Tamoxifen

Mechanism: Selective Estrogen Receptor Modulator (SERM). Blocks estrogen at specific tissues (breast, hypothalamus/pituitary) while acting as an estrogen agonist at others (bone, liver/lipids). Does NOT lower systemic estradiol -- actually raises it.

Dosage:

• Gyno prevention (on-cycle): 10-20 mg/day
• PCT: 20 mg/day for 4-6 weeks (after AAS clearance)
• PCT (aggressive): 40 mg/day for 2 weeks, then 20 mg/day for 2-4 weeks

Administration:

• Oral tablet, with or without food
• Long half-life means once-daily dosing is sufficient

Key Notes:

• FIRST-LINE for gyno prevention -- blocks estrogen at breast tissue without lowering systemic E2
• Preserves the cardiovascular, neurological, and joint benefits of estradiol (unlike AIs)
• Actually improves lipid profile (estrogenic activity at liver)
• In PCT: stimulates GnRH release from hypothalamus, increasing LH/FSH to restart natural testosterone
• Side effects are rare at 10-20mg: occasional vision changes (very rare), mood effects
• Keep on hand during any aromatising cycle as gyno insurance
• For PCT: ensure all AAS have cleared before starting (wait appropriate time based on ester half-life)