Dog Medication Calculator: Safe Dosage Charts
Calculate safe medication doses for your dog by weight. Includes common OTC drugs with vet-reviewed dose ranges and important safety warnings.
Use CalculatorChoose dog or cat first, then enter the details that match your pet's species, weight, routine, and current situation.
Plumb's Veterinary Drugs is the definitive clinical pharmacology reference in veterinary medicine, used by veterinary professionals worldwide. The drug interaction checker component of Plumb's helps identify known and potential adverse interactions between drugs that may be prescribed concurrently in a patient receiving polypharmacy - multiple medications simultaneously. Multi-drug regimens are common in senior pets and pets with complex conditions, making drug interaction awareness a critical component of veterinary care. This guide covers the most clinically significant drug interactions in small animal medicine.
High-Risk Drug Interactions in Dogs and Cats
Use the table below to compare High-Risk Drug Interactions in Dogs and Cats.
| Drug A | Drug B | Interaction Type | Clinical Effect | Management |
|---|---|---|---|---|
| NSAIDs (carprofen, meloxicam, etc.) | Corticosteroids (prednisone, dexamethasone) | High risk - GI/renal toxicity | Combined use dramatically increases GI ulceration and bleeding risk; renal injury | AVOID concurrent use; washout period required between drugs |
| NSAIDs | Other NSAIDs (any two NSAIDs) | High risk - additive GI toxicity | GI hemorrhage risk significantly increased | Never combine two NSAIDs; minimum 7-day washout between switches |
| Selegiline (Anipryl) | Tramadol or meperidine | High risk - serotonin syndrome | Potentially fatal serotonin toxicity | Contraindicated; 14-day washout before starting either drug |
| Selegiline | SSRIs (fluoxetine, sertraline) | High risk - serotonin syndrome | Serotonin toxicity risk | Contraindicated combination |
| Digoxin | Furosemide | Moderate - hypokalemia potentiates digoxin toxicity | Hypokalemia from furosemide increases digoxin toxicity risk | Monitor serum potassium and digoxin levels closely |
| Phenobarbital | Chloramphenicol | Moderate - enzyme inhibition | Chloramphenicol inhibits phenobarbital metabolism; increased phenobarbital toxicity | Monitor phenobarbital levels if chloramphenicol added |
| Metronidazole | Phenobarbital | Moderate - enzyme induction | Phenobarbital induces metronidazole metabolism; reduced metronidazole efficacy | May need higher metronidazole dose |
| Potassium bromide | High-sodium diet or saline IV | Moderate - competition | Sodium competes with bromide reabsorption; reduced KBr levels, breakthrough seizures | Maintain consistent dietary sodium; avoid high-sodium IV fluids |
MDR1-Mediated Drug Interactions
Dogs with the MDR1 (ABCB1) gene mutation have dramatically reduced ability to pump certain drugs out of the CNS, leading to dangerous drug accumulation in the brain. Affected breeds (Collies, Australian Shepherds, Shelties, Border Collies, others) must be screened before use of any MDR1-substrate drug.
| Drug | Risk in MDR1 Mutant Dogs | Alternative |
|---|---|---|
| Ivermectin (anti-parasitic doses) | Fatal CNS toxicity at doses safe in normal dogs | Use milbemycin at appropriate doses |
| Loperamide (Imodium) | CNS depression, respiratory depression | Avoid; use metronidazole or dietary management |
| Acepromazine | Profound sedation at normal doses | Use lower doses; or choose alternative pre-anesthetic |
| Vincristine (chemotherapy) | Increased toxicity | Use with extreme caution; dose reduction may be needed |
| Cyclosporine | Variable increased exposure | Monitor drug levels more closely |
Key Drug Monitoring Requirements
Use the table below to compare Key Drug Monitoring Requirements.
| Drug | Monitoring Test | Frequency | Target Range / Action Threshold |
|---|---|---|---|
| Phenobarbital | Serum phenobarbital; liver function (ALT, ALP, bile acids) | At 2 weeks after start; then every 6 months | Serum level 20-40 mcg/mL; ALT elevation: reassess dose |
| Digoxin | Serum digoxin; electrolytes; renal function | At 7-10 days; then every 6 months | Serum level 0.8-2 ng/mL; toxicity above 2 ng/mL |
| Cyclosporine | Trough blood cyclosporine level | First 2 months monthly; then every 6 months | Target varies by indication; typically 200-400 ng/mL |
| NSAIDs (long-term) | Renal panel, liver enzymes, CBC | Baseline before starting; at 2 weeks; then every 6 months | Any rise in creatinine, BUN, or liver enzymes: reassess |
Frequently Asked Questions
Is Plumb's available to pet owners?
Plumb's Veterinary Drugs (plumbs.com) is a subscription-based platform primarily used by veterinary professionals. A basic free version allows limited drug searches. For drug interaction concerns, the best approach is to discuss all current medications at every veterinary visit, bring a complete medication list including supplements, and ask your vet specifically if there are any interactions to be aware of when a new drug is added.
What should I do if I think my pet is experiencing a drug reaction?
Contact your veterinarian immediately. Signs of drug reactions include sudden vomiting, diarrhea, facial swelling, difficulty breathing, collapse, excessive sedation, tremors, or changes in urination. Bring all medication containers to the vet appointment. The ASPCA Animal Poison Control Center (888-426-4435) is also available for drug toxicity guidance.
Note: Drug interaction results are informational and should be confirmed with a veterinarian or veterinary pharmacist before combining medications.
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