{"hq_id":"hq-p-pet-000081","name":"Canine and Feline Dewormers (Pyrantel Pamoate, Fenbendazole, Praziquantel — Therapeutic Index, Drug Interactions, Off-Target Toxicity)","category":{"primary":"pet","secondary":"veterinary_medication","tags":["pyrantel pamoate","fenbendazole","praziquantel","dewormer","anthelmintic","tapeworm","roundworm","deworm","veterinary OTC","drug interaction"]},"product_tier":"PET","overall_risk_level":"low_to_moderate","description":"Canine and feline dewormers — pyrantel pamoate (Strongid, Nemex; OTC for dogs), fenbendazole (Panacur, Safe-Guard; OTC for dogs and many small-animal species), and praziquantel (Droncit, Drontal — Rx; tapeworm-specific) — are among the safest veterinary drug classes when used at label dose. Pyrantel acts as a nicotinic-receptor agonist on parasite neuromuscular junctions with very limited mammalian absorption, yielding therapeutic indices >100. Fenbendazole is a benzimidazole that disrupts parasite microtubule polymerization; mammalian therapeutic index is wide (>100x label in most species), but bone-marrow suppression has been reported in pigeons, vultures, reptiles, and rare canine idiosyncratic cases. Praziquantel disrupts cestode tegumental calcium homeostasis; LD50 in dogs/cats >2,000 mg/kg vs label 5 mg/kg. The principal household risk profile is therefore not direct toxicity but (a) mis-identification of parasite class — pyrantel does NOT kill tapeworms (cestodes); (b) ivermectin co-administration in MDR1-mutant collies/Aussies/Shelties producing sensitization to subsequent ML-class drugs; (c) fenbendazole-induced acute hepatic necrosis in vultures and other Old-World birds (relevant to mixed exotic-pet households); and (d) dose-scaling errors when using livestock-grade fenbendazole (10% paste = 100 mg/g) in small household pets, where a single mis-measured gram can deliver 10× the canine label dose.","synthesis":{"derived_risk_level":"negligible","synthesis_confidence":0.5,"synthesis_method":"compound_composition","context_used":"human_infant","context_source":"available_priority","exposure_modifier":0.85,"vulnerability_escalated":false,"escalation_reason":null,"compounds_resolved":4,"compounds_total":4,"synthesis_date":"2026-05-09","synthesis_version":"1.2.0","methodology_note":"exposure_modifier and adjusted_magnitude are computed from ALETHEIA-calibrated heuristics (route × duration × frequency multipliers, clamped to [0.5, 1.4]). Multipliers are directionally informed by EPA Exposure Factors Handbook (2011) and CalEPA OEHHA but are not regulatory consensus. See /api/methodology for full disclosure."},"hazard_summary":{"sensitive_populations":"MDR1-mutant herding breeds (ivermectin cross-class), exotic birds/reptiles (fenbendazole), puppies and kittens, debilitated animals","overall_risk":"low_to_moderate","primary_concerns":["Mis-identification of parasite class — pyrantel does not cover tapeworms","Livestock-grade fenbendazole paste dose-scaling errors in small pets","Fenbendazole bone-marrow suppression in Old-World birds and some reptiles","MDR1-mutant herding breeds and ivermectin cross-class confusion","Owner empirical deworming without fecal exam — selection pressure for resistance"],"exposure_routes":"Oral ingestion at label dose (very wide therapeutic index for the dewormer agents themselves)"},"exposure":{"routes":["oral"],"contact_types":["oral_direct"],"users":["pet_dog","pet_cat","pet_other"],"duration":"acute","frequency":"monthly","scenarios":["Routine quarterly deworming per CAPC guidelines (puppies/kittens at 2/4/6/8 weeks)","Owner uses pyrantel for assumed tapeworm — fails because pyrantel does not cover cestodes","Livestock-grade Safe-Guard 10% paste mis-dosed by gram in small dog (10× overdose)","Mixed-exotic household — fenbendazole given to pet pigeon/parrot causes bone-marrow suppression","MDR1-mutant collie given high-dose ivermectin (separate ML drug) — neurotoxicity"],"notes":"Pyrantel pamoate FDA-CVM OTC for dogs since 1972. Fenbendazole FDA-CVM OTC for dogs (50 mg/kg × 3 days). Praziquantel Rx — feline Drontal Plus, canine Droncit. MDR1 (ABCB1) mutation: ~70% of Collies, ~50% Australian Shepherds, ~15% Shelties; Washington State University VCPL provides commercial genetic testing. Ivermectin is NOT in standard dewormer products but is in heartworm preventives — cross-class confusion drives owner over-dosing. Fenbendazole avian/reptilian sensitivity: Old-World vultures (Aegypiidae) particularly affected; CAPC bird-specific dosing exists. Pyrantel does NOT cover tapeworms — owners assuming complete coverage frequently miss Dipylidium and Taenia infections (CAPC 2023 surveillance underscores parasite-class identification before therapy)."},"consumer_guidance":{"usage_warning":"Have a fecal exam performed before empirical deworming — not all parasites respond to all classes. Pyrantel does NOT cover tapeworms; praziquantel does. Use weight-appropriate consumer-pet formulations, NOT livestock paste — a small dosing error in 10% paste delivers 10× overdose. MDR1-test herding breeds (collies, Australian shepherds, Shelties) before any ivermectin/milbemycin/moxidectin product. Do not treat exotic birds or reptiles with off-label canine dewormer doses without exotic-animal veterinary supervision. Repeat dewormer per parasite life cycle (typical 14-21 days) to catch newly hatched larvae.","safer_alternatives":["Combination products (Drontal Plus) for broad-spectrum coverage in single dose","Fecal-PCR screening to identify parasite class before empirical therapy","Selamectin (Revolution) topical — covers heartworm, fleas, ticks, intestinal nematodes; safe in MDR1 mutants","Milbemycin (Sentinel, Interceptor Plus) — broad-spectrum, MDR1-safer than ivermectin","Prebiotic/probiotic GI support post-deworming (optional adjunct)"]},"regulatory":{"applicable_regulations":[{"jurisdiction":"USA","regulation":"FDA Center for Veterinary Medicine (CVM)","citation":"21 U.S.C. 360b; 21 CFR Parts 514, 530, 558","requirements":"New animal drugs require FDA-CVM approval (NADA/ANADA). Adverse Drug Experience (ADE) reporting under 21 CFR 514.80. Extralabel use governed by AMDUCA (1994) and 21 CFR 530.","compliance_status":null,"effective_date":null,"enforcing_agency":"FDA-CVM","penalties":null,"source_ref":null},{"jurisdiction":"USA","regulation":"AVMA Animal Poison Control reporting","citation":"Voluntary; ASPCA APCC + Pet Poison Helpline data referenced by FDA-CVM","requirements":"Veterinary professionals report adverse drug events to FDA-CVM Form 1932a; consumers report via 1-888-FDA-VETS or APCC.","compliance_status":null,"effective_date":null,"enforcing_agency":"AVMA / FDA-CVM","penalties":null,"source_ref":null},{"jurisdiction":"EU","regulation":"Veterinary Medicinal Products Regulation (EU) 2019/6","citation":"Regulation (EU) 2019/6 (effective 28 January 2022)","requirements":"Centralised authorisation for veterinary medicines via EMA. Pharmacovigilance reporting mandatory for marketing authorisation holders.","compliance_status":null,"effective_date":"2022-01-28","enforcing_agency":"EMA / national CAs","penalties":null,"source_ref":null}],"certifications":[],"labeling":{"required_disclosures":[],"prop65_warning":{"required":null,"chemicals":[],"endpoint":null,"notes":null},"ghs_labeling":{"required":null,"signal_word":null,"pictograms":[],"hazard_statements":[],"notes":null},"hidden_ingredients":{"trade_secret_protected":null,"categories_hidden":[],"estimated_count":null,"known_concerns":null,"notes":null},"notes":null},"recalls":[],"regulatory_gap":null,"notes":null},"lifecycle":{"recyclable":false,"disposal_guidance":"Unused dewormer suspension/tablets: return to veterinary clinic or DEA take-back. Livestock-grade paste tubes: regular waste once empty.","hazardous_waste":false,"expected_lifespan":"tablet 24-month shelf life; suspension 12 months once opened"},"formulation":{"form":"varies","key_ingredients":[],"certifications":[]},"materials":{"common":[],"concerning":[],"preferred":[]},"compound_composition":[{"hq_id":"hq-c-org-000559","compound_name":null,"role":"active_ingredient","typical_concentration":"pyrantel pamoate 50 mg/mL suspension; canine label 5 mg/kg single dose; very wide therapeutic index"},{"hq_id":"hq-c-org-002079","compound_name":null,"role":"active_ingredient","typical_concentration":"fenbendazole 10% paste / 222 mg granules; canine label 50 mg/kg/day × 3 days; reptile/bird sensitivity"},{"hq_id":"hq-c-org-000556","compound_name":null,"role":"active_ingredient","typical_concentration":"praziquantel 23-34 mg tablets; canine/feline label 5 mg/kg single dose; LD50 >2,000 mg/kg"},{"hq_id":"hq-c-org-000179","compound_name":null,"role":"co_administered_drug","typical_concentration":"ivermectin (separate product) — MDR1-mutant collie/Aussie/Sheltie sensitivity; not used in this product class but cross-class confusion risk"}],"identifiers":{"common_names":["canine and feline dewormers (pyrantel pamoate, fenbendazole, praziquantel — therapeutic index, drug interactions, off-target toxicity)"],"aliases":[],"manufacturer":null,"brands":[]},"brand_examples":[],"brand_examples_disclaimer":null,"sources":[{"type":"expert_curation","name":"ALETHEIA Safety Database","date":"2026-05-08"}],"meta":{"schema_version":"4.0.0","last_updated":"2026-05-08","timestamp":"2026-06-11T20:59:42.858Z"},"_notice":"ALETHEIA output is reference data, not professional advice. Not a substitute for primary agency sources or qualified professionals. See https://aletheia.holisticquality.io/disclaimer.","_disclaimer_url":"https://aletheia.holisticquality.io/disclaimer"}