VPT 311: General and Systemic Veterinary Pharmacology (2+1)

ANTISECRETORY DRUGS

• Sulfasalazine ( Salicylazosulfapyridine) it is a compound of 5-aminosalycylic acid (5-ASA) with sulfapyridine linked through an azo bond.
• The 5-ASA is of low solubility and it is poorly absorbed from the ileum.
• The azo bond is split by colonic bacteia to release 5-ASA and sulfapyridine.
• The former exerts a local anti-inflammatory effect, probably by inhibiting prostaglandin synthesis (and other mediators like leukotrienes, PAF as well as migration of inflammatory cells into bowl wall), decreases mucosal secretion affords considerable relief in ulcerative colitis and related inflammatory bowel disease.
• Given during an exacerbation it reduces number of stools, abdominal cramps and fever but is less effective than corticosteroids: may be employed for mild to moderate exacerbation.
• The beneficial effect of sulfasalazine is clearly not due to any antibacterial action ( bowel flora remains largely unaffected) sulpyridine moiety only serves to carry 5-ASA to the the colon without being absorbed proximally.
• However, part of the released sulfapyridine is absorbed in the colon and is responsible for adverse effects like rashes, fever, joint pain, haemolysis and blood dyscrasias.
• Nausea, vomiting, headache and anemia are other frequent side effects. Male infertility is reported.
• Sulfasalazine has also been used as a disease modifying drug in rheumatoid arthritis the absorbed sulfapyridine appears to be responsible for the therapeutic effect.