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One selection filters the source overview, clinical facts, reports and dose calculator. Literature references are not species-filtered.
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Source overview
Recorded excerpts for one species. Each dose remains a separate source entry; no regimen is selected.
Choose one species to view its source overview. All-species evidence remains available below.
View full clinical evidence and sources ↓Clinical evidence
Pending clinical review (PROPOSED)Rule-based (RULE_BASED)— applies to the facts and dose entries in this species selection; individual source records retain their own status.
Indications2
Immune-mediated disease alternative to azathioprine/mycophenolate: IMHA/ITP (Evans), myasthenia gravis, polymyositis/polyarthritis (3–4 mg/kg response in polyarthritis series) — anecdotal/retrospective evidence tier
DogExtra-label (EXTRA_LABEL)1 source record · View provenance
- Dog · Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 437–438 — Indications table · Not applicable · Extra-label (EXTRA_LABEL) · Pending clinical review (PROPOSED) · Rule-based
Original excerpt: Immune-mediated disease alternative to azathioprine/mycophenolate: IMHA/ITP (Evans), myasthenia gravis, polymyositis/polyarthritis (3–4 mg/kg response in polyarthritis series) — anecdotal/retrospective evidence tier — Extra-label (human drug)
- Dog · Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 437–438 — Indications table · Not applicable · Extra-label (EXTRA_LABEL) · Pending clinical review (PROPOSED) · Rule-based
Immune-mediated disease (limited use; PK favorable — complete absorption, 60 h t½)
CatExtra-label (EXTRA_LABEL)1 source record · View provenance
- Cat · Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 437–438 — Indications table · Not applicable · Extra-label (EXTRA_LABEL) · Pending clinical review (PROPOSED) · Rule-based
Original excerpt: Immune-mediated disease (limited use; PK favorable — complete absorption, 60 h t½) — Extra-label
- Cat · Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 437–438 — Indications table · Not applicable · Extra-label (EXTRA_LABEL) · Pending clinical review (PROPOSED) · Rule-based
Dose regimens2
This calculator performs arithmetic only on the sourced dosing field shown for each result — it does not verify the field's accuracy, does not select which field to use for a patient, and does not replace a veterinarian's order. Not for clinical use. Confirm every result against the primary source before dispensing.
Choose one species above to view its dose calculator.
Adverse effects103
GI (inappetence, diarrhea) — dose-related — Most common → start low, titrate up
DogNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Dog · Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 437–438 — Side Effects / Adverse Effects table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Mild anemia, lethargy — Observed
DogNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Dog · Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 437–438 — Side Effects / Adverse Effects table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Human: hepatotoxicity, hypertension, marrow suppression — Class monitoring
Other speciesNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Other species · Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 437–438 — Side Effects / Adverse Effects table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
These are counts of spontaneously reported events, not proven adverse effects, causal relationships, or incidence rates.
Bars compare report counts within each species; they do not show incidence.
More reportsFewer reportsDog
- Vomiting6 reports
- Anaemia NOS5 reports
- Lethargy (see also Central nervous system depression in 'Neurological')5 reports
- Anorexia4 reports
- Diarrhoea4 reports
- Death by euthanasia3 reports
- Leucocytosis NOS3 reports
- Medication error NOS3 reports
- Thrombocytopenia3 reports
- Weight loss3 reports
- Abnormal ultrasound finding2 reports
- Behavioural disorder NOS2 reports
Monitoring1
Clinical: CBC (anemia), liver values, GI tolerance; metabolite levels where available; taper-response tracking
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 437–438 — Monitoring Parameters · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Contraindications1
Pregnancy
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 437–438 — Contraindications & Warnings table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Precautions4
Hepatic impairment; combine-with-care in multi-drug immunosuppression
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 437–438 — Contraindications & Warnings table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
The immunology triangle for exam day: azathioprine (purines) vs leflunomide (pyrimidines) vs cyclosporine (calcineurin) — three different biochemical bottlenecks, one clinical goal.
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 437–438 — Clinical pearl · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Species PK flip: humans need loading doses (2-week t½); dogs don't (day-long t½, 5-day steady state) — the reason human regimens don't transplant directly.
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 437–438 — Clinical pearl · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Evidence honesty: compelling anecdotes, no controlled trials — its niche is the azathioprine-intolerant or refractory patient.
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 437–438 — Clinical pearl · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Interactions3
Other immunosuppressives — Addative (deliberate steroid-sparing combinations)
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 437–438 — Drug Interactions table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
CYP/BCRP substrates (human — rosuvastatin class) — Metabolite-mediated interactions
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 437–438 — Drug Interactions table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Live vaccines — Avoid
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 437–438 — Drug Interactions table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Pharmacokinetics4
Mechanism — Prodrug → teriflunomide inhibits dihydroorotate dehydrogenase → blocks de novo pyrimidine synthesis (activated lymphocytes depend on it) + anti-inflammatory cytokine inhibition
Other speciesNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Other species · Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 437–438 — Pharmacokinetics table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Dog PK — t½ only 21–25 h (vs 2 WEEKS human) — no loading dose needed; steady state ~5 days
Other speciesNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Other species · Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 437–438 — Pharmacokinetics table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Cat PK — Complete oral absorption; t½ 60 h
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 437–438 — Pharmacokinetics table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Monitoring — Measure the METABOLITE (A77 1726), not parent
Other speciesNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Other species · Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 437–438 — Pharmacokinetics table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Pregnancy / lactation considerations1
Contraindicated in pregnancy (human teratogen; long human half-life = washout protocols/cholestyramine before conception — class rule).
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 437–438 — Pregnancy & Lactation · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Literature references17
References are linked to this drug. Species applicability is not recorded here, so the species filter does not narrow this list. Imported dates do not retain their original precision; confirm dates in the original citation.
- Case Report: Complete MRI-confirmed remission of presumptive meningoencephalitis of unknown origin in a Chihuahua using a steroid-free combination of leflunomide and mycophenolate mofetil.
Study summary not available in the imported record. Open the original citation to review the study.
- Retrospective evaluation of leflunomide as second-line immunosuppressive therapy in dogs with meningoencephalomyelitis of unknown origin: 18 cases (2018-2025).
Study summary not available in the imported record. Open the original citation to review the study.
- Cutaneous and mucosal ulceration associated with the use of leflunomide in three dogs.
Study summary not available in the imported record. Open the original citation to review the study.
- Dopamine agonist pramipexole halts leflunomide nephrotoxicity: A dual strike on TLR4-Driven inflammation and PI3K/Akt suppression.
Study summary not available in the imported record. Open the original citation to review the study.
- Acquired Myasthenia Gravis in a Juvenile Australian Shepherd Dog and Efficacy of Leflunomide Treatment.
Study summary not available in the imported record. Open the original citation to review the study.
Sources: PubMed, National Library of Medicine; openFDA, U.S. Food and Drug Administration; Papich MG. Saunders Handbook of Veterinary Drugs. 4th ed. Saunders; 2015.
Owner information handout
Plain-language medication information to review with the owner. Open the handout to print it or download a PDF.