What is the recommended dosing regimen for micronized progesterone (Progesterone) 100mg?

Micronized Progesterone 100mg Dosing Regimen

The recommended dosing regimen for micronized progesterone 100mg varies by clinical indication, with sequential regimens typically requiring 100-200mg daily for 12-14 days per month, while continuous regimens may use 100mg daily for 25 days per month to achieve endometrial protection and amenorrhea.

Hormone Replacement Therapy Dosing

Sequential Regimen (with withdrawal bleeding)

• Dosage: 100-200mg daily
• Duration: 12-14 days per 28-day cycle
• Timing: Typically during the latter half of the estrogen cycle
• Administration: Oral (at bedtime to minimize drowsiness)

Continuous Regimen (to avoid withdrawal bleeding)

• Dosage: 100mg daily
• Duration: 25 days per calendar month or 21/28 days
• Administration: Oral (at bedtime)

Clinical Considerations for Dosing

Endometrial Protection

• 100mg daily for 25 days per month provides adequate endometrial protection with 93% amenorrhea rate by the third month of therapy 1
• For women requiring endometrial protection with estrogen therapy, micronized progesterone is considered a first-choice option due to its favorable side effect profile compared to synthetic progestins 2

Route of Administration

• Oral micronized progesterone should be taken at bedtime to minimize the side effect of mild drowsiness 2
• Alternative routes include vaginal administration (100mg daily), which also provides endometrial protection with fewer systemic effects 3

Special Populations

Adolescents with Premature Ovarian Insufficiency (POI)

• For adolescents aged 14-16 years: 100-200mg daily for 12-14 days of the month 4
• Begin cyclic progestogens after at least 2 years of estrogen therapy or when breakthrough bleeding occurs 4

Women with Iatrogenic POI

• Sequential regimens: 200mg oral/vaginal micronized progesterone for 12-14 days every 28 days 4
• Continuous regimens: Lower doses may be used when combined with appropriate estrogen therapy 4

Pharmacological Considerations

• Micronized progesterone has better bioavailability than non-micronized forms 5
• Significant interindividual variability in absorption exists, with serum concentrations ranging widely after a 300mg dose 6
• Absorption may increase with age 6
• Unlike synthetic progestins, micronized progesterone has:
  • No negative effect on lipid profile
  • No adverse impact on blood pressure
  • Anti-mineralocorticoid effects
  • Anti-androgenic properties 5

Monitoring and Adjustments

• Annual clinical review is recommended for women on HRT, with particular attention to compliance 4
• No routine monitoring tests are required but may be prompted by specific symptoms or concerns 4
• Dose adjustments should be based on:
  1. Endometrial response
  2. Bleeding patterns
  3. Patient tolerance and symptoms

Common Pitfalls to Avoid

1. Inadequate dosing: 100mg daily may be insufficient for some women requiring endometrial protection, particularly in sequential regimens where 200mg is often needed
2. Poor timing: Administration during daytime can lead to increased drowsiness; bedtime dosing is preferred
3. Failure to recognize absorption variability: Some patients may require dose adjustments due to significant interindividual variability in absorption
4. Overlooking contraindications: While safer than synthetic progestins, micronized progesterone is generally contraindicated in breast cancer survivors 4

Micronized progesterone at appropriate doses provides effective endometrial protection while minimizing metabolic and vascular side effects commonly associated with synthetic progestins, making it an optimal choice for hormone replacement therapy in most clinical scenarios.