AMINOSALICYLIC ACID (PARA-AMINOSALICYLIC ACID)

AMINOSALICYLIC ACID (PARA-AMINOSALICYLIC ACID) (a-mee-noe-sal-i-sil'ik) Paser Classifications: antituberculosis agent; Therapeutic:antituberculosis agent Prototype: Isoniazid Pregnancy Category: C

Availability

4 g packets

Action

Aminosalicylic acid and salts are highly specific bacteriostatic agents that suppress growth and multiplication of Mycobacterium tuberculosis by preventing folic acid synthesis. Their mechanism of action resembles that of sulfonamides. Aminosalicylates also reportedly have potent hypolipemic action.

Therapeutic Effect

Aminosalicylates are an effective antiinfective alone or in combined therapy and reduce serum cholesterol and triglycerides by lowering LDL and VLDL.

Uses

With streptomycin or isoniazid or both in treatment of pulmonary and extrapulmonary tuberculosis to delay drug resistance.

Unlabeled Uses

Documented for lipid-lowering effect.

Contraindications

Hypersensitivity to aminosalicylates, salicylates, or to compounds containing para-aminophenyl groups (e.g., sulfonamides, certain hair dyes), G6PD deficiency, use of the sodium salt in patients on sodium restriction or CHF; pregnancy (category C); lactation.

Cautious Use

Impaired renal and hepatic function; blood dyscrasias; goiter; gastric ulcer.

Route & Dosage

Tuberculosis Adult: PO 10–12 g/d in 2–3 divided doses Child: PO 150–300 mg/kg/d in 3–4 divided doses

Administration

Oral

• Give with or immediately following meals to reduce irritative gastric effects. Physician may order an antacid to be given concomitantly. Generally, GI adverse effects disappear after a few days of therapy.
• Store in tight, light-resistant containers in a cool, dry place, preferably at 15°–30° C (59°–86° F), unless otherwise directed.

Adverse Effects (≥1%)

Body as a Whole: Fever, chills, generalized malaise, joint pain, rash, fixed-drug eruptions, pruritus; vasculitis; Loeffler's syndrome. CNS: Psychotic reactions. GI: Anorexia, nausea, vomiting, abdominal distress, diarrhea, peptic ulceration, acute hepatitis, malabsorption. Hematologic: Leukopenia, agranulocytosis, eosinophilia, lymphocytosis, thrombocytopenia, hemolytic anemia; (G6PD deficiency), prothrombinemia. Urogenital: Renal (irritation), crystalluria. Other: With long-term administration, goiter.

Diagnostic Test Interference

Aminosalicylates may interfere with urine urobilinogen determinations (using Ehrlich's reagent), and may cause false-positive urinary protein and VMA determinations (with diazoreagent); false-positive urine glucose may result with cupric sulfate tests, e.g., Benedict's solution, but reportedly not with glucose oxidase reagents (e.g., TesTape, Clinistix). Reduces serum cholesterol, and possibly serum potassium, serum PBI, and 24-hour I-131 thyroidal uptake (effect may last almost 14 d).

Interactions

Drug: Increases hypoprothrombinemic effects of oral anticoagulants; increased risk of crystalluria with ammonium chloride, ascorbic acid; decreased intestinal absorption of cyanocobalamin, folic acid, digoxin; antihistamines may inhibit PAS absorption; may increase or decrease phenytoin levels; probenecid, sulfinpyrazone decrease PAS elimination.

Pharmacokinetics

Absorption: Almost completely from GI tract; sodium form more rapidly absorbed than the acid. Peak: 1.5–2 h. Duration: 4 h. Distribution: Well distributed to tissue and body fluids except CSF unless meninges are inflamed. Metabolism: In liver. Elimination: >80% in urine in 7–10 h. Half-Life: 1 h.

Nursing Implications

Assessment & Drug Effects

• Monitor for abrupt onset of fever, particularly during the early weeks of therapy, and clinical picture resembling that of infectious mononucleosis (malaise, fatigue, generalized lymphadenopathy, splenomegaly, sore throat), as well as minor complaints of pruritus, joint pains, and headache, which strongly suggest hypersensitivity; report these symptoms promptly.
• Monitor I&O and encourage fluids. High concentrations of drug are excreted in urine, and this can cause crystalluria and hematuria.
• Note: To minimize crystalluria, keep urine neutral or alkaline with adjunctive drugs, such as antacids or with diet.

Patient & Family Education

• Rinse mouth with clear water or chew sugar-free gum or candy to relieve the mildly sour or bitter aftertaste of aminosalicylic acid.
• Note: Hypersensitivity reactions may occur after a few days, but most commonly in the fourth or fifth week; report promptly.
• Notify physician if sore throat or mouth, malaise, unusual fatigue, bleeding or bruising occurs (symptoms of blood dyscrasia).
• Note: Therapy generally lasts about 2 y. Adhere to the established drug regimen, and remain under close medical supervision to detect possible adverse drug effects during the treatment period. Resistant TB strains develop more rapidly when drug regimen is interrupted or is sporadic.
• Note: Urine may turn red on contact with bleach used in commercial toilet bowl cleaners.
• Do not take aspirin or other OTC drugs without physician's approval.
• Discard drug if it discolors (brownish or purplish); this signifies decomposition.

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Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug