PBZ
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PBZ (PBZ).
PBZ (phenylbutazone) is a nonsteroidal anti-inflammatory drug (NSAID) that inhibits cyclooxygenase (COX) enzymes, reducing prostaglandin synthesis. It also has uricosuric effects.
| Metabolism | Primarily hepatic via CYP450 enzymes (including CYP2C9), with renal excretion of metabolites. |
| Excretion | Renal excretion of unchanged drug (approximately 70-80%) with the remainder as metabolites. Biliary/fecal excretion accounts for <5%. |
| Half-life | Terminal elimination half-life: 8-12 hours in adults; prolonged in renal impairment (up to 24 hours). |
| Protein binding | 95-98% bound to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 2-3 L/kg, indicating extensive tissue distribution. |
| Bioavailability | Oral: 60-70% (first-pass metabolism reduces absolute bioavailability). |
| Onset of Action | Oral: 30-60 minutes; Intravenous: 1-2 minutes; Intramuscular: 15-30 minutes. |
| Duration of Action | 4-6 hours after single dose; may extend up to 8 hours with higher doses or in hepatic impairment. |
25-50 mg orally every 4-6 hours as needed; not to exceed 300 mg/day. For severe allergies: 25 mg intramuscularly or intravenously every 4-6 hours.
| Dosage form | TABLET |
| Renal impairment | No specific guidelines available; use with caution in severe renal impairment (GFR <10 mL/min) due to potential accumulation. Consider dose reduction or increased dosing interval. |
| Liver impairment | Child-Pugh Class A: no adjustment; Child-Pugh Class B: reduce dose by 50% and monitor for sedation; Child-Pugh Class C: avoid use due to risk of hepatic encephalopathy or reduce dose by 75%. |
| Pediatric use | Children 2-6 years: 5 mg orally every 4-6 hours, not to exceed 30 mg/day; Children 6-12 years: 10-15 mg orally every 4-6 hours, not to exceed 60 mg/day; Children >12 years: adult dose. |
| Geriatric use | Start at 10 mg orally every 6-8 hours; titrate cautiously due to increased sensitivity (sedation, dizziness, anticholinergic effects). Avoid if possible; consider alternative antihistamine with lower anticholinergic burden. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PBZ (PBZ).
| Breastfeeding | PBZ is excreted into breast milk in low concentrations. The milk-to-plasma ratio is approximately 0.01-0.2. Due to potential adverse effects on infant cardiovascular and renal systems (e.g., platelet dysfunction, renal impairment), use is generally not recommended. Consider alternative analgesics with more established safety profiles. |
| Teratogenic Risk | PBZ (Piroxicam) is a nonsteroidal anti-inflammatory drug (NSAID). First trimester: Avoid use; associated with increased risk of miscarriage and congenital malformations (e.g., cardiac defects) due to prostaglandin synthesis inhibition. Second trimester: Use only if clearly needed; potential for oligohydramnios and fetal renal dysfunction. Third trimester: Contraindicated; risk of premature closure of ductus arteriosus, persistent pulmonary hypertension, and oligohydramnios. |
■ FDA Black Box Warning
Risk of serious gastrointestinal adverse events including bleeding, ulceration, and perforation; risk of cardiovascular thrombotic events; use is contraindicated for perioperative pain in CABG surgery.
| Serious Effects |
History of hypersensitivity to NSAIDs; active GI bleeding or peptic ulcer disease; severe hepatic or renal impairment; known coronary artery bypass graft (CABG) surgery; blood dyscrasias.
| Precautions | Risk of agranulocytosis, aplastic anemia, and other blood dyscrasias; GI toxicity; cardiovascular events; renal toxicity; hepatic effects; use only when other NSAIDs are ineffective and for short durations; contraindicated in patients with aspirin-sensitive asthma. |
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| Fetal Monitoring | Monitor maternal renal function, blood pressure, and signs of bleeding. Perform fetal ultrasound to assess amniotic fluid volume if used for prolonged periods. Monitor for oligohydramnios and ductus arteriosus constriction in the third trimester. |
| Fertility Effects | PBX may impair female fertility by inhibiting prostaglandin synthesis, affecting ovulation and implantation. This effect is reversible upon discontinuation. Use in women attempting to conceive is not recommended. |