomiting or severe diarrhoea as a side-effect should follow the missed pills guidance in the pill packet. 
• Please contact the practice if you want to discuss your contraception. 

Hormone replacement therapy: 

• Women with a BMI >30 should be using oestrogen via the skin e.g. patch, gel or spray. If you are not using oestrogen via this method, you are at increased risk of blood clots. Please contact the surgery to arrange a HRT review. 
• Injectable weight loss injections delay gastric emptying and may therefore reduce absorption of oral progestogens. Transdermal or vaginal routes are unlikely to interact. 
• We advise women to switch to a non-oral progesterone (combined patch or levonorgestrel intrauterine device (Mirena coil)) which would be preferable while the injectable weight loss medications are being used. 
• We are very happy to fit a Mirena coil for women at the practice and this would strongly be the recommended guidance to women in this situation. Please contact the surgery to be added to the waiting list.  
• If you do not wish to switch to a Mirena coil or a patch, please remain on your oral progestogen but arrange a consultation to increase the dose. Please be aware that there is uncertainty as to what the correct dose increase might be and whether increasing the dose is enough to ensure safety. 
• A potential approach is to temporarily increase the dose of oral progestogen for 4 weeks after commencing incretin-based therapies, and maintain a higher dose of progestogen with each dose increment on incretin-based therapy until a stable dose is achieved. This is based on extrapolation from COC data and intuitive expert opinion. Uncertainty should be shared with the patient to aid informed decision making.