Olsalazine is a prodrug composed of two molecules of 5-aminosalicylic acid (5-ASA) linked by an azo bond. The mechanism of action involves:

1. Targeted Delivery: Olsalazine remains intact until it reaches the colon, where bacterial enzymes cleave the azo bond, releasing the active 5-ASA directly at the site of inflammation.
2. Local Anti-inflammatory Effects: 5-ASA works topically in the colon to reduce inflammation by inhibiting the production of pro-inflammatory mediators such as prostaglandins and leukotrienes.
3. Antioxidant Properties: It scavenges free radicals, which contribute to tissue damage in ulcerative colitis.
4. Immunomodulation: 5-ASA may also modulate the immune response by inhibiting the activation of nuclear factor-kappa B (NF-κB), a key regulator of inflammation.

This targeted delivery minimizes systemic absorption and reduces the risk of side effects.

Olsalazine is primarily used for:

1. Ulcerative Colitis:
   • Treatment of mild to moderate active ulcerative colitis.
   • Maintenance of remission in ulcerative colitis.

It is particularly useful for patients who cannot tolerate other aminosalicylates like sulfasalazine due to side effects.

The dosage of olsalazine varies depending on the indication and patient response. Below are general guidelines:

1. Adults:
   • Active Ulcerative Colitis: 1 g (two 500 mg capsules) taken twice daily (total daily dose: 2 g).
   • Maintenance of Remission: 500 mg taken twice daily (total daily dose: 1 g).
2. Children:
   • Safety and efficacy in children have not been established.
3. Administration:
   • Olsalazine should be taken with food to minimize gastrointestinal side effects.
   • Swallow the capsules whole; do not crush or chew.

Olsalazine is generally well-tolerated, but some side effects may occur. These include:

1. Common Side Effects:
   • Diarrhea (often dose-related)
   • Abdominal pain
   • Nausea
   • Headache
2. Less Common Side Effects:
   • Vomiting
   • Rash
   • Joint pain
3. Rare but Serious Side Effects:
   • Hypersensitivity Reactions: Allergic reactions such as rash, fever, and anaphylaxis.
   • Hepatotoxicity: Elevated liver enzymes or hepatitis.
   • Renal Impairment: Rare cases of interstitial nephritis or kidney dysfunction.
   • Blood Disorders: Leukopenia, thrombocytopenia, or agranulocytosis.

1. Contraindications:
   • Hypersensitivity to olsalazine, salicylates, or any component of the formulation.
   • Severe renal or hepatic impairment.
2. Warnings:
   • Renal Function: Monitor renal function before and during treatment, especially in patients with pre-existing kidney disease.
   • Hepatic Function: Monitor liver function tests in patients with a history of liver disease.
   • Pregnancy and Lactation: Use with caution during pregnancy and breastfeeding. Consult a healthcare provider for risks and benefits.
3. Monitoring:
   • Regular monitoring of renal and hepatic function.
   • Watch for signs of hypersensitivity reactions or blood disorders.

Olsalazine has a low potential for drug interactions due to its localized action in the colon. However, the following should be considered:

1. Anticoagulants (e.g., warfarin): Olsalazine may increase the risk of bleeding due to its effect on platelet function.
2. Azathioprine or 6-Mercaptopurine: Concurrent use may increase the risk of blood disorders.
3. Non-Steroidal Anti-Inflammatory Drugs (NSAIDs): May increase the risk of nephrotoxicity.
4. Live Vaccines: Avoid administering live vaccines during olsalazine therapy due to potential immunosuppressive effects.

Olsalazine is available under its generic name as well as brand names. Some common formulations include:

• Generic Name: Olsalazine sodium
• Brand Names: Dipentum (commonly used in the UK and other regions).