This exploratory study will fill a knowledge gap regarding the pharmacokinetic effects of isotretinoin on the etonogestrel (ENG) contraceptive implant.

The Investigators will enroll only women with an etonogestrel contraceptive implant in place who are initiating isotretinoin therapy through their dermatologist. The Investigators will monitor the subjects serum etonogestrel concentration during isotretinoin therapy but no medications will be provided through this study. No medical devices will be inserted as part of this study either.

Inclusion Criteria:

• Have a secondary form of non-hormonal contraception or abstain during isotretinoin therapy and four weeks afterwards
• Have at least two negative pregnancy tests at least 19 days apart prior to initiating isotretinoin therapy
• Have normal baseline laboratory evaluation including liver function tests, basic metabolic panel, and complete blood count
• Willing to abstain from taking any Vitamin A supplement during the study period
• Have a Body Mass Index (BMI) >= 18.5

Exclusion Criteria:

• Currently breastfeeding
• Known contraindications to isotretinoin
• Currently taking any known cytochrome P-450 3A4 enzyme inducers or inhibitors

Reproductive-aged women (18-45) who are under the care of a dermatologist for treatment of acne and planning to initiate therapy with isotretinoin. The women must have chosen an ENG contraceptive implant for their primary mechanism of birth control, placed at least four weeks prior to study enrollment, but in place no longer than three years.

20 weeks from onset of isotretinoin therapy

Collected primarily any pregnancies