Tardak / Delmadinone Acetate

(delmadinone acetate)


Tardak, VR Tardak Androgen Inhibitive Suspension
(Drug Manufacturers: Jurox Pty Ltd, Pfizer)


  • Suspension: 10 mg/mL

Availability primarily outside of the USA.


Delmadinone acetate is an antiandrogen having a greater effect than progesterone in its ability to affect testosterone production by restraining interstitial cell function. Its result is to decrease hypersexual behavior or libido.

Antiandrogens are believed to have two modes of action:

  1. inhibit pituitary gonadotrophin release and,
  2. effecting a behavioral sex center.

Tardak’s effects are known to be reversible when the medication is stopped.


Used for aggressiveness and or nervousness in bucks as a form of temporary chemical castration, or as a determinate to whether surgical castration is an option to control aggressive behavior.

Drug Interactions or Contraindications

  • Caution should be used when combining with other types of steroid therapy.

Adverse Reactions

GI: increase in appetite

GU: polyuria, polydipsia

Other:  reduced fertility, reduced libido

Dosage Recommendations

While not licensed for rats, the Pfizer drug company advised that it could be used at the same dose rate and indication as for male dogs and cats:- i.e. 0.1 mL subcutaneous for average 500g rat, and can be repeated 10 days after the first injection if not apparently working or as needed – possibly after 3 – 4 weeks if desired effect wears off. (Additional veterinarian reference of dose use:17)


1 mg/per animal, SQ, IM  42


VET SHOULD FOLLOW INSTRUCTIONS AS ON DATA SHEET. Main indications are for certain forms of aggressiveness and nervousness in male rats. (A form of chemical castration.)

NB Changes in coat color may occur so if this could be a problem e.g. in showing animals other areas of injection may need to be considered.


  • Shake well prior to dosing.
  • Response to drug may not be seen the same day.
  • *Note: male rats remain fertile while on drug even though libido/sexual aggression is diminished.
  • Do not store in an area greater than 25o C. or 77o F., and store away from light.


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