Dantrolene

Absorption

Bioavailability is 70%.

Toxicity

Oral LD50 in rats is 7400 mg/kg. Symptoms which may occur in case of overdose include, but are not limited to, muscular weakness and alterations in the state of consciousness (e.g., lethargy, coma), vomiting, diarrhea, and crystalluria.

Originator

Dantrium,Norwich Eaton ,US,1974

The Uses of Dantrolene

Dantrolene acts as a skeletal muscle relaxant through inhibition of Ca2+ release through ryanodine receptor channels.

The Uses of Dantrolene

Relaxant (skeletal muscle).

Indications

For use, along with appropriate supportive measures, for the management of the fulminant hypermetabolism of skeletal muscle characteristic of malignant hyperthermia crises in patients of all ages. Also used preoperatively, and sometimes postoperatively, to prevent or attenuate the development of clinical and laboratory signs of malignant hyperthermia in individuals judged to be malignant hyperthermia susceptible.

Background

Chemically, dantrolene is a hydantoin derivative, but does not exhibit antiepileptic activity like other hydantoin derivates such as phenytoin.

Definition

ChEBI: The hydrazone resulting from the formal condensation of 5-(4-nitrophenyl)furfural with 1-aminohydantoin.

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.

brand name

Dantrium (Procter & Gamble).

Therapeutic Function

Muscle relaxant

General Description

Crystals (in aqueous DMF).

Air & Water Reactions

Slightly water soluble. Dantrolene may be sensitive to heat and air .

Reactivity Profile

A nitrated amine derivative. Amines are chemical bases. They neutralize acids to form salts plus water. These acid-base reactions are exothermic. The amount of heat that is evolved per mole of amine in a neutralization is largely independent of the strength of the amine as a base. Amines may be incompatible with isocyanates, halogenated organics, peroxides, phenols (acidic), epoxides, anhydrides, and acid halides. Flammable gaseous hydrogen is generated by amines in combination with strong reducing agents, such as hydrides.

Health Hazard

SYMPTOMS: When ingested, symptoms of exposure may include drowsiness, dizziness, weakness, general malaise, fatigue, diarrhea, constipation, gastrointestinal bleeding, anorexia, abdominal cramps, hepatitis, speech disturbance, seizure, headache, light-headedness, insomnia, tachycardia, phlebitis, mental depression, mental confusion, nervousness, abdominal hair growth, rash, sweating, backache, chills and fever.

Fire Hazard

Flash point data for Dantrolene are not available. Dantrolene is probably combustible.

Pharmacokinetics

Dantrolene is classified as a direct-acting skeletal muscle relaxant. It is currently the only specific and effective treatment for malignant hyperthermia. In isolated nerve-muscle preparation, Dantrium has been shown to produce relaxation by affecting the contractile response of the muscle at a site beyond the myoneural junction. In skeletal muscle, Dantrium dissociates excitation-contraction coupling, probably by interfering with the release of Ca2+ from the sarcoplasmic reticulum. In the anesthetic-induced malignant hyperthermia syndrome, evidence points to an intrinsic abnormality of skeletal muscle tissue. In selected humans, it has been postulated that “triggering agents” (e.g.,general anesthetics and depolarizing neuromuscular blocking agents) produce a change within the cell which results in an elevated myoplasmic calcium. This elevated myoplasmic calcium activates acute cellular catabolic processes that cascade to the malignant hyperthermia crisis. It is hypothesized that addition of Dantrium to the “triggered” malignant hyperthermic muscle cell reestablishes a normal level of ionized calcium in the myoplasm.

Metabolism

Hepatic, most likely by hepatic microsomal enzymes. Its major metabolites in body fluids are 5-hydroxydantrolene and an acetylamino metabolite of dantrolene. Another metabolite with an unknown structure appears related to the latter. Dantrium may also undergo hydrolysis and subsequent oxidation forming nitrophenylfuroic acid.