DESCRIPTION

Levorphanol (Levo-Dromoran) is a synthetic opiate analgesic, the levo-isomer of dextromethorphan.

FORMS AND USES

Levorphanol is available as a tablet and for subcutaneous injection.

TOXIC DOSE

Respiratory depression can occur at therapeutic doses (2 mg).

PATHOPHYSIOLOGY

• Levorphanol is an opiate receptor agonist with a duration of action similar to that of morphine.
• It may accumulate during repeated administration, leading to toxicity.

EPIDEMIOLOGY

Poisoning is uncommon.

CAUSES

Child neglect or abuse should be considered if the patient is less than 1 year of age, suicide attempt if the patient is over 6 years of age.

PREGNANCY AND LACTATION

• U.S. FDA Category B. Animal studies do indicate a fetal risk and there are no controlled human studies, or animal studies to show an adverse fetal effect, but well-controlled studies in pregnant women do not.
• FDA classification becomes D if used at term.
• Neonatal withdrawal may occur 12-72 hours after delivery.

Section Outline:

• DESCRIPTION
• FORMS AND USES
• TOXIC DOSE
• PATHOPHYSIOLOGY
• EPIDEMIOLOGY
• CAUSES
• PREGNANCY AND LACTATION

DIFFERENTIAL DIAGNOSIS

• Other toxic causes of CNS depression include: Alcohol, other narcotics, clonidine, benzodiazepines, barbiturates, tricyclic antidepressants
• Nontoxic causes of CNS depression: Hypoxia, severe electrolyte abnormalities, hypoglycemia, intracranial bleed, meningitis, encephalitis, postictal state.

SIGNS AND SYMPTOMS

Vital Signs

Bradycardia, hypotension, and bradypnea may occur.

HEENT

Miosis usually occurs with overdose.

Dermatologic

Skin may be cool.

Cardiovascular

Bradycardia, hypotension, and vasodilation may occur.

Pulmonary

• Dose-related respiratory depression is common and may be prolonged in overdose.
• Pulmonary edema can occur with overdose.

Gastrointestinal

• Nausea and vomiting can occur but reportedly less than with morphine.
• Constipation may occur in therapeutic doses.

Neurologic

• Somnolence progressing to coma occurs with overdose.
• There may be less CNS depression than with a morphine overdose.

PROCEDURES AND LABORATORY TESTS

Essential Tests

No tests may be needed in asymptomatic patients.

Recommended Tests

• All patients with altered mental status should have blood glucose level determined.
• Serum electrolytes, BUN, creatinine to assess cause of altered mental status.
• Pulse oximetry or arterial blood gases should be obtained to evaluate oxygenation.
• Head CT, lumbar puncture, urine toxicology, and other studies should be performed as needed to evaluate other causes of altered mental status.

Section Outline:

• DIFFERENTIAL DIAGNOSIS
• SIGNS AND SYMPTOMS
  • Vital Signs
  • HEENT
  • Dermatologic
  • Cardiovascular
  • Pulmonary
  • Gastrointestinal
  • Neurologic
• PROCEDURES AND LABORATORY TESTS
  • Essential Tests
  • Recommended Tests

• Treatment should focus on control of airway and administration of naloxone.
• Dose and time of exposure need to be determined for all substances involved.

DIRECTING PATIENT COURSE

The health-care professional should call the poison control center when:

• Severe or persistent effects develop.
• Coingestant, drug interaction, or underlying disease presents an unusual problem.

The patient should be referred to a health-care facility when:

• Suicide or homicide attempt is possible.
• Toxic effects develop.
• Coingestant, drug interaction, or underlying disease presents an unusual problem.

Admission Considerations

Patients should be admitted if they have persistently altered mental status or require a second dose of opiate antagonist during their 6-hour observation period.

DECONTAMINATION

Out of Hospital

Emesis should not be induced.

In Hospital

• Gastric lavage (after appropriate airway management) should be performed in pediatric (tube size 24-32 French) or adult (tube size 36-42 French) patients presenting within 1 hour of a large ingestion or if serious effects are present.
• One dose of activated charcoal (1-2 g/kg) should be administered without a cathartic if a substantial ingestion has occurred within the previous few hours.

ANTIDOTES

Naloxone is a specific antidote for levorphanol poisoning.

• An adult or child should be administered 2 mg intravenously for respiratory depression.
• The dose may be repeated up to 10 mg, but most patients will respond to 2 mg.
• Naloxone may precipitate withdrawal in dependent patients.

ADJUNCTIVE TREATMENT

Patients should be placed on a cardiac monitor, receive oxygen, and have intravenous access established.

Section Outline:

• DIRECTING PATIENT COURSE
  • Admission Considerations
• DECONTAMINATION
  • Out of Hospital
  • In Hospital
• ANTIDOTES
• ADJUNCTIVE TREATMENT

PATIENT MONITORING

Cardiac and respiratory function should be monitored continuously.

EXPECTED COURSE AND PROGNOSIS

Complete recovery is expected unless sequelae of hypoxia develop before medical treatment can be provided.

DISCHARGE CRITERIA/INSTRUCTIONS

An asymptomatic patient may be discharged from the emergency deparment or hospital after adequate decontamination and 4 hours of observation after the administration of naloxone.

Section Outline:

• PATIENT MONITORING
• EXPECTED COURSE AND PROGNOSIS
• DISCHARGE CRITERIA/INSTRUCTIONS

Naloxone effect may dissipate over 30-60 minutes, allowing CNS and respiratory depression to recur.

Poisoning by analgesics, antipyretics, and antirheumatics.

970.1

Poisoning by central nervous system stimulants: opiate antagonists.

See Also: SECTION III, Naloxone and Nalmephene chapter.

RECOMMENDED READING

Ellenhorn MJ. The opiates. Medical toxicology. Baltimore: Williams & Wilkins, 1997:405-412.

Author: Kennon Heard

Reviewer: Richard C. Dart