Altrenogest

What is this medication for?

• Estrus suppression (manage show/mating schedules); pregnancy maintenance in progestin-deficient mares
• Estrus synchronization (Matrix label)
• Luteal insufficiency/pre-term-labor support (extra-label)

How is it given?

Give exactly as your veterinarian prescribed — never change the dose or stop on your own unless your veterinarian has told you to.

• The handler-safety story (gloves, pregnant-women-don't-touch) makes this the inverse of most veterinary drugs: the PATIENT risk is minimal, the HUMAN risk drives the warnings.

What if I miss a dose?

• Give it as soon as you remember — unless it is almost time for the next dose (then skip the missed one; never double up).
• Call your clinic if you miss more than one dose in a row.

Side effects — what should I watch for?

Effects listed as common in this handout

• Reproductive-axis effects (irregular return to estrus, ovarian-cyst reports — class) (Possible)
• Human handler hormonal exposure (The headline risk)

Worth a phone call to your veterinarian

• Uterine infection risk (progestin-compromised defense) (Theoretical)

⚠️ Contact your veterinarian or an emergency clinic IMMEDIATELY if you notice

• Trouble breathing, collapse, seizures, severe vomiting or diarrhea, facial swelling, or pale gums

Before starting (or refilling), tell your veterinarian if your pet:

• has or has had: Use in intended-pregnancy termination contexts (it MAINTAINS pregnancy); mares with uterine infection
• has or has had: Pregnant women/nursing women should not handle; accidental skin contact = wash immediately

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • Oxytocin/PGF2α-class

Storage and handling

Protect from light; gloves for administration (the human-exposure handling warnings are label-mandated).

Good to know

• The 1-mL-per-110-lb arithmetic (0.044 mg/kg) × 15 days is the Regu-Mate mantra — dispensing is mL-based on a graduated dosing syringe.
• The handler-safety story (gloves, pregnant-women-don't-touch) makes this the inverse of most veterinary drugs: the PATIENT risk is minimal, the HUMAN risk drives the warnings.
• Endometrial-cup timing trivia: maintenance past day 60 vs 100–120 reflects when fetal-placental progesterone takes over — reproductive physiology in a dosing note.