Patient Scenarios: Drug Interactions with Contraception

The scenarios are fictitious, but are similar to those experienced by real patients, and are designed to help you reflect on what you have learned after reading the article. They could also be used for group discussion in an education or practice meeting. There are no right or wrong answers, but some pitfalls to avoid.

The following case studies, written by Dr Toni Hazell, relate to her article Key learning points: drug interactions with contraception, and FSRH CEU guidance: drug interactions with hormonal contraception.

Case 1: Shilpi

Context

Shilpi is 32 years old. She has had epilepsy since childhood, and it has proven difficult to manage. It is only in the last year that her consultant has managed to gain control of her seizures, using a complex regimen of three drugs that includes lamotrigine—the other two drugs are not enzyme inducers. She attends your surgery asking for contraception, as she is getting married in 2 months’ time, and has never attended the surgery about anything else.  

Assessment

You are aware that an oestrogen may reduce Shilpi’s lamotrigine level, thereby reducing her epilepsy medications’ effectiveness and potentially risking a seizure, and that desogestrel may increase it, causing a risk of lamotrigine toxicity. You are also aware that lamotrigine appears to reduce exposure to progestogens, risking contraceptive failure. You explain this to Shilpi, but she is unwilling to make any change to her antiepileptics, as she doesn’t want to risk more seizures and the prospect of losing her driving licence again. 

Questions for Reflection

1. What would be the ideal method of contraception for Shilpi?
2. Does Shilpi’s upcoming wedding make any difference to this decision?
3. If Shilpi decides to use a desogestrel-containing method, or another progestogen-containing method, how would you counsel her?

How to Manage This Patient

1. Ideally, Shilpi should use an IUD, IUS, or depot injection, as lamotrigine does not appear to affect the contraceptive effectiveness of these methods
2. The depot injection can cause unpredictable heavy bleeding in the first 3 months of use, which is not ideal for an upcoming wedding, so an IUS or IUD may be more acceptable. If Shilpi is concerned about an IUD fitting, you can reassure her about it is routine to fit IUDs in women who have never had a baby
3. If Shilpi decides to use a progestogen-containing method of contraception, you should explain that there is a risk of reduced contraceptive efficacy because of her lamotrigine use, and that it would therefore be sensible for her to use condoms as well. She may also be at risk of lamotrigine toxicity, so you should advise her to look out for symptoms of this—including diplopia, ataxia, dizziness, drowsiness, and nausea—and report back to you if she experiences them.

Case 2: Megan

Context

Megan is 28 years old and under the care of your local HIV clinic—her HIV is well controlled, and she has had an undetectable viral load for many years. She wants to start some sort of contraception and has come to ask for your advice. 

Assessment

You are aware that Megan may have some issues with drug interactions, but are unsure where to look for advice on contraceptive choice. You also discover that Megan’s antiretrovirals are enzyme inducing.

Questions for Reflection

1. Where would you go for advice in this situation?
2. Considering that Megan is taking enzyme-inducing antiretrovirals, what are her contraceptive options?

How to Manage This Patient

1. The gold-standard resource for this situation is the University of Liverpool HIV drug interaction checker, which is used by HIV consultants and recommended by the FSRH
2. Women taking enzyme inducers have limited options, as they can reduce the contraceptive effectiveness of CHCs, POPs, oral EC, and implants—they should be offered an IUD, an IUS, or the depot injection.

Case 3: Ngozi

Context

Ngozi is a generally healthy 23 year old. The only medication she takes is levothyroxine, which she has taken for several years since being diagnosed with hypothyroidism. You receive a letter from a local sexual and reproductive health clinic stating that they have started her on the combined pill.

Assessment

Ngozi’s dose is stable and she has annual TFTs, the last of which was 4 months ago and yielded normal results. 

Questions for Reflection

1. Are there any concerning interactions here?
2. What should you do?

How to Manage This Patient

1. Oral oestrogens can increase the requirement for levothyroxine because they elevate the level of thyroid-binding globulin
2. The FSRH recommends doing one-off additional TFTs 6 weeks after a patient starts CHC. An increase in levothyroxine dose may be required, although there is no study evidence on this interaction.

FSRH=Faculty of Sexual & Reproductive Health; CEU=Clinical Effectiveness Unit; IUD=intrauterine device; IUS=intrauterine system; CHC=combined hormonal contraception; POP=progestogen-only pill; EC=emergency contraception; TFT=thyroid function test