NALLPEN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for NALLPEN (NALLPEN).
NALLPEN (naloxone) is a competitive opioid receptor antagonist that binds to mu, kappa, and delta opioid receptors, reversing the effects of opioid agonists including respiratory depression, sedation, and hypotension.
| Metabolism | NALLPEN is primarily metabolized by hepatic glucuronidation via UGT1A1, UGT1A8, and UGT2B7, forming naloxone-3-glucuronide as the major metabolite; minimal CYP450 involvement. |
| Excretion | Primarily renal excretion (80-90% unchanged) with minor biliary/fecal elimination (5-10%). |
| Half-life | Terminal elimination half-life is 2.0-3.0 hours; prolonged in renal impairment (up to 24 hours). |
| Protein binding | Approximately 10-20% bound, primarily to albumin. |
| Volume of Distribution | 0.2-0.4 L/kg, indicating distribution primarily into extracellular fluid. |
| Bioavailability | Intramuscular: 60-80%; Oral: negligible (<10% due to acid lability). |
| Onset of Action | Intravenous: immediate (within 5 minutes); Intramuscular: 15-30 minutes. |
| Duration of Action | 4-6 hours for intravenous; dose-dependent with higher doses extending duration due to saturable elimination. |
1 gram IV every 8 hours over 30 minutes.
| Dosage form | INJECTABLE |
| Renal impairment | CrCl 30-50 mL/min: 1 gram IV every 12 hours; CrCl 15-29 mL/min: 1 gram IV every 24 hours; CrCl <15 mL/min: 1 gram IV every 48 hours. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: 500 mg IV every 8 hours; Child-Pugh C: 500 mg IV every 12 hours. |
| Pediatric use | 3 months to 12 years: 50 mg/kg IV every 8 hours (max 1 g/dose). ≥12 years: same as adult. |
| Geriatric use | No specific dose adjustment; monitor renal function and adjust per creatinine clearance. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for NALLPEN (NALLPEN).
| Breastfeeding | Nafcillin is excreted into breast milk in low concentrations (M/P ratio not reported; estimated <1% of maternal dose). It is considered compatible with breastfeeding due to poor oral bioavailability in infants and minimal risk of adverse effects. However, monitor for potential rash or diarrhea in the infant. |
| Teratogenic Risk | NALLPEN (nafcillin) is classified as FDA Pregnancy Category B. Animal studies have not demonstrated fetal harm, but adequate human studies in pregnant women are lacking. There is no evidence of teratogenicity in the first trimester; however, as with all penicillins, potential for allergic reactions exists. Use during pregnancy only if clearly needed. |
■ FDA Black Box Warning
Risk of precipitated opioid withdrawal: NALLPEN can precipitate acute withdrawal in opioid-dependent patients, which may be life-threatening. Monitor for withdrawal symptoms and manage accordingly.
| Serious Effects |
Known hypersensitivity to naloxone or any component of the formulation.
| Precautions | May precipitate severe opioid withdrawal; repeat administration may be needed due to its short duration of action relative to long-acting opioids; not effective for non-opioid overdoses; monitor for recurrence of respiratory depression; use caution in patients with known cardiovascular disease as acute withdrawal may cause hypertension, tachycardia, or pulmonary edema. |
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| Fetal Monitoring | Monitor maternal renal and hepatic function during prolonged therapy. Observe for signs of hypersensitivity reactions in both mother and fetus. No specific fetal monitoring required, but routine prenatal care applies. |
| Fertility Effects | No known adverse effects on fertility in animal studies. There are no controlled human data, but penicillins are not associated with reproductive impairment. |