PASER

Clinical safety rating: caution

Comprehensive clinical and safety monograph for PASER (PASER).

How it works

Inhibits cell wall synthesis in Mycobacterium tuberculosis by blocking mycolic acid synthesis. Also acts as a competitive inhibitor of folate synthesis.

What the body does with it

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.

Classification & Brands

Dosing & administration

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.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for PASER (PASER).

Breastfeeding	Excreted into breast milk in small amounts. M/P ratio unknown. Considered compatible with breastfeeding by American Academy of Pediatrics; monitor infant for diarrhea or rash.
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.

Warnings & precautions

■ FDA Black Box Warning

None

Side Effect Profile

Serious Effects

Absolute Contraindications

Hypersensitivity to para-aminosalicylic acid or any component; severe renal impairment.

Clinical Precautions

Precautions

May cause hypothyroidism, hepatitis, and crystalluria. Use with caution in patients with renal impairment or glucose-6-phosphate dehydrogenase deficiency.

Clinical Tips & Counseling

Drug interactions

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PASER

Clinical safety rating: caution

Comprehensive clinical and safety monograph for PASER (PASER).

How it works

Inhibits cell wall synthesis in Mycobacterium tuberculosis by blocking mycolic acid synthesis. Also acts as a competitive inhibitor of folate synthesis.

What the body does with it

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.

Classification & Brands

Dosing & administration

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.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for PASER (PASER).

Breastfeeding	Excreted into breast milk in small amounts. M/P ratio unknown. Considered compatible with breastfeeding by American Academy of Pediatrics; monitor infant for diarrhea or rash.
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.

Warnings & precautions

■ FDA Black Box Warning

None

Side Effect Profile

Serious Effects

Absolute Contraindications

Hypersensitivity to para-aminosalicylic acid or any component; severe renal impairment.

Clinical Precautions

Precautions

May cause hypothyroidism, hepatitis, and crystalluria. Use with caution in patients with renal impairment or glucose-6-phosphate dehydrogenase deficiency.

Clinical Tips & Counseling

Drug interactions

Loading safety data…