Castor Oil as Carrier in Testosterone Enanthate Injections
No, castor oil is not used in standard testosterone enanthate formulations—sesame oil is the FDA-approved carrier vehicle. 1
Standard Carrier Oil for Testosterone Enanthate
- Testosterone enanthate injection (USP) is formulated in sesame oil, not castor oil, according to the FDA drug label 1
- Each mL provides 200 mg testosterone enanthate dissolved in sesame oil with 5 mg chlorobutanol as preservative 1
- This sesame oil formulation is administered intramuscularly at typical doses of 100-200 mg every 2 weeks or 50-100 mg weekly 2
Castor Oil Use in Other Testosterone Formulations
- Castor oil is the carrier vehicle for testosterone undecanoate, not testosterone enanthate 3, 4, 5
- Testosterone undecanoate in castor oil is administered as 750 mg (in 4 mL castor oil) initially, then at 4 weeks, then every 10 weeks 2
- The castor oil formulation of testosterone undecanoate requires gluteal intramuscular injection only and carries a specific FDA warning regarding pulmonary oil microembolism 2
- Oral testosterone undecanoate capsules also use castor oil (along with propylene glycol laurate) as the vehicle for lymphatic absorption 6, 7
Clinical Implications of Different Carrier Oils
- Sesame oil (testosterone enanthate/cypionate) allows flexible injection sites including thigh self-injection or gluteal administration 2
- Castor oil (testosterone undecanoate) restricts injection to gluteal site only due to the larger volume (4 mL) and risk of pulmonary complications 2
- Post-injection pain with castor oil formulations peaks immediately after injection, reaches moderate severity, and resolves by day 4 in 80% of patients 4
- The castor oil vehicle in testosterone undecanoate was associated with episodes of sudden-onset non-productive cough with faintness in 1.5% of injections, likely due to pulmonary oil microembolism 3