PASER
Clinical safety rating
cautionComprehensive clinical and safety monograph for PASER (PASER).
Comprehensive clinical and safety monograph for PASER (PASER).
Treatment of tuberculosis in combination with other antituberculosis drugsOff-label: None
Inhibits cell wall synthesis in Mycobacterium tuberculosis by blocking mycolic acid synthesis. Also acts as a competitive inhibitor of folate synthesis.
| Metabolism | Hepatic via N-acetyltransferase (polymorphic acetylation); major metabolite is acetyl-PAS. |
| Excretion | Renal excretion accounts for approximately 80% of the administered dose, with about 60-70% as unchanged drug and 10-20% as metabolites (primarily acetylated). The remainder is excreted via feces (approximately 10-15%) and minor biliary elimination. Renal clearance is highly dependent on glomerular filtration rate. |
| Half-life | Terminal elimination half-life is 1.5 to 2.5 hours in patients with normal renal function. In anuria or severe renal impairment (CrCl <10 mL/min), half-life may extend to 8-12 hours. Clinical context: Accumulation occurs with renal failure, requiring dose adjustment. |
| Protein binding | Protein binding is approximately 10-15%, primarily to albumin. Binding is low, nonlinear, and saturable at high concentrations. |
| Volume of Distribution | Volume of distribution is 0.5-0.7 L/kg, indicating distribution into total body water. Clinical meaning: Moderate distribution suggests penetration into well-perfused tissues but limited CNS penetration unless inflamed. |
| Bioavailability | Oral bioavailability is approximately 70-80% (range 60-90%). Food decreases the rate and extent of absorption, with AUC reduction of about 20-40%. |
| Onset of Action | Oral: Clinical antimycobacterial effect begins within 2-4 hours after administration, corresponding to peak serum concentrations. Time to detectable bacteriostatic activity in sputum is approximately 2-3 days. |
| Duration of Action | Bacteriostatic effect persists for approximately 6-8 hours post-dose, necessitating twice-daily dosing. Duration is extended in renal impairment. |
| Molecular Weight | 153.14 |
4 g (8 capsules of 500 mg) orally every 8 hours, taken with food or an acidic beverage (e.g., orange juice) to enhance absorption.
| Dosage form | GRANULE, DELAYED RELEASE |
| Renal impairment | Contraindicated in severe renal impairment (CrCl <30 mL/min). For CrCl 30-50 mL/min: reduce dose to 4 g orally every 12 hours; monitor serum concentrations. Use with caution in moderate impairment. |
| Liver impairment | No specific dose adjustment guidelines for Child-Pugh classification. Use with caution in severe hepatic impairment due to potential hepatotoxicity; monitor liver function tests. |
| Pediatric use | Not recommended for children (safety and efficacy not established). |
| Geriatric use | Lower initial doses may be considered due to age-related decline in renal function. Monitor renal function and serum concentrations closely. |
| 1st trimester | Aminosalicylic acid (PASER) is generally avoided in first trimester unless benefit outweighs risk; animal studies show no teratogenicity but human data limited. |
| 2nd trimester | Use with caution; no known fetal harm, but monitor for maternal gastrointestinal effects. |
| 3rd trimester | Considered relatively safe; monitor for maternal hypokalemia and thyroid dysfunction. |
Clinical note
Comprehensive clinical and safety monograph for PASER (PASER).
| Placental transfer | Crosses placenta; fetal serum concentrations may reach maternal levels. |
| Breastfeeding | Excreted into breast milk in small amounts; unlikely to cause adverse effects in infant; monitor infant for diarrhea and rash. |
| Lactation Rating | L2 (probably compatible) |
| Teratogenic Risk | PASER (aminosalicylic acid) is classified FDA pregnancy category C. First trimester: Limited human data; animal studies show no teratogenicity but some fetal toxicity at high doses. Second and third trimesters: No known major malformations; risks may include gastrointestinal intolerance in mother. Advised use only if clearly needed. |
| Fetal Monitoring | Monitor maternal liver function, renal function, and gastrointestinal tolerance. Fetal monitoring not typically required; evaluate growth and well-being if prolonged use. |
| Fertility Effects | No known significant impact on fertility in humans. Animal studies show no impairment of fertility at therapeutic doses. |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to aminosalicylic acidSevere renal impairmentSevere hepatic impairment
| Precautions | May cause hypothyroidism, hepatitis, and crystalluria. Use with caution in patients with renal impairment or glucose-6-phosphate dehydrogenase deficiency. |
| Food/Dietary | Take with food to reduce gastrointestinal irritation. Avoid high-fat meals as they may delay absorption. Avoid alcohol. |
| Clinical Pearls | PASER (aminosalicylic acid) is a second-line antitubercular agent that inhibits folic acid synthesis. Administer with food to reduce GI upset; avoid concurrent use with salicylates due to additive GI irritation. Monitor for hepatotoxicity and hypersensitivity reactions. Drug levels should be monitored in patients with renal impairment. |
| Patient Advice | Take this medication with food to minimize stomach upset. · Do not crush or chew the tablets; swallow them whole. · Complete the full course of therapy even if you feel better. · Report any signs of liver problems (yellowing of skin/eyes, dark urine) or allergic reactions (rash, fever) immediately. · Avoid alcohol during treatment. · Store at room temperature away from moisture and heat. |
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