# Situation: A 34-year-old woman who sells vegetables at a public market has bacteriologically confirmed, drug-susceptible pulmonary tuberculosis (TB). She starts the standard 6-month regimen under the National Tuberculosis Program (NTP) at the Rural Health Unit (RHU), with a treatment supporter from the barangay. She lives with her husband and their two children, aged 3 and 8, and takes combined oral contraceptive pills. Which advice should the nurse give her about preventing pregnancy during her TB treatment?

> source: MyMerci (mymerci.kr)  
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> subject: Nursing Practice III — Care of Clients with Problems in Surgery, Oxygenation, Fluid and Electrolytes, Infectious, Inflammatory and Immunologic Response, Cellular Aberrations

## 문제

Situation: A 34-year-old woman who sells vegetables at a public market has bacteriologically confirmed, drug-susceptible pulmonary tuberculosis (TB). She starts the standard 6-month regimen under the National Tuberculosis Program (NTP) at the Rural Health Unit (RHU), with a treatment supporter from the barangay. She lives with her husband and their two children, aged 3 and 8, and takes combined oral contraceptive pills.

Which advice should the nurse give her about preventing pregnancy during her TB treatment?

## 보기

1. Continue the combined pill, since only isoniazid lowers its effect
2. Change to a progestin-only pill taken at the same hour each day
3. Take the combined pill twice daily to make up for the interaction
4. Switch to injections of depot medroxyprogesterone acetate **✔ 정답**

**정답: 4**

## 해설

Rifampicin is a strong liver-enzyme inducer that lowers the level of hormonal contraceptive pills, both combined and progestin-only, so they may fail. Under the program's teaching, she should use a method not affected by this interaction, such as depot medroxyprogesterone acetate injections, a copper intrauterine device, or a barrier method. Doubling pills is unsafe and not recommended.

## 심화 해설

Core mechanism of the interaction

Rifampicin is a potent inducer of hepatic cytochrome P-450 enzymes, especially CYP3A4. It increases the metabolic clearance of estrogen and progestin components in hormonal contraceptives, lowering their serum concentrations below the threshold needed to suppress ovulation. This effect applies to both combined oral contraceptives and progestin-only pills. [1][2]

Because enzyme induction develops over days to weeks, contraceptive failure may not be obvious at the start of treatment, which makes anticipatory counseling essential.

Why the other options are unsafe or ineffective

Watch out! Isoniazid is not the main problem in this interaction. Although isoniazid can inhibit some CYP enzymes, the dominant clinical concern during standard TB treatment is rifampicin’s enzyme induction.

Changing to a progestin-only pill does not solve the problem because rifampicin also accelerates progestin metabolism. [2]

Doubling the combined pill is not recommended. It does not reliably overcome enzyme induction, increases estrogen-related side effects, and has no evidence base for TB treatment.

A copper intrauterine device or depot medroxyprogesterone acetate injection is appropriate because neither relies primarily on hepatic CYP metabolism for contraceptive efficacy. [1][2]

| Method | Interaction with rifampicin | Recommendation during TB treatment |
| --- | --- | --- |
| Combined oral contraceptive | Reduced estrogen and progestin levels due to CYP induction | Avoid or use additional barrier method |
| Progestin-only pill | Reduced progestin levels; same enzyme induction risk | Avoid as sole method |
| Doubled combined pill | Unreliable and increases adverse effects | Not recommended |
| Depot medroxyprogesterone acetate | Minimal reliance on hepatic CYP metabolism | Safe and effective option |
| Copper intrauterine device | No hormonal metabolism interaction | Safe and effective option |

Clinical application in the RHU setting

A woman receiving rifampicin-based TB treatment needs contraception that remains effective despite enzyme induction. The nurse should assess her current method and offer a switch to depot medroxyprogesterone acetate, a copper intrauterine device, or consistent barrier use. The key teaching point is that rifampicin makes hormonal pills unreliable, not that the patient should take more of the same pill.

Key point! Enzyme induction persists for several weeks after rifampicin is stopped, so the interaction does not end on the last day of TB treatment. [1]References (research sources)

- [1]Rifampin drug interactions.Research articleBaciewicz AM, Self TH (1984) · DOI: 10.1001/archinte.144.8.1667

- [2]Oral contraceptive drug interactions.Research articleBaciewicz AM (1985) · DOI: 10.1097/00007691-198503000-00004

## 임상 시나리오

Contraception During Rifampicin-Based TB TreatmentPreventing unintended pregnancy when hormonal methods fail
Rifampicin is a strong hepatic enzyme inducer, mainly of CYP3A4, and lowers serum levels of both estrogen and progestin. This reduces contraceptive efficacy and may lead to ovulation.

Advise the woman to switch to a method not affected by this interaction, such as depot medroxyprogesterone acetate injections, a copper intrauterine device, or a barrier method.

CautionDo not recommend continuing or doubling combined pills, and do not switch to a progestin-only pill. Rifampicin accelerates metabolism of all hormonal contraceptives, and doubling the dose is unsafe and not evidence-based.

## 핵심 개념

- **Enzyme induction** — Process by which a drug such as rifampicin increases hepatic CYP450 activity, accelerating metabolism of other drugs like hormonal contraceptives.
- **Rifampicin** — A key anti-TB drug and potent CYP3A4 inducer that reduces the efficacy of combined and progestin-only oral contraceptives.
- **Depot medroxyprogesterone acetate** — An injectable progestin contraceptive whose efficacy is not primarily dependent on hepatic CYP metabolism, making it suitable during rifampicin therapy.
- **Copper intrauterine device** — A non-hormonal contraceptive method unaffected by rifampicin enzyme induction.
- **CYP3A4** — A major hepatic cytochrome P-450 enzyme induced by rifampicin, responsible for metabolizing estrogen and progestin components.

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