What is the best topical estrogen patch for a 65-year-old patient transitioning from Lo Loestrin (ethinyl estradiol and norgestrel) to Hormone Replacement Therapy (HRT)?

Transitioning to HRT: Recommended Transdermal Estrogen Patch

For a 65-year-old woman transitioning from Lo Loestrin to HRT, start with a transdermal 17β-estradiol patch delivering 50 μg daily (such as Estraderm MX 50, Systen 50, or Climara 50), combined with micronized progesterone 200 mg orally for 12-14 days per month for endometrial protection. 1

Why Transdermal 17β-Estradiol is the Optimal Choice

Transdermal delivery is strongly preferred over oral estrogen for this patient because:

• Cardiovascular safety: Transdermal estrogen avoids first-pass hepatic metabolism, resulting in lower risk of venous thromboembolism compared to oral estrogen—a critical consideration at age 65 1
• More physiologic hormone levels: Provides stable estradiol levels throughout the day without the peaks and troughs seen with oral administration 1
• Lower thrombotic risk: The avoidance of hepatic first-pass metabolism reduces prothrombotic effects that are particularly concerning in older postmenopausal women 1

Specific Patch Recommendations and Dosing

Start with 50 μg daily transdermal 17β-estradiol patch:

• Apply to clean, dry, intact skin on the lower abdomen, upper buttocks, back, or upper arms 1
• Avoid areas with excessive hair, oily skin, irritation, or friction from clothing 1
• Change patch according to manufacturer instructions (typically twice weekly or once weekly depending on brand) 2
• Peak estradiol levels occur approximately 6-8 hours after application 1

Available patch options include:

• Estraderm MX 50 μg (proven stable and effective) 3
• Systen 50 μg 3
• Climara 50 μg 2

Essential Progestogen Component

Because your patient has an intact uterus, progestogen is mandatory for endometrial protection:

• First choice: Micronized progesterone 200 mg orally daily for 12-14 days per month (sequential regimen) 1, 4
• Alternative options if micronized progesterone is not tolerated:
  • Medroxyprogesterone acetate 10 mg daily for 12-14 days per month 1, 4
  • Dydrogesterone 10 mg daily for 12-14 days per month 1, 4

Micronized progesterone is strongly preferred because it has a superior cardiovascular and thrombotic risk profile compared to synthetic progestins—particularly important given the American Heart Association and American College of Cardiology recommendations 4

Critical Transition Considerations

When switching from Lo Loestrin (ethinyl estradiol) to transdermal 17β-estradiol:

• Discontinue Lo Loestrin and immediately start the transdermal patch—no washout period needed 1
• The 50 μg daily dose provides physiological estrogen replacement appropriate for a 65-year-old 1
• This is a lower dose than what she received with combined oral contraceptives, which is appropriate for HRT 4

Monitoring and Follow-Up Protocol

Structured follow-up is essential:

• Evaluate treatment effect after 3-6 months 1
• Annual clinical review with particular attention to compliance and symptom control 1
• No routine laboratory monitoring required unless prompted by specific symptoms or concerns 1
• Adjust dose according to the patient's tolerance and feeling of wellbeing 4

Important Clinical Pitfalls to Avoid

Common mistakes when transitioning from contraception to HRT:

1. Do not use ethinyl estradiol for HRT: Lo Loestrin contains ethinyl estradiol, which is synthetic and more potent than 17β-estradiol. HRT should use bioidentical 17β-estradiol 5

2. Do not omit progestogen: Even though she was on combined contraception, she still needs progestogen with HRT for endometrial protection 1, 4

3. Do not use continuous combined regimens initially: At age 65, if she's been postmenopausal for years, a sequential regimen (12-14 days of progestogen per month) is preferred initially to establish withdrawal bleeding patterns 4

4. Avoid oral estrogen: Despite her history of oral contraception, transdermal is safer at her age due to lower VTE risk 1

Duration of Therapy Considerations

Use the lowest effective dose for the shortest duration consistent with treatment goals:

• Risks such as venous thromboembolism, coronary heart disease, and stroke occur within the first 1-2 years of therapy 4
• Breast cancer risk increases with longer-term use 4
• Regular reassessment of risks and benefits is recommended 4
• For every 10,000 women taking estrogen and progestin for 1 year, there would be 7 additional coronary heart disease events, 8 more strokes, 8 more pulmonary emboli, and 8 more invasive breast cancers 4

Alternative Considerations

If the 50 μg patch causes side effects or inadequate symptom control:

• Can adjust to 25 μg daily (lower dose) or 75 μg daily (higher dose) based on response 2
• Both 25 μg and 50 μg doses are equally effective at preventing bone loss 6
• The dose should be individualized based on symptom control, not arbitrary age cutoffs 4

If transdermal delivery is contraindicated (chronic skin conditions, poor adhesion):

• Oral 17β-estradiol 1 mg daily can be considered as second-line 5
• Vaginal 17β-estradiol is NOT appropriate for systemic HRT, only for local genitourinary symptoms 5