Para-aminosalicylic acid (4-Aminosalicylic acid)

Indications

Para-aminosalicylic acid (4-Aminosalicylic acid) is used for: Tuberculosis, Crohn's disease, Ulcerative colitis

Adult Dose

Oral Tuberculosis Adult: 150 mg/kg/day in 3-4 equally divided doses Crohn's disease Adult: 1.5 g/day (unlabelled use). Rectal Ulcerative colitis Adult: 2 g once a day as an enema in patients who are intolerant to sulphasalazine.

Child Dose

Oral Tuberculosis Child: 200-300 mg/kg/day (max: 10 mg) in 3-4 equally divided doses.

Renal Dose

Oral Tuberculosis Renal impairment: Haemodialysis: Administer dose afterwards and give 50% dose. Continuous arteriovenous haemofiltration: give 50% dose. CrCl (ml/min) Dosage Recommendation 10-50 50-75% dose. <10 50% dose. Crohn's disease Adult: 1.5 g/day (unlabelled use). Renal impairment: Haemodialysis: Administer dose afterwards and give 50% dose. Continuous arteriovenous haemofiltration: give 50% dose. CrCl (ml/min) Dosage Recommendation 10-50 50-75% dose. <10 50% dose. Rectal Ulcerative colitis Renal impairment: Haemodialysis: Administer dose afterwards and give 50% dose. Continuous arteriovenous haemofiltration: give 50% dose. CrCl (ml/min) Dosage Recommendation 10-50 50-75% dose. <10 50% dose.

Administration

Take with acidic food (e.g. apple sauce, yoghurt, orange juice).

Contra Indications

Hypersensitivity, severe renal disease, G6PD deficiency

Precautions

Renal and hepatic impairment, sodium salt in heart failure; gastric ulcer. Monitor patient closely for 1st 3 mth of treatment and counsel to report: sore throat, fever, unusual bleeding or bruising, persistent nausea or vomiting, or abdominal pain, Pregnancy, lactation

Pregnancy-Lactation

Interactions

May decrease absorption of digoxin and vitamin B12; additive adverse effects of aminosalicylates and salicylates; probenecid may increase toxicity by delaying renal excretion and enhancing plasma concentrations of aminosalicylate; activity of aminosalicylic acid may be antagonised by ester-type local anaesthetics such as procaine; may enhance effect of oral anticoagulants (may need to adjust dose); ammonium chloride may increase risk of crystalluria (do not use concurrently).

Adverse Effects

Side effects of Para-aminosalicylic acid (4-Aminosalicylic acid) : Nausea, vomiting, diarrhoea, abdominal pain; thyroid goitre, hypoglycaemia; pericarditis, vasculitis; encephalopathy, fever, skin eruptions, agranulocytosis, haemolytic anaemia, leucopenia, thrombocytopenia, hepatitis, jaundice, optic neuritis, eosinophilic pneumonia.

Mechanism of Action

Para-aminosalicylic acid (also known as aminosalicyclic acid) is bacteriostatic and active against M. tuberculosis. Other mycobacteria are usually resistant. It prevents plate biosynthesis in sensitive organisms. It has a relatively weak action compared with other anti-TB drugs and resistance may develop quickly if it is used alone, however it is still sometimes used in multi-drug resistant tuberculosis in combination with other anti-TB drugs.