ARFONAD
Clinical safety rating
cautionComprehensive clinical and safety monograph for ARFONAD (ARFONAD).
Arfonad (trimethaphan camsylate) is a ganglionic blocking agent that competitively inhibits nicotinic acetylcholine receptors at autonomic ganglia, resulting in sympathetic and parasympathetic blockade. This leads to vasodilation and decreased peripheral vascular resistance.
| Metabolism | Primarily metabolized by plasma pseudocholinesterase (butyrylcholinesterase); also undergoes hepatic metabolism. |
| Excretion | Primarily renal excretion of unchanged drug (approximately 30-50%) with the remainder metabolized; minimal biliary/fecal elimination. |
| Half-life | Terminal elimination half-life is approximately 1-2 minutes due to rapid hydrolysis by plasma esterases, leading to ultrashort duration. |
| Protein binding | Approximately 50% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Approximately 0.3 L/kg, indicating distribution mainly in extracellular fluid. |
| Bioavailability | Only administered intravenously; oral bioavailability is negligible due to rapid hydrolysis. |
| Onset of Action | Intravenous: within 1-2 minutes. |
| Duration of Action | Intravenous: 5-10 minutes after infusion cessation; titrated by continuous infusion for blood pressure control. |
| Molecular Weight | 387.43 |
Intravenous infusion: 0.5-1 mg/min initially, titrated to desired blood pressure reduction; typical maintenance 1-4 mg/min.
| Dosage form | INJECTABLE |
| Renal impairment | No specific dose adjustment recommended based on GFR; use with caution in severe renal impairment due to potential for accumulation. |
| Liver impairment | No specific Child-Pugh based dose adjustments; caution in severe hepatic impairment. |
| Pediatric use | Not recommended in pediatric patients due to lack of safety and efficacy data. |
| Geriatric use | Initiate at lower end of dosing range (0.5 mg/min) and titrate slowly due to increased sensitivity to hypotension and reduced metabolic clearance. |
| 1st trimester | Contraindicated: Teratogenic effects observed in animal studies; risk of fetal bradycardia and hypotension. |
| 2nd trimester | Contraindicated: Risk of fetal hypotension and reduced placental perfusion. |
| 3rd trimester | Contraindicated: May cause fetal bradycardia, hypotension, and neonatal respiratory depression. |
Clinical note
Comprehensive clinical and safety monograph for ARFONAD (ARFONAD).
| Placental transfer | Crosses placenta rapidly; fetal levels may approach maternal levels. |
| Breastfeeding | Excreted in breast milk in low amounts; potential for infant bradycardia and hypotension. Use only if clearly needed and monitor infant for adverse effects. |
| Lactation Rating | L4 (Possibly Hazardous) |
| Teratogenic Risk | Arfonad (trimethaphan camsylate) is a ganglionic blocker used for controlled hypotension. FDA Pregnancy Category C. Animal studies are inadequate. No well-controlled human studies. Potential for fetal harm due to maternal hypotension and reduced uteroplacental perfusion. First trimester: theoretical risk of teratogenicity due to altered hemodynamics, but no specific malformations reported. Second and third trimesters: risk of fetal hypoxia, bradycardia, and acidosis due to maternal hypotension. Avoid use in pregnancy unless clearly needed. |
| Fetal Monitoring | Continuous maternal blood pressure monitoring and fetal heart rate monitoring during infusion. Assess maternal oxygen saturation and signs of uterine hypoperfusion (decreased urine output). Monitor fetal heart rate patterns for evidence of distress. After delivery, monitor neonate for hypotension and respiratory depression. |
| Fertility Effects | No evidence of direct effects on fertility in humans. Animal studies not available. Theoretical impairment due to autonomic blockade affecting reproductive function, but clinically not significant. |
■ FDA Black Box Warning
None.
| Serious Effects |
Hypersensitivity to trimethaphan or any componentPre-existing severe hypotensionInadequate cerebral circulationInadequate coronary circulationMyasthenia gravisUncorrected anemiaUncorrected hypovolemiaSevere respiratory depressionSevere hepatic impairment
| Precautions | May cause profound hypotension; monitor blood pressure closely., Use with caution in patients with hypovolemia, myocardial ischemia, or cerebrovascular insufficiency., Can cause histamine release leading to bronchospasm; avoid in patients with asthma., May cause pupillary dilation and cycloplegia; use caution with glaucoma., Can inhibit plasma pseudocholinesterase; prolonged effect in patients with atypical pseudocholinesterase. |
| Food/Dietary | No specific food interactions; however, avoid large meals before surgery as general fasting guidelines apply. |
| Clinical Pearls | Arfonad (trimethaphan camsylate) is a ganglionic blocker used for controlled hypotension during surgery. Monitor blood pressure closely as it can cause profound hypotension. Tachyphylaxis develops rapidly. Use with caution in patients with renal impairment, as drug accumulation may occur. Administer via continuous IV infusion, titrating to desired effect. Have vasopressors (e.g., phenylephrine) ready to reverse hypotension. Arfonad can release histamine, so monitor for bronchospasm in asthmatics. |
| Patient Advice | You will receive this medication only in the hospital, typically during surgery. · Your blood pressure will be closely monitored throughout the infusion. · Report any difficulty breathing, hives, or palpitations immediately. · This medication may cause blurred vision, dizziness, or dry mouth; avoid sudden position changes. · Do not stop the infusion abruptly; it will be tapered by your healthcare team. |
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