What birth control options are suitable for an 18-year-old taking famotidine (histamine-2 (H2) blocker)?

Famotidine Does Not Interact with Birth Control—All Standard Contraceptive Options Are Safe for an 18-Year-Old

Famotidine has no clinically significant drug interactions with hormonal contraceptives, so an 18-year-old taking this H2-blocker can safely use any birth control method appropriate for her age and medical history. 1, 2, 3

Why Famotidine Is Not a Concern

• Famotidine does not bind to cytochrome P-450 enzymes and has not been associated with clinically significant drug interactions with other medications, including hormonal contraceptives 3
• Unlike some medications that affect contraceptive efficacy, famotidine is eliminated primarily through the kidneys (about 70%) as unchanged drug, avoiding hepatic metabolism pathways that could interfere with contraceptive hormones 2

Recommended Contraceptive Approach for This 18-Year-Old

First-Line: Long-Acting Reversible Contraception (LARC)

Counsel adolescents starting with the most effective methods first—LARC methods should be presented as first-line options. 4

Contraceptive Implant (Nexplanon)

• Highest efficacy: <0.05% failure rate with typical use 4
• Single-rod etonogestrel implant effective for 3 years 4
• Can be initiated anytime; if >5 days after menses started, use backup barrier method for 7 days 4
• No examination required before initiation 4
• Ideal for adolescents who prefer a method without regularly scheduled adherence 4
• Common reason for discontinuation is unpredictable bleeding, which can be managed with NSAIDs for 5-7 days if desired 4

Intrauterine Devices (IUDs)

• Levonorgestrel IUD (LNG-IUD): 0.2% typical-use failure rate; Copper IUD (Cu-IUD): 0.8% typical-use failure rate 4
• LNG-IUD options include 52mg (effective 5-8 years) and lower-dose options 4
• Cu-IUD effective for up to 10-12 years 4
• LNG-IUD requires backup method for 7 days if inserted >7 days after menses; Cu-IUD provides immediate protection 4
• Requires bimanual examination and cervical inspection before insertion 4
• Most patients do not require additional STI screening at time of placement unless risk factors present and not recently screened 4

Second-Line: Combined Hormonal Contraceptives (CHCs)

If LARC methods are declined, combined hormonal contraceptives are appropriate next options. 4

Combined Oral Contraceptives (COCs)

• 9% typical-use failure rate 4
• Can be initiated anytime; if >5 days after menses, use backup method for 7 days 4
• Requires blood pressure measurement before initiation 4
• 67% continuation rate at 1 year among all users 4

Contraceptive Patch

• 9% typical-use failure rate, same backup requirements as COCs 4
• Applied weekly for 3 weeks, then 1 week off 4
• Note: Studies in adolescents show mixed continuation rates; one study found only 57% continuation at 1 year versus 76% for pills in adolescents ≤17 years 4
• Contains higher estrogen exposure (1.6 times) than typical COCs, with possible increased VTE risk 4

Vaginal Ring

• 9% typical-use failure rate 4
• Same initiation and backup requirements as other CHCs 4

Third-Line: Progestin-Only Methods

Injectable DMPA (Depo-Provera)

• 6% typical-use failure rate 4
• Given every 12-13 weeks 4
• Can be initiated anytime; if >7 days after menses, use backup for 7 days 4
• 56% continuation rate at 1 year 4

Progestin-Only Pills (POPs)

• 9% typical-use failure rate (combined with CHCs in statistics) 4
• Not typically recommended as first-choice for healthy adolescents due to markedly lower effectiveness than other progestin-only methods (IUD, implant, injectable) 4
• Norethindrone/norgestrel POPs: backup needed for 2 days if >5 days after menses 4
• Drospirenone POP: backup needed for 7 days if >1 day after menses 4
• Only appropriate for adolescents with demonstrated excellent medication adherence 4

Essential Concurrent Recommendation: Barrier Methods

All sexually active adolescents should be counseled to use condoms in addition to their primary contraceptive method for STI protection. 4

• Male condoms: 18% typical-use failure rate for pregnancy, but essential for STI/HIV prevention 4
• Condoms reduce risk of gonorrhea, chlamydia, trichomoniasis, hepatitis B, HIV, herpes, HPV, and syphilis 4
• Must be used with water-based lubricants only (oil-based products weaken latex) 4

Key Clinical Pearls

• Weight/BMI measurement not required to determine medical eligibility for any contraceptive method, though baseline measurement may help address future weight concerns 4
• Emergency contraception counseling and advance provision should be part of anticipatory guidance for all sexually active adolescents 4
• Levonorgestrel emergency contraception (Plan B) available over-the-counter for all ages 4
• Copper IUD is the most effective emergency contraception and can be inserted up to 5 days after unprotected intercourse 4

Common Pitfall to Avoid

Do not assume adolescents cannot use LARC methods due to nulliparity—both IUDs and implants are safe and highly effective first-line options for adolescents regardless of pregnancy history. 4 The outdated concern about IUDs in young women has been thoroughly refuted by current evidence and guidelines.