Which Drugs or Food Interact With HRT?

Hormone replacement therapy (HRT) is used to replace the hormones that are lost at menopause, and to treat the associated symptoms, including hot flushes, vaginal dryness, loss of sex drive, mood changes, stress incontinence, night sweats, bone thinning, back pain and joint pain.

HRT is normally an oestrogen and a progesterone – the progesterone protects against endometrial cancer (cancer of the womb or uterus lining), so may not be included for women who have had a hysterectomy.

In combined HRT, women either take an oestrogen continuously and a progesterone for 10-14 days a month, or take both continuously.

HRT is given in a number of different ways:

• patch – a thin adhesive patch like a plaster, which delivers the hormones through the skin, and is changed once or twice weekly
• oral – tablets similar to the contraceptive pill, taken daily
• cream – delivers hormones through the vaginal walls
• pessary – a capsule that delivers the hormones through the vaginal walls
• troches – a lozenge that dissolves in the mouth
• intrauterine device (IUD) – the hormones are part of an IUD placed in the womb, and are released over five years
• vaginal ring – delivers hormones through the vaginal walls, changed every three months
• gel – delivers the hormones through the skin, used daily
• implants – the hormones are in pellets placed under the skin, and are delivered over six months

Talk to a pharmacist or doctor if you have any concerns over food or drug interactions, or if you are taking a new drug or food supplement, even if it is a common, over-the-counter one. Carefully read any instructions with the medicine.

What’s in HRT?

Drugs used in HRT include:

• oestrogens – conjugated equine estrogens, dienoestrol, ethinyloestradiol, mestranol, micronised oestradiol, oestradiol, oestradiol valerate, oestriol, oestrone, piperazine oestrone sulphate
• progesterones – dydrogesterone, levnorgestrel, medroxyprogesterone acetate, norethisterone (norethindrone), norgestrel
• oestrogen/progesterone mimic – tibolone

Food and drug interactions will be similar to those with oral contraceptives – see also ‘Which Drugs or Food Interact With Contraceptives?’

What Drugs Interact With HRT?

Oestrogens can increase production of natural proteins that bind to thyroid hormones. This means that thyroid hormone replacement therapy may not be as effective.

Oestrogens can reduce the rate that corticosteroids (e.g. prednisone) are broken down in the liver, and so could increase their activity and potentially increase side effects. Oestrogens can also increase the activity and toxicity of cyclosporine, used to prevent organ rejection after transplant. Oestrogens can decrease the activity of aromatase inhibitors (used in breast cancer treatment, including anastrozole and exemestane), by blocking their effects.

Tibolone can increase the activity of anticoagulants, potentially causing issues with bleeding.

Certain drugs can increase the breakdown of oestrogens, so reducing their activity. These include barbiturates (anti-anxiety drugs, including amobarbital, butalbital, pentobarbital, phenobarbital and secobarbital), rifampicin (used to treat tuberculosis), HIV protease inhibitors (e.g. amprenavir, nelfinavir, ritonavir), and phenytoin and carbamazepine (used to treat epilepsy).

Certain drugs, when used with oestrogens, can cause liver damage – these include paracetamol (high doses over long periods), anabolic steroids (including nandrolone and oxymetholone), divalproex, valproic acid and phenytoin (used in epilepsy), and chlorpromazine, prochlorperazine and thioridazine (anti-anxiety drugs).

NSAIDs (non-steroidal anti-inflammatory drugs, used to treat inflammation and pain) can increase the risk of heart attack in women using HRT.

What Food Interacts With HRT?

Oestrogens can interact with the herbs black cohosh and saw palmetto, and the supplement DHEA, a naturally occurring hormone. Black cohosh has oestrogen-like effects. The combination of HRT and DHEA can increase the risk of blood clotting, and increase overall hormone levels.

St John’s wort can increase the breakdown of HRT hormones, as can broccoli, cabbage, Brussels sprouts, red wine, alcohol and cigarette smoke. Grapefruit juice can slow the breakdown of HRT hormones.