Methohexital Sodium - Methohexital Sodium injection (Methohexital Sodium)

Methohexital Sodium for Injection can be used in adults as follows:

• For
  intravenous
  induction of anesthesia prior to the use of other general anesthetic agents.
• For
  intravenous
  induction of anesthesia and as an adjunct to subpotent inhalational anesthetic agents (such as nitrous oxide in oxygen) for short surgical procedures; Methohexital Sodium for Injection may be given by infusion or intermittent injection.
• For use along with other parenteral agents, usually narcotic analgesics, to supplement subpotent inhalational anesthetic agents (such as nitrous oxide in oxygen) for longer surgical procedures.
• As
  intravenous
  anesthesia for short surgical, diagnostic, or therapeutic procedures associated with minimal painful stimuli (See
  WARNINGS
  ).
• As an agent for inducing a hypnotic state.

Methohexital Sodium for Injection can be used in

• For rectal or
  intramuscular 
  induction
  of anesthesia prior to the use of other general anesthetic agents.
• For rectal or
  intramuscular 
  induction
  of anesthesia and as an adjunct to subpotent inhalational anesthetic agents for short surgical procedures.
• As rectal or
  intramuscular 
  anesthesia for short surgical, diagnostic, or therapeutic procedures associated with minimal painful stimuli.

Facilities for assisting ventilation and administering oxygen are necessary adjuncts for all routes of administration of anesthesia. Since cardiorespiratory arrest may occur, patients should be observed carefully during and after use of Methohexital sodium for injection. Age- and size- appropriate resuscitative equipment (i.e., intubation and cardioversion equipment, oxygen, suction, and a secure intravenous line) and personnel qualified in its use must be immediately available.

Preanesthetic medication is generally advisable. Methohexital Sodium for Injection may be used with any of the recognized preanesthetic medications.

FOLLOW DILUTION INSTRUCTIONS EXACTLY.

Freshly prepare solutions of Methohexital Sodium for Injection and use promptly. Reconstituted solutions of Methohexital Sodium for Injection are chemically stable at room temperature for 24 hours.

ONLY USE BACTERIOSTATIC-FREE DILUENT - Recommended diluents are based on route of administration (See 

Incompatible diluents: Lactated Ringer's Injection

1% solutions (10 mg/mL) should be prepared for intermittent intravenous and rectal administration; 0.2% solutions (2 mg/mL) should be prepared for continuous intravenous drug administration; 5% solutions (50 mg/mL) should be prepared for intramuscular administration.

Contents of vials should be diluted as follows:

The preferred diluent for intermittent intravenous and rectal administration is Sterile Water for Injection. 5% Dextrose Injection, or 0.9% Sodium Chloride Injection are also acceptable diluents.

For continuous drip anesthesia, prepare a 0.2% solution by adding 500 mg of Methohexital Sodium for Injection to 250 mL of diluent. For this dilution, either 5% glucose solution or isotonic (0.9%) sodium chloride solution ONLY is recommended as the diluent instead of sterile water for injection in order to avoid extreme hypotonicity.

The preferred diluent for intramuscular administration is Sterile Water for Injection. 0.9% Sodium Chloride Injection is also an acceptable diluent.

Dosage is highly individualized; the drug should be administered only by those completely familiar with its quantitative differences from other barbiturate anesthetics.

Methohexital Sodium for Injection is administered intravenously in a concentration of no higher than 1 %. Higher concentrations markedly increase the incidence of muscular movements and irregularities in respiration and blood pressure.

For induction of anesthesia, a 1% solution is administered at a rate of about 1 mL/5 seconds. Gaseous anesthetics and/or skeletal muscle relaxants may be administered concomitantly. The dose required for induction may range from 50 to 120 mg or more but averages about 70 mg. The usual dosage in adults ranges from 1 to 1.5 mg/kg. The induction dose usually provides anesthesia for 5 to 7 minutes

Maintenance of anesthesia may be accomplished by intermittent injections of the 1% solution or, more easily, by continuous intravenous drip of a 0.2% solution. Intermittent injections of about 20 to 40 mg (2 to 4 mL of a 1% solution) may be given as required, usually every 4 to 7 minutes. For continuous drip, the average rate of administration is about 3 mL of a 0.2% solution/minute (1 drop/second). The rate of flow must be individualized for each patient. For longer surgical procedures, gradual reduction in the rate of administration is recommended (See discussion of prolonged administration in 

Methohexital Sodium for Injection is Administered intramuscularly in a 5% concentration and administered rectally as a 1% solution.

For the induction of anesthesia by the intramuscular route of administration, the usual dose ranges from 6.6 to 10 mg/kg of the 5% concentration. For rectal administration, the usual dose for induction is 25 mg/kg using the 1% solution.

Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.

Solutions of Methohexital Sodium for Injection should not be mixed in the same syringe or administered simultaneously during intravenous infusion through the same needle with acid solutions, such as atropine sulfate, metocurine iodide, and succinylcholine chloride. Alteration of pH may cause free barbituric acid to be precipitated. Solubility of the soluble sodium salts of barbiturates, including Methohexital Sodium, is maintained only at a relatively high (basic) pH.

Because of numerous requests from anesthesiologists for information regarding the chemical compatibility of these mixtures, the following chart contains information obtained from compatibility studies in which a 1 % solution of Methohexital Sodium for Injection was mixed with therapeutic amounts of agents whose solutions have a low (acid) pH.

Side effects associated with Methohexital Sodium for Injection are extensions of pharmacologic effects and include:

Circulatory depression, thrombophlebitis, hypotension, tachycardia, peripheral vascular collapse, and convulsions in association with cardiorespiratory arrest

Respiratory depression (including apnea), cardiorespiratory arrest, laryngospasm, bronchospasm, hiccups, and dyspnea

Skeletal muscle hyperactivity (twitching), injury to nerves adjacent to injection site, and seizures

Emergence delirium, restlessness, and anxiety may occur, especially in the presence of postoperative pain

Nausea, emesis, abdominal pain, and liver function tests abnormal

Erythema, pruritus, urticaria, and cases of anaphylaxis have been reported rarely

Other adverse reactions include pain at injection site, salivation, headache, and rhinitis

Methohexital Sodium for injection, is 2,4,6 (1H, 3H, 5H)-Pyrimidinetrione, 1- methyl-5-(1-methyl-2-pentynyl)-5-(2-propenyl)-, (±)-, monosodium salt and has the empirical formula C₁₄H₁₇N₂NaO₃. Its molecular weight is 284.29.

The structural formula is as follows:

Methohexital sodium is a rapid, ultrashort-acting barbiturate anesthetic. Methohexital sodium for injection is a freeze-dried, sterile, nonpyrogenic mixture of methohexital sodium with 6% anhydrous sodium carbonate added as a buffer. It contains not less than 90% and not more than 110% of the labeled amount of methohexital sodium. It occurs as a white, freeze-dried plug that is freely soluble in water.

This product is oxygen sensitive. The pH of the 1% solution is between 10 and 11; the pH of the 0.2% solution in 5% dextrose is between 9.5 and 10.5.

Methohexital sodium may be administered by direct intravenous injection or continuous intravenous drip, intramuscular or rectal routes (See