Introduction

Name

• Altrenogest.

Class of drug

• Synthetic progestogen.

Description

Chemical name

• 17-alpha-allyl-17-beta-hydroxyestra-4,9,11-trien-3-one (allytenbolone).

Molecular formula

• C21H26O2.

Molecular weight

• 310.43.

Physical properties

• Licensed form in the UK is an oral solution, which is clear and light yellow.
• In some other countries, eg Australia, a licensed injectable form is also available.

Storage requirements

• Should be stored in its original bottle and dispensed with care using a syringe and protective clothing (see 'Precautions' below).
• Because of its potential to cause disease in humans and to contaminate the feed of horses other than those being treated (see ‘Precautions’ below), it should be stored safely with particular care well away from children and where it cannot be handled accidentally by anyone not wearing protective clothing, nor by women of childbearing age or those with particular medical conditions.

Uses

Indications

• Licensed for use in mares in vernal transition (ie the transitional period between winter anestrus and the breeding season) for the following reasons:
  • Suppression of estrus during the long periods of estrus which can occur during vernal transition as mares develop waves of ovarian follicles but do not ovulate.This effect occurs whilst the mare is still being treated with altrenogest.
  • Control of the timing of initiation of estrus and synchronization of ovulation. Both of these effects occur after the end of treatment.
• Is also used in various off-license ways, including:
  • Synchronization of estrus in a group of animals, eg embryo transfer donors and recipients.
  • Suppression of estrus behavior in performance mares.
  • In an attempt to support early pregnancies and prevent early embryonic death
  • To promote uterine quiescence in mares with placentitis during pregnancy
  • In an attempt to suppress undesirably aggressive behavior in mares and stallions. Use in male animals is specifically contraindicated on the data sheet.

Administration

Pharmacokinetics

Precautions

Interactions

with other drugs

• Griseofulvin Griseofulvin can alter the effect of Aaltrenogest if both administered to the same animal.

Adverse Reactions

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• De Mestre A M, Rose B V, Chang YM, Wathes D C, Verheyen K L P (2019) Multivariable analysis to determine risk factors associated with early pregnancy loss in thoroughbred broodmares. Theriogenology 124, 18-23 PubMed.
• McConaghy F F, Green L A, Colgan S, Morris L H (2016) Studies of the pharmacokinetic profile, in vivo efficacy and safety of injectable Altrenogest for the suppression of oestrus in mares. Aust Vet 94 (7), 248-55 PubMed.
• Willmann C, Schuler G, Hoffmann B, Parvizi N & Aurich C (2011) Effects of age and Altrenogest treatment on conceptus development and secretion of LH, progesterone and eCG in early-pregnant mares. Theriogenology 75 (3), 421-8 PubMed.
• Storer W, Thompson D L, Gilley R M & Burns P J (2009) Evaluation of injectable sustained release progestin formulations for suppression of estrus and ovulation in mares. J Equine Vet Sci 29 (1), 33-36 VetMedResource.
• Goolsby H A, Brady H A & Prien S D (2004) The off-label use of Altrenogest in stallions: a survey. J Equine Vet Sci 24 (2), 72-75 VetMedResource.
• Daels P F, McCue P M, DeMoraes M J & Hughes J P (1996) Persistence of the luteal phase following ovulation during Altrenogest treatment in mares. Theriogenology 46 (5), 799-811 PubMed.

Other sources of information

• The NOAH Compendium of datasheets of licensed veterinary medicines. Available at: https://www.noahcompendium.co.uk.
• BHA Notice: Altrenogest update. Available at: https://www.britishhorseracing.com (pdf download).
• Veterinary Medicines Directorate. Adverse Reaction Reporting. Available at: https://www.vmd.defra.gov.uk.
• Veterinary Medicines Directorate. Questions and Answers on FDA's Adverse Event Reporting System (FAERS). Available at: https://www.fda.gov/drugs.