What are the adverse effects of Nexgard (afoxolaner) in dogs, and are there safer and more natural alternatives?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: March 29, 2025View editorial policy

Personalize

Help us tailor your experience

Which best describes you? Your choice helps us use language that's most understandable for you.

From the Research

Nexgard (afoxolaner) has been associated with several adverse effects in dogs, including vomiting, diarrhea, lethargy, decreased appetite, and itching, though serious reactions are relatively rare, and safer alternatives such as Frontline Plus (fipronil and S-methoprene) or natural products like cedarwood oil, peppermint oil, or neem oil may be considered. In clinical studies, these side effects occurred in less than 4% of treated dogs 1. For those seeking a safer or more natural alternative, products containing natural ingredients like cedarwood oil, peppermint oil, or neem oil may offer some flea and tick protection, though they are generally less effective than prescription medications. The safety profile of any flea and tick medication depends on the individual dog, with some dogs being more sensitive to certain ingredients than others. Before switching medications, consult with your veterinarian to determine the most appropriate option for your dog based on their specific health needs, lifestyle, and parasite exposure risk. Regular monitoring for any adverse reactions after administering any flea and tick preventative is always recommended. Some studies have shown that afoxolaner has a high efficacy against adult ticks in treated dogs for at least five weeks 2, but the most recent study from 2023 showed that an oral combination of moxidectin, afoxolaner, and pyrantel pamoate is effective for the prevention of heartworm disease in dogs 3. However, when considering the adverse effects and the availability of safer alternatives, it is recommended to consult with a veterinarian to determine the best option for each individual dog. Key points to consider when choosing a flea and tick medication include:

  • Efficacy against the target parasites
  • Safety profile
  • Individual dog's health needs and lifestyle
  • Potential for adverse reactions
  • Availability of safer alternatives. In the context of real-life clinical medicine, the most recent and highest quality study should be prioritized, and in this case, the 2023 study 3 provides the most up-to-date information on the efficacy of afoxolaner in combination with other ingredients for the prevention of heartworm disease in dogs.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.