24868-20-0

Manufacturing Process

5-(p-Nitrophenyl)-2-furaldehyde (40.0 grams, 0.2 mol) is dissolved in dimethylformamide. An aqueous solution of 1-aminohydantoin hydrochloride (30.0 grams, 0.2 mol) is added. The solution is chilled and diluted with water. The crude material is collected and recrystallized from aqueous dimethylformamide to yield 10.0 grams (16%). MP 279°-280°C. This compound is then converted to the sodium salt.

Therapeutic Function

Muscle relaxant

Biological Functions

Dantrolene sodium (Dantrium) is used in the treatment of spasticity due to stroke, spinal injury, multiple sclerosis, or cerebral palsy. It is also the drug of choice in prophylaxis or treatment of malignant hyperthermia. Susceptibility to malignant hyperthermia is due to a rare genetic defect that allows Ca++ release from the sarcoplasmic reticulum to open more easily and close less readily than normal. This leads to a high level of Ca++ in the sarcoplasm, which produces muscle rigidity, oxygen consumption, and heat. Dantrolene acts by blocking Ca++ release from the sarcoplasmic reticulum and uncoupling excitation from contraction. Dantrolene is active orally, although its absorption is slow and incomplete. Its biological half-life (t1/2) is 8.7 hours in adults. The drug is metabolized by liver microsomal enzymes and is eliminated in the urine and bile. It is given IV when treating an attack of malignant hyperthermia. The most prominent and often limiting feature of dantrolene administration is dose-dependent muscle weakness. Other side effects are drowsiness, dizziness, malaise, fatigue, and diarrhea. Symptomatic hepatitis is reported in 0.5% of patients receiving it and fatal hepatitis in up to 0.2%. Contraindications include respiratory muscle weakness and liver disease. It is suggested that patients on dantrolene therapy be given regular liver function tests.

Veterinary Drugs and Treatments

In humans, oral dantrolene is indicated primarily for the treatment associated with upper motor neuron disorders (e.g., multiple sclerosis, cerebral palsy, spinal cord injuries, etc.). In veterinary medicine, its proposed indications include: the prevention and treatment of malignant hyperthermia syndrome in various species, the treatment of functional urethral obstruction due to increased external urethral tone in dogs and cats, the prevention and treatment of equine postanesthetic myositis (PAM), and equine exertional rhabdomyolysis. It has also been recommended for use in the treatment of bites from Black Widow Spiders in small animals and the treatment of porcine stress syndrome.

Drug interactions

Potentially hazardous interactions with other drugsAvoid with other hepatotoxic medication.

Metabolism

Dantrolene is inactivated by hepatic metabolism in the first instance. There are two alternative pathways. Most of the drug is hydroxylated to 5-hydroxydantrolene. The minor pathway involves nitro-reduction to aminodantrolene, which is then acetylated (compound F-490). The 5-hydroxy metabolite is a muscle relaxant with nearly the same potency as the parent molecule, and may have a longer half-life than the parent compound. Compound F-490 is much less potent and is probably inactive at the concentrations achieved in clinical samples. Metabolites are subsequently excreted in the urine in the ratio of 79 5 hydroxy-dantrolene: 17 compound F-490: 4 unaltered dantrolene (salt or free acid). The proportion of drug excreted in the faeces depends upon dose size.

Definition

ChEBI: A hydrate which is the hemiheptahydrate of anhydrous dantrolene sodium.