Olsalazine
5-aminosalicylic acid dimer
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| All uses (Management of colitis) | 10-20 mg/kg | PO | q12h | — | 🌍 EU |
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Olsalazine is a dimer of 5-aminosalicylic acid (5-ASA) used primarily for the management of colitis, particularly in patients who are sensitive to sulfasalazine.
Clinical Warning: Although the incidence of keratoconjunctivitis sicca (KCS) is much lower than with sulfasalazine, it remains a potential risk. Periodic Schirmer tear tests should be performed during therapy.
Mechanism of action
Olsalazine is a prodrug that is cleaved by colonic bacteria → releases free 5-ASA → exerts a local anti-inflammatory effect directly on the colonic mucosa.
Safety & warnings
Contraindications
- Patients sensitive to salicylates
Adverse effects
- Keratoconjunctivitis sicca (dry eye)
Precautions
Normal precautions should be observed. Monitor tear production periodically due to the risk of keratoconjunctivitis sicca.
Drug interactions
Activity will be potentiated by administration of other NSAIDs
Monitoring
- Schirmer tear tests (periodic)
- Clinical response (resolution of colitis signs)
Pharmacokinetics
Absorption
Acts locally in the colon after cleavage.
Metabolism
Cleaved by colonic bacteria into free 5-aminosalicylic acid (5-ASA).
Overdose
No specific information available. Overdose may exacerbate gastrointestinal signs or increase the risk of salicylate toxicity.
Available products
Formulations
- 250 mg capsule
- 500 mg tablet
Human-labeled
- 250 mg capsule
- 500 mg tablet
Regulatory status
Human authorized product used off-label under the cascade.
POM (Prescription Only Medicine). Human authorized product used off-label.
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store at room temperature. Normal precautions apply.
Client information
Administer this medication exactly as directed by your veterinarian. Do not give your pet any other pain relief or anti-inflammatory medications (like NSAIDs) without consulting your vet. Watch your pet's eyes closely; if you notice squinting, redness, or thick eye discharge, contact your veterinarian immediately as this drug can occasionally cause 'dry eye'.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.