title: Studies of the pharmacokinetic profile, in vivo efficacy and safety of injectable altrenogest for the suppression of oestrus in mares.
abstract: OBJECTIVE
  To investigate the efficacy and safety of the long-acting altrenogest injection (NV Readyserve® injection) for horses.
  
  
  METHODS
  A single-dose pharmacokinetic (PK) study was conducted. The in vivo efficacy study was a blinded, repeated measures design evaluating behaviour scores. The safety study was a non-blinded, controlled, parallel-group, randomised-block design as per the VICH protocol.
  
  
  METHODS
  In the PK study, serial blood samples were obtained for analysis of plasma altrenogest for 150 h following the injection and a non-compartmental PK analysis was performed. For the efficacy study, 12 mares in oestrus were treated; they were monitored daily for 10 days for signs of oestrus during teasing and given a behaviour score that was compared with pretreatment scores. A standard safety study was conducted at 1-, 3- and 5-fold the recommended dosage for 84 days. Physical, haematological and biochemical examinations were performed.
  
  
  RESULTS
  Mean plasma altrenogest concentrations were greater than ≈0.5 ng/mL for 148 h following administration. Oestrous behaviour was suppressed in all mares within 24 h of administration. Two mares returned to oestrus by day 6 and the rest on days 7-10. In the safety study there were no significant differences in the physical and haematological examinations, but minor biochemical changes in muscle enzymes. There was a low incidence of injection site reactions following the 3- and 5-fold dose, predominantly for pectoral injections.
  
  
  CONCLUSIONS
  These studies support the efficacy and safety of a single dose of Readyserve® injection for the suppression of the signs of oestrus in mares for 5-7 days.
authors.affiliation: Ceva Animal Health Pty Ltd, 11 Moores Rd, Glenorie, New South Wales 2157, Australia. finola.mcconaghy@ceva.com.
authors.forename: F F
authors.initials: FF
authors.lastname: McConaghy
authors.affiliation: SCEC Pty Ltd, Northbridge, NSW, Australia.
authors.forename: L A
authors.initials: LA
authors.lastname: Green
authors.affiliation: SCEC Pty Ltd, Northbridge, NSW, Australia.
authors.forename: S
authors.initials: S
authors.lastname: Colgan
authors.affiliation: Equibreed NZ Ltd, Te Awamutu, New Zealand.
authors.forename: L H
authors.initials: LH
authors.lastname: Morris
mesh_terms: D000818:Animals; D004971:Estrus / Q000187:drug effects*; D005260:Female; D006736:Horses / Q000502:physiology*; D007273:Injections, Intramuscular / Q000662:veterinary; D011374:Progesterone / Q000097:blood; D045167:Progesterone Congeners / Q000009:adverse effects / Q000493:pharmacokinetics* / Q000494:pharmacology; D014204:Trenbolone Acetate / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000494:pharmacology
chemical_list: D045167:Progesterone Congeners; C023445:altrenogest; D011374:Progesterone; D014204:Trenbolone Acetate
keywords: altrenogest; equine reproduction; oestrous behaviour; oestrus suppression; pharmacokinetics