Pralidoxime Chloride

Description

DESCRIPTION Chemical name: 2-formyl-1-methylpyridinium chloride oxime. Available in the United States as PROTOPAM Chloride for Injection (PROTOPAM Chloride), pralidoxime chloride is frequently referred to as 2-PAM Chloride. Structural formula: C7H9CIN2O M.W. 172.61 Pralidoxime chloride occurs as an odorless, white, nonhygroscopic, crystalline powder which is soluble in water. Stable in air, it melts between 215º and 225º C, with decomposition. The specific activity of the drug resides in the 2-formyl-1-methylpyridinium ion and is independent of the particular salt employed. The chloride is preferred because of physiologic compatibility, excellent water solubility at all temperatures, and high potency per gram, due to its low molecular weight. Pralidoxime chloride is a cholinesterase reactivator. PROTOPAM Chloride for intravenous injection or infusion is prepared by cryo-desiccation. Each vial contains 1000 mg of sterile pralidoxime chloride, and sodium hydroxide to adjust pH, to be reconstituted with 20 mL of Sterile Water for Injection, USP. The pH of the reconstituted solution is 3.5 to 4.5. Intramuscular or subcutaneous injection may be used when intravenous injection is not feasible. PROTOPAM structural formula

What Is Pralidoxime Chloride Used For?

INDICATIONS AND USAGE PROTOPAM Chloride is indicated as an antidote: 1. In the treatment of poisoning due to those pesticides and chemicals (e.g., nerve agents) of the organophosphate class which have anticholinesterase activity and 2. In the control of overdosage by anticholinesterase drugs used in the treatment of myasthenia gravis. The principal indications for the use of PROTOPAM Chloride are muscle weakness and respiratory depression. In severe poisoning, respiratory depression may be due to muscle weakness.

Dosage and Administration

DOSAGE AND ADMINISTRATION Organophosphate Poisoning Treatment should include general supportive care, atropinization, and decontamination, in addition to the use of PROTOPAM Chloride. Treatment is most effective if initiated immediately after poisoning. Administration of PROTOPAM Chloride should be carried out slowly and, preferably, by infusion. If intravenous administration is not feasible, intramuscular or subcutaneous injection should be used. Generally, little is accomplished if PROTOPAM Chloride is given more than 36 hours after termination of exposure to the poison. When the poison has been ingested, it is particularly important to take into account the likelihood of continuing absorption from the lower bowel since this constitutes new exposure and fatal relapses have been reported after initial improvement. In such cases, additional doses of PROTOPAM Chloride may be needed every three to eight hours. In effect, the patient should be “titrated” with PROTOPAM Chloride as long as signs of poisoning recur. As in all cases of organophosphate poisoning, care should be taken to keep the patient under observation for at least 48 to 72 hours. If dermal exposure has occurred, clothing should be removed and the hair and skin washed thoroughly with sodium bicarbonate or alcohol as soon as possible. Supportive care, including airway management, respiratory and cardiovascular support, correction of metabolic abnormalities, and seizure control, may be necessary in cases of severe organophosphate poisoning. Atropine should be given as soon as possible after hypoxemia is improved. Atropine should not be given in the presence of significant hypoxia due to the risk of atropine-induced ventricular fibrillation. In adults, atropine may be given intravenously in doses of 2 to 4 mg. This should be repeated at 5- to 10-minute intervals until full atropinization (secretions are inhibited) or signs of atropine toxicity appear (delirium, hyperthermia, muscle twitching). Some degree of atropinization should be maintained for at least 48 hours, and until any depressed blood cholinesterase activity is reversed. Use of morphine, theophylline, aminophylline, reserpine, and phenothiazine-type tranquilizers should be avoided in patients with organophosphate poisoning (see PRECAUTIONS, Drug Interactions ). Prolonged paralysis has been reported in patients when succinylcholine is given with drugs having anticholinesterase activity; therefore, it should be used with caution. After the effects of atropine become apparent, PROTOPAM Chloride may be administered. Symptoms Of Nerve Agent And Insecticide Poisoning PROTOPAM Chloride dosing is based, in part, on the severity of symptoms of nerve agent intoxication. These symptoms include the following: MILD symptoms:

Side Effects (Adverse Reactions)

ADVERSE REACTIONS Forty to 60 minutes after intramuscular injection, mild to moderate pain may be experienced at the site of injection. Pralidoxime chloride may cause blurred vision, diplopia and impaired accommodation, dizziness, headache, drowsiness, nausea, tachycardia, increased systolic and diastolic blood pressure, hyperventilation, and muscular weakness when given parenterally to normal volunteers who have not been exposed to anticholinesterase poisons. In patients, it is very difficult to differentiate the toxic effects produced by atropine or the organophosphate compounds from those of the drug. Elevations in SGOT and/or SGPT enzyme levels were observed in 1 of 6 normal volunteers given 1200 mg of pralidoxime chloride intramuscularly, and in 4 of 6 volunteers given 1800 mg intramuscularly. Levels returned to normal in about 2 weeks. Transient elevations in creatine phosphokinase were observed in all normal volunteers given the drug. When atropine and pralidoxime chloride are used together, the signs of atropinization may occur earlier than might be expected when atropine is used alone. This is especially true if the total dose of atropine has been large and the administration of pralidoxime chloride has been delayed. Excitement and manic behavior immediately following recovery of consciousness have been reported in several cases. However, similar behavior has occurred in cases of organophosphate poisoning that were not treated with pralidoxime chloride.

Drug Interactions

Drug Interactions When atropine and pralidoxime chloride are used together, the signs of atropinization (flushing, mydriasis, tachycardia, dryness of the mouth and nose) may occur earlier than might be expected when atropine is used alone. This is especially true if the total dose of atropine has been large and the administration of pralidoxime chloride has been delayed. The following precautions should be kept in mind in the treatment of anticholinesterase poisoning, although they do not bear directly on the use of pralidoxime chloride: since barbiturates are potentiated by the anticholinesterases, they should be used cautiously in the treatment of convulsions; morphine, theophylline, aminophylline, reserpine, and phenothiazine-type tranquilizers should be avoided in patients with organophosphate poisoning. Prolonged paralysis has been reported in patients when succinylcholine is given with drugs having anticholinesterase activity; therefore, it should be used with caution.

Contraindications

CONTRAINDICATIONS There are no known absolute contraindications for the use of PROTOPAM Chloride (see PRECAUTIONS, Drug Interactions and DOSAGE AND ADMINISTRATION ). Relative contraindications include known hypersensitivity to the drug and other situations in which the risk of its use clearly outweighs possible benefit.

Pregnancy and Breastfeeding

Pregnancy Teratogenic Effects: Animal reproduction studies have not been conducted with pralidoxime chloride. It is also not known whether pralidoxime chloride can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Pralidoxime chloride should be given to a pregnant woman only if clearly needed.

Nursing Mothers It is not known whether this drug is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when pralidoxime chloride is administered to a nursing woman.

Overdosage

OVERDOSAGE Manifestations of Overdosage Observed in normal subjects only: dizziness, blurred vision, diplopia, headache, impaired accommodation, nausea, slight tachycardia. In therapy, it has been difficult to differentiate side effects due to the drug from those due to the effects of the poison.

How Supplied

HOW SUPPLIED NDC 60977-141-01—Hospital Package: This contains six 20 mL vials of 1 g each of sterile PROTOPAM Chloride (pralidoxime chloride) for Injection white to off-white porous cake*, without diluent or syringe. *When necessary, sodium hydroxide is added during processing to adjust the pH. Storage Store at 20°-25°C (68°-77°F), excursions permitted to 15°-30°C (59°-86°F) [see USP Controlled Room Temperature].