For many years, melarsomine adulticide therapy was the gold standard for eliminating canine heartworms. The Philippines once had access to Immiticide, but its phase-out left veterinarians without a registered adulticide option.
In response, many clinics have turned to Simparica Trio as a practical slow kill protocol. What was once considered an alternative has now become a realistic, everyday strategy in local practice.
Why Simparica Trio Works
Simparica Trio combines:
- Sarolaner
- Moxidectin
- Pyrantel
The key ingredient for heartworm management is moxidectin, which:
- Prevents new infections
- Eliminates developing larvae
- Gradually shortens the lifespan of adult worms
Unlike melarsomine, Simparica Trio does not rapidly kill adult worms. With consistent monthly dosing, however, adult worms die off gradually.
Recommended Protocol
- Simparica Trio every 30 days, without interruption
- Doxycycline (10 mg/kg/day for 4 weeks) to reduce Wolbachia bacteria
- Strict exercise restriction
- Regular monitoring and follow-up
Compliance is critical. Missed doses prolong infection.
Expected Timeline
Slow kill therapy requires patience and client education:
- 6 months – Microfilariae often disappear
- 12 months– Some dogs test antigen-negative
- 18 months – Many convert negative
- 24 months or longer – Most infections clear
Heavy worm burdens may take longer.
Retesting Schedule
- Baseline: Antigen test ± microfilaria test
- 6 months: Repeat antigen test
- 12 months: Repeat antigen test
- Every 6 months thereafter until negative
Once antigen-negative, Simparica Trio should be continued permanently as prevention.
Clinical Reminders
Even with slow kill therapy:
- Exercise restriction remains vital
- Worm death can still trigger pulmonary embolism
- Monitor for coughing and exercise intolerance
The Philippine Reality
Heartworm management here is shaped by availability. With melarsomine gone, Simparica Trio slow kill has become the practical standard in many clinics. It may not be the textbook solution, but it allows veterinarians to treat responsibly rather than leave patients untreated.
Sometimes the best medicine is not the ideal medicine—it is the best medicine available.
Dr. Geoff Carullo is a Fellow and the current President of the Philippine College of Canine Practitioners.
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