pralidoxime


pralidoxime

 [pral″ĭ-doks´ēm] a cholinesterase reactivator whose salts are used in treatment of organophosphorus compound poisoning; it also has limited value in counteracting overdosage of carbamate-type inhibitors" >cholinesterase inhibitors in persons being treated for myasthenia gravis.

pralidoxime

(pra-li-dox-eem) pralidoxime,

Protopam

(trade name)

Classification

Therapeutic: antidotes
Pharmacologic: cholinesterase reactivators
Pregnancy Category: C

Indications

Early (first 24–36 hr) treatment of organophosphate anticholinesterase insecticide poisoning, usually with atropine and supportive measures, including mechanical ventilation, if necessary.Management of anticholinesterase (neostigmine, pyridostigmine, ambenonium, or nerve gas) overdosage.

Action

Reactivates cholinesterase after poisoning with anticholinesterase agents.May also directly inactivate organophosphates.

Therapeutic effects

Reversal of muscle paralysis after organophosphate poisoning.

Pharmacokinetics

Absorption: IV administration results in complete bioavailability.Distribution: Widely distributed throughout extracellular water. Does not appear to enter the CNS.Metabolism and Excretion: 80–90% excreted unchanged by the kidneys.Half-life: 0.8–2.7 hr.

Time/action profile (plasma levels)

ROUTEONSETPEAKDURATION
IMunknown10–20 minunknown
IVunknown5–15 minunknown

Contraindications/Precautions

Contraindicated in: Hypersensitivity.Use Cautiously in: Myasthenia gravis (may precipitate myasthenic crisis); Renal impairment (dose ↓ required); Efficacy in carbamate insecticide poisoning is not known (may ↑ toxicity); Obstetric / Lactation: Safety not established.

Adverse Reactions/Side Effects

Central nervous system

  • dizziness
  • drowsiness
  • headache

Ear, Eye, Nose, Throat

  • blurred vision
  • diplopia
  • impaired accommodation

Respiratory

  • laryngospasm (life-threatening)
  • hyperventilation

Cardiovascular

  • tachycardia

Gastrointestinal

  • nausea

Dermatologic

  • rash

Local

  • pain at injection site

Musculoskeletal

  • muscle rigidity
  • muscle weakness
  • neuromuscular blockade

Interactions

Drug-Drug interaction

Avoid concurrent use with succinylcholine, morphine, aminophylline, theophylline, reserpine, and respiratory depressants, including barbiturates, opioid analgesics, and sedative/hypnotics, in patients with anticholinesterase poisoning.

Route/Dosage

IV route is preferred. In organophosphate poisoning, atropine 2–4 mg IV is given concurrently after hypoxemia is improved.Atropine is repeated q 5–10 min until toxicity is encountered and is then continued for at least 48 hrOrganophosphate PoisoningIntravenous (Adults) 1–2 g; may be repeated in 1 hr if muscle paralysis is still present. Additional doses may be given q 10–12 hr if muscle weakness persists. IV route is preferred; if not available, may be given IM or subcut.Intramuscular (Adults and Children ≤16 yr and ≥40 kg) Mild symptoms—600 mg; if mild symptoms persist after 15 min, given another 600 mg; if mild symptoms persist after 15 min, given another 600 mg; if symptoms continue to persist after 1 hr of last 600–mg dose, may repeat dosing regimen of three 600–mg doses given 15 min apart; Severe symptoms—Administer three 600–mg doses in rapid succession (total of 1800 mg); if symptoms continue to persist after 1 hr of last 600–mg dose, may repeat dosing regimen of three 600–mg doses given in rapid succession.Intravenous (Children ≤16 yr) Give loading dose of 20–50 mg/kg over 15–30 min; after loading dose, may give another dose of 20–50 mg/kg over 15–30 min in 1 hr if muscle paralysis is still present (can repeat dose q 10–12 hr as needed) or initiate continuous infusion of 10–20 mg/kg/hr. IV route is preferred; if not available, may be given IM or subcut.Intramuscular (Children ≤16 yr and <40 kg) Mild symptoms—15 mg/kg; if mild symptoms persist after 15 min, given another 15 mg/kg; if mild symptoms persist after 15 min, given another 15 mg/kg; if symptoms continue to persist after 1 hr of last 15 mg/kg dose, may repeat dosing regimen of three 15 mg/kg doses given 15 min apart; Severe symptoms—Administer three 15 mg/kg doses in rapid succession; if symptoms continue to persist after 1 hr of last 15 mg/kg dose, may repeat dosing regimen of three 15 mg/kg doses given in rapid succession.Anticholinesterase OverdoseIntravenous (Adults) 1–2 g, followed by increments of 250 mg q 5 min as needed.

Availability (generic available)

Powder for injection: 1 g/vial

Nursing implications

Nursing assessment

  • Determine type of insecticide and time of patient’s exposure. Therapy should begin as soon as possible within 24 hr. Contact poison control center for complete information on the specific insecticide.
  • Monitor neuromuscular status before and periodically throughout therapy. Document skeletal muscle strength, tidal volume, and vital capacity. Note presence of nicotinic effects of anticholinesterases (twitching, muscle cramps, fasciculations, weakness, pallor, tachycardia, increased BP).
  • Closely monitor respirations, pulse, and BP. Rapid IV infusion rate may cause tachycardia, laryngospasm, muscle rigidity, and hypertension. If hypertension occurs, infusion rate may be decreased or infusion discontinued. Phentolamine may be required to control BP.
  • Lab Test Considerations: May cause ↑ AST, ALT, and CPK levels. These usually return to normal in 2 wk.

Potential Nursing Diagnoses

Risk for injury (Indications)
Ineffective airway clearance (Indications)

Implementation

  • Concurrent atropine and supportive measures (suctioning, intubation, and ventilation) may be ordered. Atropine 2–6 mg IV in adults (50–100 mcg/kg in children) is given concurrently. If patient is cyanotic, give atropine IM while improving ventilatory status. Atropine is repeated every 5–60 min until toxicity is encountered and is then continued for at least 48 hr. Atropine is used to reverse muscarinic effects (bronchoconstriction, dyspnea, cough, increased bronchial secretions, nausea, vomiting, abdominal cramps, diarrhea, increased sweating, salivation, lacrimation, bradycardia, decreased BP, miosis, blurred vision, urinary frequency, incontinence) of anticholinesterases. Pralidoxime is effective only against nicotinic effects.
    • Dose may need to be repeated every 3–8 hr if insecticide was ingested; absorption from bowel may continue.
    • Emergency kit containing pralidoxime, sterile water for injection, 20-mL syringe, needle, and alcohol swab is commercially available for subcut, IM, or IV injection.
    • If dermal exposure has occurred, remove clothing and thoroughly wash hair and skin first in sodium bicarbonate, then with alcohol as soon as possible. Health care workers should wear gloves to prevent self-exposure. Carefully dispose of clothing to prevent contamination of others.
  • Intramuscular: Subcutaneous: May be administered IM or subcut in patients unable to tolerate IV infusion. Reconstitute by adding 3.3 mL of Sterile Water for Injection to the 1000 mg vial for a concentration of 300 mg/mL. Do not administer solutions that are discolored or contain particulate matter.
  • Intravenous Administration
  • Diluent: Reconstitute vial containing 1 g of powdered pralidoxime with 20 mL of sterile water for injection. May be administered without further dilution to patients who cannot tolerate IV infusion (for example, pulmonary edema). Concentration: Concentration will be 50 mg/mL..
  • Rate: Administer over at least 5 min; not to exceed 200 mg/min.
  • Intermittent Infusion: Diluent: Dilute reconstituted pralidoxime in 100 mL of 0.9% NaCl.
  • Rate: Infuse over 15–30 min.

Patient/Family Teaching

  • Explain purpose of medication to patient.

Evaluation/Desired Outcomes

  • Reversal of respiratory and skeletal muscle weakness caused by exposure to organophosphate anticholinesterase insecticides or anticholesterase overdose.