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. |
| Molecular Weight | 284.4 |
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 | Avoid during first trimester due to potential teratogenic effects; limited human data but animal studies show fetal abnormalities. |
| 2nd trimester | Use only if clearly needed; may cause fetal respiratory depression or other adverse effects. |
| 3rd trimester | Avoid near term due to risk of neonatal respiratory depression, withdrawal, or other adverse effects. |
Clinical note
Comprehensive clinical and safety monograph for PBZ (PBZ).
| Placental transfer | Crosses placenta readily; fetal concentrations may approach maternal levels. |
| Breastfeeding | Excreted into breast milk in small amounts; monitor infant for sedation, poor feeding, or respiratory depression. Use with caution, especially in neonates or preterm infants. |
| Lactation Rating |
■ 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 |
Hypersensitivity to PBZ or any componentAcute or chronic respiratory depressionSevere hepatic impairmentConcomitant use with MAO inhibitors (current or within 14 days)Narrow-angle glaucoma (uncontrolled)
| 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. |
| Food/Dietary | Avoid concurrent use of alcohol and other CNS depressants. No specific food restrictions, but grapefruit juice has not been studied with this drug. Administer with food if gastrointestinal discomfort occurs. |
Loading safety data…
| L3 - Moderately Safe (based on limited data, potential adverse effects). |
| 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. |
| 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. |
| Clinical Pearls | PBZ (tripelennamine) is a first-generation antihistamine with sedative properties. It is used primarily for allergic conditions and pruritus. Avoid in patients with narrow-angle glaucoma, prostatic hyperplasia, or urinary retention. Monitor for anticholinergic effects (dry mouth, blurred vision, constipation). May cause paradoxical excitation in children. Dose reduction needed in hepatic impairment. |
| Patient Advice | Do not drive or operate heavy machinery until you know how this medication affects you, as it may cause drowsiness. · Avoid alcohol and other CNS depressants to prevent increased sedation. · Take with food or milk to reduce stomach upset. · Do not crush or chew extended-release tablets; swallow whole. · Contact your doctor if you experience blurred vision, difficulty urinating, or severe constipation. · May cause dry mouth; use sugar-free gum or candy to alleviate. · Store at room temperature away from moisture and heat. · Keep out of reach of children; overdose may cause hallucinations or seizures. |