FLAXEDIL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for FLAXEDIL (FLAXEDIL).
FLAXEDIL (gallamine triethiodide) is a nondepolarizing neuromuscular blocking agent that competitively antagonizes acetylcholine at nicotinic receptors at the neuromuscular junction, preventing muscle contraction.
| Metabolism | Primarily excreted unchanged by the kidneys via glomerular filtration; minimal hepatic metabolism. |
| Excretion | Flaxedil (gallamine triethiodide) is excreted primarily unchanged by the kidneys via glomerular filtration. Approximately 90-95% of an administered dose is eliminated in urine within 24 hours, with the remainder excreted in feces (<5%) via biliary elimination. |
| Half-life | The terminal elimination half-life of gallamine is approximately 2-4 hours in patients with normal renal function. This half-life is inversely related to creatinine clearance, and may be prolonged to 12-24 hours or more in patients with renal impairment, leading to cumulative effects and prolonged neuromuscular blockade. |
| Protein binding | Gallamine has negligible protein binding (<10%), binding weakly to albumin and other plasma proteins. |
| Volume of Distribution | The volume of distribution (Vd) of gallamine is approximately 0.2-0.3 L/kg, indicating distribution primarily within the extracellular fluid space. This low Vd is consistent with its high polarity and limited tissue penetration. |
| Bioavailability | Gallamine is poorly absorbed after oral administration (bioavailability <5%) due to its quaternary ammonium structure. Intravenous administration provides 100% bioavailability. Intramuscular bioavailability is approximately 80-90%, with variable absorption depending on injection site. |
| Onset of Action | Onset of action after intravenous administration is rapid, typically within 1-2 minutes. Onset is slower after intramuscular injection, occurring within 2-5 minutes. |
| Duration of Action | The duration of neuromuscular blockade after a single intravenous dose of 1 mg/kg is approximately 20-40 minutes for clinical relaxation (return of 25% twitch height), with full recovery (90% twitch) in 60-90 minutes. Effects are prolonged in renal failure and with repeated dosing. |
0.08-0.12 mg/kg IV bolus for neuromuscular blockade; additional doses of 0.01-0.02 mg/kg as needed.
| Dosage form | INJECTABLE |
| Renal impairment | Not recommended in patients with GFR < 30 mL/min; for GFR 30-50 mL/min, use 50% of usual dose and monitor recovery. Not dialyzable. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use. |
| Pediatric use | Neonates and infants: 0.04-0.08 mg/kg IV; children: 0.06-0.1 mg/kg IV; titrate to effect. Not approved for pediatric use in many countries. |
| Geriatric use | Initiate at 0.04-0.06 mg/kg IV; monitor for prolonged recovery and cardiovascular effects due to reduced clearance and volume of distribution. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for FLAXEDIL (FLAXEDIL).
| Breastfeeding | It is unknown whether FLAXEDIL is excreted in human breast milk. The M/P ratio has not been determined. Because of the potential for neuromuscular blockade and adverse reactions in nursing infants, breastfeeding should be discontinued during therapy or the drug avoided in nursing mothers. |
| Teratogenic Risk | FLAXEDIL (gallamine triethiodide) is a non-depolarizing neuromuscular blocking agent. Data on teratogenicity in humans are insufficient. In animal studies, no teratogenic effects were observed at doses up to 1.5 mg/kg in rats and 0.5 mg/kg in rabbits. However, use during pregnancy should be avoided unless clearly necessary. During the first trimester, theoretical risk exists due to lack of data. In the second and third trimesters, use may be considered if benefit outweighs risk, but careful monitoring is required. Near term, potential for neonatal respiratory depression and muscle weakness exists if used during labor and delivery. |
■ FDA Black Box Warning
Must be administered only by experienced clinicians trained in airway management; risk of prolonged paralysis and respiratory depression requiring ventilatory support; have immediate access to reversal agents.
| Serious Effects |
Hypersensitivity to gallamine or any component; myasthenia gravis; known history of malignant hyperthermia; severe renal impairment (CrCl < 30 mL/min).
| Precautions | Risk of histamine release causing bronchospasm; prolonged use may cause tachyphylaxis; use caution in renal impairment (dose adjustment needed); monitor neuromuscular function with nerve stimulator. |
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| Fetal Monitoring | Maternal: Continuous monitoring of vital signs (heart rate, blood pressure, respiratory rate), oxygen saturation via pulse oximetry, end-tidal CO2, and neuromuscular function using train-of-four (TOF) monitoring. Fetal: Continuous fetal heart rate monitoring during prolonged use near term. Neonatal: Assess for signs of neuromuscular blockade (weakness, respiratory depression) after delivery. |
| Fertility Effects | No specific studies on fertility in humans. Animal studies show no effects on fertility at doses up to 1 mg/kg in rats. However, the drug's mechanism of action (neuromuscular blockade) is not expected to directly impact fertility. Indirect effects due to prolonged hospitalization or critical illness may affect reproductive function. |