Heparins (unfractionated / dalteparin / enoxaparin)

What is this medication for?

• Thromboembolic disease prophylaxis/treatment: feline ATE, PTE (dog); DIC (mini-dose — increasingly controversial, avoid with concurrent inflammation); LMWHs = at-home ATE prevention mainstay

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.

• Bridge-and-release with warfarin: overlap until INR therapeutic ~5 days, then stop heparin (prevents warfarin-induced protein C dip early).

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

• Injection-site reactions (LMWH) (Local)

Worth a phone call to your veterinarian

• Bleeding (The class effect — UFH > LMWH)
• Heparin-induced low platelet counts (HIT) (Documented (immune); monitor platelets)

⚠️ 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: Severe low platelet counts, uncontrollable active bleeding, hypersensitivity/pork-protein (LMWH)
• has or has had: Renal impairment (LMWH accumulation); peri-operative timing; concurrent antiplatelets

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • Protamine
  • Aspirin/NSAIDs/antiplatelets
  • Warfarin

Storage and handling

UFH multidose vial; LMWH prefilled syringes; under the skin rotation sites.

Good to know

• The feline ATE era shift: UFH in-hospital → LMWH (dalteparin 180 U/kg q4–6h / enoxaparin) at home after the FAT CAT trial questioned warfarin+aspirin — LMWH is now the long-term ATE backbone, and cats need it far oftener than the human label says.
• Protamine reverses UFH fully, LMWHs partially — know which molecule you're fighting.
• DIC mini-dose logic: heparin "spreads" antithrombin over ongoing consumption — controversial, and contraindicated-leaning when inflammation drives the DIC.
• Bridge-and-release with warfarin: overlap until INR therapeutic ~5 days, then stop heparin (prevents warfarin-induced protein C dip early).