What is the appropriate dosing regimen for progesterone (a hormone) at 100 micrograms (mcg)?

Progesterone Dosing Guidelines

For progesterone at 100 mcg (0.1 mg) dosing, there is no standard clinical indication or FDA-approved regimen, as this dose is significantly lower than therapeutic doses used in clinical practice for any condition. 1

Therapeutic Progesterone Dosing by Indication

Preterm Birth Prevention

• Vaginal progesterone for cervical shortening:

  • 100 mg vaginal progesterone nightly from 24-34 weeks for women with singleton pregnancy and prior preterm birth 2
  • 90 mg vaginal gel or 200 mg vaginal suppository daily for singleton pregnancies without prior preterm birth but with cervical length ≤20 mm at 24 weeks 2, 3

• 17-alpha-hydroxyprogesterone caproate (17P):

  • 250 mg IM weekly starting at 16-20 weeks until 36 weeks for singleton pregnancies with prior spontaneous preterm birth 2

Hormone Replacement Therapy

• Postmenopausal women with intact uterus:
  • Cyclic regimen: 200 mg oral progesterone daily for 12-14 days per month 3
  • Continuous regimen: 100 mg oral progesterone daily 3, 4
  • Low-dose option: 100 mg oral progesterone daily for 25 days/month (provides endometrial protection and induces amenorrhea in >90% of women) 4, 5

Functional Uterine Bleeding

• Intramuscular progesterone:
  • 5-10 mg IM daily for six doses 1
  • Bleeding typically ceases within six days

Amenorrhea

• Intramuscular progesterone:

  • 5-10 mg IM for 6-8 consecutive days 1
  • Withdrawal bleeding expected 48-72 hours after last injection

• Secondary amenorrhea:

  • 400 mg oral progesterone at bedtime for 10 days 3
  • Approximately 80% of women experience withdrawal bleeding within 7 days

Assisted Reproduction

• Vaginal progesterone in HRT-FET cycles:
  • Various products with different absorption rates:
    • Cyclogest: 800 mg daily
    • Crinone: 180-270 mg daily
    • Utrogestan/Progestan: 600-800 mg daily
    • Lutinus: 300 mg daily 6
  • Target mid-luteal serum progesterone concentration: 9-11 ng/ml

Important Considerations

Route of Administration

• Oral administration:

  • 90% first-pass hepatic metabolism

  • Higher metabolite levels causing dizziness/drowsiness
  • Less efficient for once-daily dosing 7

• Vaginal administration:

  • Better uterine uptake despite lower systemic levels
  • Bioadhesive gel formulations provide controlled release
  • Fewer systemic side effects 7, 8

• Intramuscular administration:

  • Can cause injection site irritation
  • Higher systemic levels 1

Clinical Pitfalls

1. The 100 mcg (0.1 mg) dose mentioned in the question is 50-8000 times lower than standard therapeutic doses for any indication
2. Micrograms (mcg) vs. milligrams (mg) confusion is a common medication error
3. Natural progesterone has different dosing requirements than synthetic progestins
4. Route of administration significantly impacts bioavailability and required dosing

Conclusion

The 100 mcg (0.1 mg) dose of progesterone mentioned in the question is subtherapeutic for any clinical indication. Standard progesterone dosing ranges from 5-10 mg for IM administration to 100-400 mg for oral administration depending on the indication. Clinicians should verify the intended dose and indication before prescribing.