Estradiol Enanthate (EEn)

Estradiol Enanthate Injection

Intramuscular (IM) / Subcutaneous (SC)

Estradiol enanthate (EEn) is a medium-to-long-acting injectable estradiol ester with a half-life between estradiol valerate (EV) and estradiol cypionate (EC), at approximately 5-7 days^[1]. It is commonly found as a component of combined injectable contraceptives (e.g. Perlutal) and can also be used as a standalone HRT medication.

Pharmacokinetics

Pharmacokinetic profile of estradiol enanthate^[1]^[2]:

Half-life: ~5-7 days
Peak time: 3-5 days post-injection
Trough time: 7-10 days post-injection
Steady state: Reached after ~3-4 regular cycles

Injectable Estradiol Ester PK Comparison

Parameter	EV (Valerate)	EEn (Enanthate)	EC (Cypionate)
Half-life	~4-5 days	~5-7 days	~8-10 days
Peak time	2-3 days	3-5 days	2-4 days
Recommended interval	5-7 days	7-10 days	7-14 days
Serum level fluctuation	Larger	Moderate	Smaller
Availability	Global	Limited regions	Americas

EEn’s pharmacokinetic profile sits between EV and EC, offering an option for users who want weekly injections with a smoother curve^[3].

Dosing

Adult Dosing

Phase	Dose	Notes
Starting dose	2-4 mg/week	Low-dose start to protect breast development
Maintenance dose	4-6 mg/week	Adjust based on trough E2; target 100-200 pg/mL
Maximum dose	10 mg/10 days	Do not exceed

Dosing references: Endocrine Society 2017^[4] and WPATH SOC 8^[5].

Brands & Availability

Brand	Formulation	Region
Perlutal	EEn 10 mg + DHPA 150 mg (combined contraceptive)	Latin America
Topasel	EEn 10 mg + DHPA 150 mg	Select countries
Single-agent formulations	Various concentrations	Compounding pharmacies

Monitoring

E2: Every 3 months, trough draw (morning before injection). Target 100-200 pg/mL
T: Every 3 months. Target <50 ng/dL
Liver function (ALT/AST): Baseline + every 6 months

Injection Technique

Injection procedure is identical to estradiol valerate injection.