Dosage, Safety & Side Effects Guide
Complete guide to Credelio chewable tablets for dogs — dosage by weight, flea/tick protection duration, side effects, cost, & alternatives.
⚠️ Prescription-Only Medication
Credelio (lotilaner) is a prescription-only medication that requires a valid veterinarian-client-patient relationship. This medication should only be used under direct veterinary supervision. Never administer Credelio without a prescription from your licensed veterinarian, and never adjust the dose on your own.
If your veterinarian has recommended Credelio chewable tablets for your dog, you likely have questions about how it works, what side effects to watch for, and how it compares to other flea and tick preventives on the market. This guide breaks down everything you need to know — from the pharmacology behind lotilaner to real-world dosing, cost expectations, and monitoring tips — so you can walk into your next vet visit fully informed.
What Is Credelio and What Is It Used For in Dogs?
Credelio is a branded oral parasiticide manufactured by Elanco Animal Health. The active ingredient is lotilaner, which belongs to the isoxazoline drug class — the same family that includes Bravecto (fluralaner), NexGard (afoxolaner), and Simparica (sarolaner). Credelio comes as a beef-flavored chewable tablet administered once monthly.
FDA-Approved Uses
The U.S. Food and Drug Administration approved Credelio for dogs in January 2018. Its labeled indications include:
- Flea treatment and prevention: Kills adult Ctenocephalides felis (cat flea) infestations and prevents new infestations for one month
- Tick treatment and control: Kills four tick species — the Lone Star tick (Amblyomma americanum), American dog tick (Dermacentor variabilis), brown dog tick (Rhipicephalus sanguineus), and black-legged tick (Ixodes scapularis)
- Aiding in the treatment of flea allergy dermatitis (FAD): By eliminating fleas, Credelio reduces the allergic skin reactions that plague dogs with flea bite hypersensitivity
Common Off-Label Uses
While not FDA-labeled for these conditions, some veterinarians prescribe isoxazolines off-label for:
- Demodectic mange (Demodex canis): Isoxazolines have demonstrated efficacy against Demodex mites, and Credelio may be used as part of a mange treatment protocol
- Sarcoptic mange (Sarcoptes scabiei): Some clinicians use lotilaner as an alternative to ivermectin-based protocols for sarcoptic mange
Always discuss off-label use thoroughly with your veterinarian, as monitoring requirements may differ from labeled use.
How Does Credelio Work? Mechanism of Action
Mechanism Explainer: Isoxazoline Neurotoxicity
Lotilaner works by inhibiting ligand-gated chloride channels in the parasite's nervous system — specifically, GABA-gated and glutamate-gated chloride channels. These channels regulate the flow of chloride ions across nerve cell membranes, which controls neural excitation.
When lotilaner blocks these channels, parasites experience uncontrolled neural hyperexcitation, leading to seizures, paralysis, and death. The drug is selectively toxic to parasites because mammalian GABA receptors have a different structural configuration, making dogs (and humans) far less sensitive to the compound.
Key pharmacokinetic data:
- Onset of flea kill: begins within 4 hours of administration
- Near-complete flea kill: achieved within 12 hours
- Tick kill onset: within 48 hours for all labeled species
- Duration of efficacy: 35 days (providing a 5-day safety buffer beyond the monthly dosing interval)
- Peak blood concentration (Tmax): approximately 18 hours post-dose
- Elimination half-life: approximately 30 days
Because lotilaner is systemically distributed through the bloodstream, parasites must bite the dog to ingest the drug. This means Credelio does not repel fleas or ticks — it kills them after they feed. For dogs with severe flea allergy dermatitis, your vet may recommend a fast-acting oral adulticide like Capstar (nitenpyram) for immediate relief while Credelio builds protection.
Credelio Dosage by Dog Weight
Credelio is dosed at a minimum of 20 mg/kg (9.07 mg/lb) of lotilaner, administered once every 30 days. The tablets come in six weight-specific strengths. Your veterinarian will prescribe the correct tablet based on your dog's current body weight.
| Dog Weight | Tablet Strength (mg lotilaner) | Tablets per Dose | Frequency |
|---|---|---|---|
| 5.1–12.5 lb (2.3–5.7 kg) | 56.25 mg | 1 | Once monthly |
| 12.6–25 lb (5.7–11.3 kg) | 112.5 mg | 1 | Once monthly |
| 25.1–50 lb (11.3–22.7 kg) | 225 mg | 1 | Once monthly |
| 50.1–100 lb (22.7–45.4 kg) | 450 mg | 1 | Once monthly |
| 100.1–150 lb (45.4–68 kg) | 450 mg + 225 mg | 2 (combined) | Once monthly |
| Over 150 lb (68+ kg) | Per vet calculation | Multiple | Once monthly |
Administration Instructions
- Must be given with food or within 30 minutes of feeding. Lotilaner absorption is significantly reduced on an empty stomach, which can lead to sub-therapeutic blood levels and treatment failure
- The tablet is beef-flavored and chewable — most dogs accept it readily as a treat. If your dog refuses, you can hide it in a small amount of food (pill pocket, peanut butter, cheese)
- If your dog vomits within 1 hour of dosing, contact your veterinarian — a replacement dose may be needed
- Administer on approximately the same date each month for continuous protection
- Safe for puppies 8 weeks of age and older weighing at least 4.4 lb (2 kg)
Side Effects of Credelio: What to Watch For
Like all isoxazolines, Credelio carries a risk of neurologic adverse events. The FDA issued a safety alert in September 2018 regarding the entire isoxazoline class. Most dogs tolerate Credelio well, but understanding the frequency and severity of potential reactions helps you make informed decisions with your vet.
| Side Effect | Frequency | Typical Onset | Severity |
|---|---|---|---|
| Vomiting | ~2.8% | Within 24 hours | Mild |
| Diarrhea | ~1.8% | Within 24–48 hours | Mild |
| Decreased appetite | ~0.7% | Within 24 hours | Mild |
| Lethargy | ~0.5% | Within 24 hours | Mild–Moderate |
| Muscle tremors / ataxia | <0.2% | Within 24–72 hours | Moderate–Severe |
| Seizures | <0.1% | Within 24–72 hours | Severe |
🚨 When to Call Your Veterinarian Immediately
Seek emergency veterinary care if your dog experiences any of the following after taking Credelio:
- Seizures or convulsions of any duration
- Muscle tremors that persist beyond 30 minutes
- Incoordination, stumbling, or inability to stand (ataxia)
- Repeated vomiting (more than 2 episodes in 12 hours)
- Complete refusal to eat for more than 24 hours
- Signs of an allergic reaction: facial swelling, hives, difficulty breathing
If you suspect an adverse drug reaction, you can also report it to the FDA through the FDA Safety Reporting Portal or contact Elanco's adverse event line at 1-888-332-5656.
Contraindications: Dogs Who Should NOT Take Credelio
While Credelio is safe for the vast majority of dogs, certain conditions require caution or complete avoidance:
Absolute Contraindications
- Puppies under 8 weeks of age — safety has not been established
- Dogs under 4.4 lb (2 kg) — no appropriate tablet strength available
- Known hypersensitivity to lotilaner or any isoxazoline-class drug
Use with Caution (Veterinary Risk-Benefit Assessment Required)
- Dogs with a history of seizures or epilepsy: The FDA's isoxazoline safety alert specifically warns that these products have been associated with adverse neurologic events including muscle tremors, ataxia, and seizures. Dogs with pre-existing seizure disorders may be at elevated risk. Your vet may recommend a non-isoxazoline alternative
- Breeding, pregnant, or lactating dogs: The safety of Credelio in breeding animals has not been conclusively evaluated. Discuss alternatives with your veterinarian
- Dogs with hepatic impairment: Lotilaner is metabolized by the liver; dogs with significant liver disease may have altered drug clearance
- Geriatric dogs with multiple comorbidities: Your vet will weigh the risks of tick-borne disease against potential drug side effects
Drug Interactions with Credelio
Lotilaner has a relatively low drug-interaction profile compared to older parasiticides like ivermectin, but several interactions deserve attention:
| Concurrent Medication | Interaction Type | Clinical Significance | Action Required |
|---|---|---|---|
| Other isoxazolines (Bravecto, NexGard, Simparica) | Duplicate therapy | Increased risk of neurologic toxicity | Never combine — use only one isoxazoline at a time |
| Phenobarbital | Hepatic enzyme induction | May reduce lotilaner efficacy through faster metabolism | Monitor flea/tick kill rate; vet may adjust dosing |
| High-dose corticosteroids | Hepatic enzyme induction | Potential reduction in lotilaner blood levels | Inform vet; monitor efficacy |
| Ivermectin / milbemycin (heartworm preventives) | No known significant interaction | Generally safe to combine at labeled doses | Standard concurrent use is common |
| NSAIDs (carprofen, meloxicam) | No known significant interaction | Widely co-prescribed without adverse events | Standard concurrent use is acceptable |
Always provide your veterinarian with a complete list of every medication, supplement, and over-the-counter product your dog is receiving before starting Credelio.
How Long Does My Dog Need to Be on Credelio?
The duration of Credelio use depends on your geographic location, your dog's lifestyle, and your veterinarian's assessment of parasite exposure risk.
Year-Round Protection (Recommended in Most U.S. Regions)
The Companion Animal Parasite Council (CAPC) recommends year-round flea and tick prevention for dogs in most of the United States. Fleas can survive indoors throughout winter, and several tick species — particularly the brown dog tick — remain active in heated homes and kennels regardless of outdoor temperature.
Seasonal Protection (Limited Regions)
In northern climates with sustained freezing temperatures (below 28°F / -2°C for extended periods), some veterinarians may recommend a seasonal protocol — typically March through November. However, this approach carries risk: a single warm day can activate questing ticks, and flea pupae in your home carpet can emerge at any time.
Duration for Specific Conditions
- Routine prevention: Continuous monthly dosing, typically for life
- Flea allergy dermatitis management: Minimum 3–6 months of uninterrupted use, often year-round
- Demodectic mange (off-label): Typically 2–4 months, guided by skin scraping results from your vet
- Kennel or shelter environments: Continuous use due to high exposure risk
Monitoring Requirements and Follow-Up
For most healthy dogs on Credelio for routine flea and tick prevention, extensive monitoring is not required. However, the following schedule reflects best practices:
Recommended Monitoring Schedule
| Baseline visit | Weight verification, seizure history review, medication reconciliation |
| Annual wellness exam | Weight check (adjust dose if dog has gained/lost weight), review of efficacy and any side effects |
| If side effects occur | Contact vet within 24–48 hours of symptom onset; may require neurologic exam |
| Off-label mange treatment | Monthly skin scrapings until two consecutive negative results; blood chemistry if long-term use |
| Epileptic dogs | More frequent neurologic monitoring; seizure log review at each visit |
No specific blood work is required for Credelio alone in healthy dogs. However, if your dog is on concurrent medications (e.g., phenobarbital for seizures), your vet may recommend periodic liver enzyme panels (ALT, AST, ALP) as part of overall health monitoring.
Cost of Credelio and Generic Availability
As of 2026, Credelio remains a brand-name-only product — no FDA-approved generic lotilaner tablets for dogs are currently available in the United States. Pricing varies by tablet strength, retailer, and whether you purchase through your veterinarian or an online pharmacy.
Typical Price Ranges (Per Tablet)
| Tablet Strength | Dog Weight Range | Per Tablet | 6-Month Supply | 12-Month Supply |
|---|---|---|---|---|
| 56.25 mg | 5.1–12.5 lb | $18–$22 | $100–$125 | $195–$250 |
| 112.5 mg | 12.6–25 lb | $19–$24 | $108–$135 | $210–$275 |
| 225 mg | 25.1–50 lb | $21–$27 | $118–$150 | $235–$310 |
| 450 mg | 50.1–100 lb | $24–$32 | $135–$180 | $270–$365 |
| 450 + 225 mg | 100.1–150 lb | $42–$55 | $240–$310 | $480–$620 |
Cost-saving tips:
- Many online pharmacies (Chewy Pharmacy, 1-800-PetMeds) offer auto-ship discounts of 5–10%
- Elanco periodically offers manufacturer rebates — check for current promotions at your vet's office
- Some pet insurance plans with wellness add-ons cover a portion of preventive medications
- Purchasing 6- or 12-month supplies typically reduces per-dose cost by 10–15%
Missed Dose and Overdose Protocols
If You Miss a Dose
If you forget to give Credelio on the scheduled date, administer the tablet as soon as you remember — with food. Then resume monthly dosing from that new date. For example, if the dose was due on March 1st but you remembered on March 10th, give the tablet on March 10th and set the next dose for April 10th.
Important: During the gap between doses, your dog may be unprotected. If you live in a high-tick area (Northeast, Upper Midwest, Southeast), perform thorough tick checks daily until the next dose takes full effect (48 hours post-administration).
If an Overdose Occurs
In pre-approval safety studies, dogs received lotilaner at up to 5 times the maximum recommended dose (100 mg/kg) on six occasions at 28-day intervals. No treatment-related adverse effects were observed at this level, indicating a wide margin of safety.
However, massive overdoses (e.g., a small dog consuming an entire box meant for a large dog) could potentially cause neurologic symptoms. If you suspect an overdose:
- Do not induce vomiting unless specifically instructed by your veterinarian
- Note the tablet strength(s) ingested and approximate time of ingestion
- Call your veterinarian or an emergency veterinary clinic immediately
- You can also contact the ASPCA Animal Poison Control Center at (888) 426-4435 (24/7, consultation fee applies) or the Pet Poison Helpline at (855) 764-7661
Alternatives to Credelio: How It Compares
If Credelio isn't the right fit for your dog — due to seizure history, cost, or personal preference — several alternatives exist across different drug classes:
| Product | Active Ingredient | Route | Frequency | Tick Species | Key Differentiator |
|---|---|---|---|---|---|
| Credelio | Lotilaner | Oral | Monthly | 4 species | Fast kill (4 hr onset) |
| Bravecto | Fluralaner | Oral | Every 12 weeks | 4 species | Longest dosing interval |
| NexGard | Afoxolaner | Oral | Monthly | 4 species | Also treats demodectic mange |
| Simparica | Sarolaner | Oral | Monthly | 5 species | Broadest tick coverage |
| Seresto Collar | Imidacloprid + flumethrin | Topical (collar) | 8 months | 3 species | Non-isoxazoline; repels ticks |
| Vectra 3D | Dinotefuran + pyriproxyfen + permethrin | Topical | Monthly | 4 species | Repels + kills; toxic to cats |
| Revolution Plus | Selamectin + sarolaner | Topical | Monthly | 2 species | Also covers heartworm + ear mites |
For dogs with seizure disorders: Topical products like the Seresto collar or Vectra 3D avoid systemic isoxazoline exposure entirely. Your veterinarian can help you weigh the trade-offs — topical products can have variable efficacy depending on bathing frequency and coat type.
For multi-dog households with cats: Avoid permethrin-containing products like Vectra 3D, which are highly toxic to cats. Credelio, Bravecto, NexGard, and Simparica are safe for use in homes with cats.
Frequently Asked Questions About Credelio
Can I give Credelio and a heartworm preventive at the same time?
Yes. Credelio contains no heartworm preventive ingredient, so it must be paired with a separate heartworm medication such as Heartgard Plus (ivermectin/pyrantel), Interceptor Plus (milbemycin/praziquantel), or Revolution (selamectin). This is standard practice — many veterinarians prescribe Credelio alongside a monthly heartworm preventive as a comprehensive parasite control program.
Does Credelio require a blood test before starting?
No specific blood work is required before starting Credelio for flea and tick prevention in a healthy dog. However, if you are also starting a heartworm preventive concurrently, your vet will likely perform a heartworm antigen test first, as administering certain heartworm preventives to a heartworm-positive dog can cause severe reactions.
Can I bathe my dog after giving Credelio?
Yes. Because Credelio is an oral medication distributed through the bloodstream, bathing, swimming, and rain exposure do not affect its efficacy. This is a significant advantage over topical products, which typically require 24–48 hours of drying time before water exposure.
My dog has had a seizure before. Is Credelio safe?
This is a case-by-case decision that must be made with your veterinarian. The FDA's isoxazoline class warning notes that seizures have been reported in dogs receiving these products, even in dogs with no prior seizure history. For dogs with known epilepsy, many veterinarians prefer non-isoxazoline alternatives like the Seresto collar or topical permethrin products (for dog-only households). If the tick-borne disease risk in your area is high and your vet determines that an isoxazoline is warranted, they may choose Credelio with close neurologic monitoring.
Will Credelio kill fleas already on my dog?
Yes. Credelio begins killing existing adult fleas within 4 hours of administration and achieves near-complete kill within 12 hours. However, it does not kill flea eggs or larvae in your home environment. For heavy infestations, your vet may recommend treating your home with an insect growth regulator (IGR) such as methoprene or pyriproxyfen, along with thorough vacuuming and washing of bedding.
How should I store Credelio tablets?
Store Credelio at room temperature, between 59°F and 86°F (15°C–30°C), with brief excursions permitted up to 104°F (40°C). Keep tablets in their original packaging until use, and store out of reach of children and pets to prevent accidental ingestion.
Is Credelio safe for herding breeds like Collies and Australian Shepherds?
Yes. Unlike ivermectin, which can be toxic to dogs with the MDR1 gene mutation (common in Collies, Australian Shepherds, and other herding breeds), lotilaner does not rely on the P-glycoprotein transport system affected by this mutation. Credelio is considered safe for MDR1-mutant dogs at labeled doses.
Disclaimer: This article is for informational purposes only and does not replace professional veterinary advice. Always consult your veterinarian before starting, stopping, or changing any medication for your dog. Individual patient needs vary based on health status, concurrent conditions, and regional parasite risk. For the most current prescribing information, refer to the Credelio product label or the Merck Veterinary Manual.
Robin Maitland
All our authors care for dogs every day — read more of their work on the authors page.
