TENSILON PRESERVATIVE FREE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TENSILON PRESERVATIVE FREE (TENSILON PRESERVATIVE FREE).
Edrophonium chloride is a reversible acetylcholinesterase inhibitor. It binds to the anionic site of acetylcholinesterase, preventing hydrolysis of acetylcholine and thereby increasing acetylcholine concentrations at the neuromuscular junction and in the autonomic nervous system.
| Metabolism | Primarily eliminated unchanged via renal excretion; minor hepatic ester hydrolysis. |
| Excretion | Primarily renal excretion as unchanged drug and metabolites; approximately 80-90% excreted in urine within 24 hours, with about 30% as unchanged edrophonium. Biliary/fecal elimination accounts for <10%. |
| Half-life | Terminal elimination half-life is approximately 1.5-2 hours in patients with normal renal function. In renal impairment, half-life may be prolonged (up to 8-10 hours in severe renal failure), necessitating dose adjustment. |
| Protein binding | Approximately 25-30% bound primarily to albumin. |
| Volume of Distribution | Volume of distribution (Vd) is approximately 0.5-1.0 L/kg, indicating distribution into extracellular fluid and tissues. |
| Bioavailability | Intravenous: 100% (bioavailability is complete for IV administration). Intramuscular and subcutaneous routes have variable absorption; bioavailability is considered high but not precisely quantified; oral bioavailability is negligible (<5%) due to extensive first-pass metabolism and poor absorption, thus not used clinically. |
| Onset of Action | Intravenous: 30-60 seconds; Intramuscular: 2-10 minutes; Subcutaneous: 2-10 minutes. |
| Duration of Action | Intravenous: 5-15 minutes (peak effect at 1-2 minutes); Intramuscular: 20-40 minutes; Subcutaneous: 20-40 minutes. Duration is dose-dependent and shorter in myasthenia gravis patients. |
2 mg intravenous test dose; if tolerated, 8 mg IV push over 1-2 minutes. Diagnostic dose may be repeated after 1 hour.
| Dosage form | INJECTABLE |
| Renal impairment | No specific dose adjustment guidelines; use with caution in severe renal impairment (CrCl <30 mL/min) due to potential accumulation. |
| Liver impairment | No specific Child-Pugh based adjustments; caution in severe hepatic impairment due to reduced clearance. |
| Pediatric use | 0.04 mg/kg IV test dose; if tolerated, 0.15 mg/kg IV push, not to exceed 10 mg total. |
| Geriatric use | Initiate at lower end of dosing range (e.g., 2 mg test dose) due to increased sensitivity and reduced renal function; monitor closely for cholinergic adverse effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for TENSILON PRESERVATIVE FREE (TENSILON PRESERVATIVE FREE).
| Breastfeeding | Unknown if edrophonium is excreted in human milk; M/P ratio not available. Use with caution in nursing mothers due to potential for infant cholinergic effects (e.g., diarrhea, increased secretions). |
| Teratogenic Risk | Pregnancy Category C. Edrophonium chloride crosses the placenta. First trimester: Limited human data; animal studies show no teratogenicity at clinical doses. Second and third trimesters: May induce premature uterine contractions or fetal bradycardia. Use only if clearly needed and potential benefit justifies risk. |
■ FDA Black Box Warning
May cause bradycardia, asystole, and severe cholinergic reactions; atropine must be immediately available.
| Serious Effects |
Hypersensitivity to edrophonium or any component; mechanical intestinal or urinary obstruction; concurrent use with depolarizing neuromuscular blockers (succinylcholine) due to prolonged apnea.
| Precautions | Risk of severe bradycardia, hypotension, and syncope; bronchoconstriction in asthmatics; increased airway secretions; seizures; urinary tract obstruction; drug interaction with neuromuscular blocking agents. |
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| Fetal Monitoring |
| Monitor fetal heart rate and uterine activity during administration, especially if used for myasthenia gravis crisis or to reverse neuromuscular blockade. Assess maternal respiratory function and muscle strength. Observe for signs of cholinergic crisis (e.g., excessive salivation, bradycardia, hypotension). |
| Fertility Effects | No data on human fertility effects. Animal studies have not been conducted. Potential indirect effects from underlying disease (e.g., myasthenia gravis) on fertility. |