How can I determine if a progesterone product is micronized?

How to Determine if Progesterone is Micronized

Check the product labeling for the term "micronized progesterone" and look for peanut oil in the inactive ingredients list for oral capsules—this is the definitive marker that distinguishes micronized from non-micronized formulations.

Key Identifying Features

Product Labeling and Formulation

• Oral micronized progesterone capsules will explicitly state "micronized progesterone" as the active ingredient and contain peanut oil as a critical inactive ingredient that serves as the excipient for the micronized hormone 1, 2.
• The FDA-approved oral formulation lists "micronized progesterone" (100 mg or 200 mg) as the active ingredient, with peanut oil, lecithin, gelatin, and glycerin as inactive ingredients 2.
• Vaginal formulations of micronized progesterone do not contain peanut oil, making them suitable for patients with severe peanut allergies 3, 1.

Common Formulations in Clinical Use

The most studied and widely used micronized progesterone formulations include:

• 90-mg (8%) progesterone gel for vaginal use 4
• 200-mg micronized progesterone capsules (can be used orally or vaginally) 4
• 100-mg micronized progesterone capsules for oral use 2

Clinical Context Matters

Why Micronization is Important

• Micronization increases the bioavailability of natural progesterone by creating a pharmacotechnical structure that overcomes rapid liver inactivation after oral administration 5, 6.
• Without micronization, oral progesterone cannot produce adequate plasma and tissue levels due to first-pass hepatic metabolism 6.

Distinguishing from Synthetic Progestins

• Micronized progesterone is natural progesterone, identical to the steroid produced by the corpus luteum, whereas progestins are synthetic molecules 5.
• Synthetic progestins (like norethisterone or medroxyprogesterone acetate) are chemically different compounds and are not micronized progesterone 7.

Critical Pitfall: Peanut Allergy

Patients with severe peanut allergies (anaphylaxis) must avoid oral micronized progesterone capsules because the peanut oil excipient poses a serious risk 1, 2. For these patients:

• Use vaginal gel formulations of micronized progesterone, which do not contain peanut oil 3, 1
• This is particularly important as the American College of Obstetricians and Gynecologists specifically recommends vaginal formulations for patients with severe peanut allergies 3

Practical Verification Steps

When prescribing or dispensing:

1. Review the product label for "micronized progesterone" in the active ingredient section 2
2. Check the inactive ingredients list for peanut oil if it's an oral capsule formulation 1, 2
3. Verify the dosage form: oral capsules (100 mg or 200 mg) or vaginal gel (90 mg/8%) 4, 2
4. Screen for peanut allergies before prescribing oral formulations 3, 1

The brand name products and generic equivalents will all clearly state "micronized" on the packaging and prescribing information if they contain this formulation 2.