Mexifen

Uses

Mexifen Hydrochloride is a synthetic opioid analgesic, which binds with mu, kappa and delta receptor. Its analgesic potency is equivalent to Morphine on a milligram basis and 10 times more than that of Pentazocine but has lower side effects and less abuse potential than Morphine. The onset of action of Mexifen occurs within 2 to 3 minutes after intravenous administration and in less than 15 minutes following intramuscular injection. The plasma half-life of Mexifen is 5 hours and the duration of analgesic activity is 3 to 6 hours.

Mexifen Hydrochloride is used for the relief of moderate to severe pain. It is used for relief of moderate to severe pain associated with myocardial infarction (MI). Mexifen Hydrochloride can also be used as a supplement to balanced anesthesia, for preoperative and postoperative analgesia, and for obstetrical analgesia during labor and delivery.

Mexifen is also used to associated treatment for these conditions: Severe Pain, Moderate Pain, Obstetrical analgesia during labor and delivery therapy, Perioperative analgesia, Obstetric analgesia

How Mexifen works

The exact mechanism of action is unknown, but is believed to interact with an opiate receptor site in the CNS (probably in or associated with the limbic system). The opiate antagonistic effect may result from competitive inhibition at the opiate receptor, but may also be a result of other mechanisms. Mexifen is thought primarily to be a kappa agonist. It is also a partial mu antagonist analgesic, with some binding to the delta receptor and minimal agonist activity at the sigma receptor.

Dosage

Mexifen dosage

The usual recommended adult dose is 10 mg for a 70 kg individual, administered subcutaneously, intramuscularly or intravenously; this dose may be repeated every 3 to 6 hours as necessary. Dosage should be adjusted according to the severity of the pain, physical status of the patient, and other medications which the patient may bereceiving.

Moderate to severe pain: by intravenous or intramuscular injection 10-20 mg for 70 kg patient, adjusted as required; child up to 0.3 mg/kg repeated once or twice as necessary.

Preoperative anesthesia: by intravenous or intramuscular injection 0.1-0.2 mg/kg.

Obstetrical analgesia during labor & delivery: by intravenous injection 0.3-1 mg/kg over 10-15 minutes with maintenance doses of 0.25-0.5 mg/kg in single intravenous administration as required.

Intraoperative analgesia: by intravenous injection 0.25-0.5 mg/kg at 30 minutes intervals.

Myocardial infarction: By slow intravenous injection 10-20 mg, repeated after 30 minutes if necessary. Larger dose is required when used as supplement of anesthesia than that required for analgesia.

Children from 18 months to 15 years old: usually 0.2 mg/ kg body-weight, given preferably by intravenous or intramuscular injection. Maintenance doses may be given at intervals of 4 to 6 hours or the dose must be determined by the physician.

Side Effects

Generally Mexifen is well tolerated. However few side-effects like sedation, sweating, nausea, vomiting, dizziness, vertigo, dry mouth, headache, respiratory depression, dyspnea and asthma may be seen.

Toxicity

Oral, acute LD50 is 1100 mg/kg in dog. Symptoms of overdose include primarily sleepiness and mild dysphoria.

Precaution

Caution should be taken in the following conditions: impaired respiration, impaired renal or hepatic function, billiary tract surgery, myocardial infarction and hypotension.

Interaction

No hazardous interactions have been identified with Mexifen; however, interactions described with other opioids may be anticipated. Patient receiving a narcotic analgesic, general anesthesia, phenothiazines or other tranquilizers, sedatives, hypnotics, or other CNS depressants (including alcohol) concomitantly with Mexifen may exhibit an additive effect.

Food Interaction

• Avoid alcohol. Ingesting alcohol may increase the sedative and CNS depressant effects of nalbuphine.

Mexifen Alcohol interaction

[Moderate] GENERALLY AVOID:

Ethanol may potentiate the central nervous system (CNS) depressant effects of opioid analgesics.

Concomitant use may result in additive CNS depression and impairment of judgment, thinking, and psychomotor skills.

In more severe cases, hypotension, respiratory depression, profound sedation, coma, or even death may occur.

Concomitant use of opioid analgesics with ethanol should be avoided.

Mexifen Drug Interaction

Major: meperidine, pregabalin, alprazolamModerate: promethazine, valproic acid, midazolam, ondansetronUnknown: aspirin, epinephrine, amoxicillin / clavulanate, sulfamethoxazole / trimethoprim, albuterol / ipratropium, glucose, heparin, methylergonovine, insulin isophane, acetaminophen, cyanocobalamin, cholecalciferol, phytonadione

Mexifen Disease Interaction

Major: impaired GI motility, infectious diarrhea, liver disease, prematurity, gastrointestinal obstruction, acute MI, drug dependence, intracranial pressure, respiratory depressionModerate: adrenal insufficiency, biliary spasm, hypothyroidism, renal dysfunction, seizure disorders, urinary retention

Elimination Route

The mean absolute bioavailability was 81% and 83% for the 10 and 20 mg intramuscular doses, respectively, and 79% and 76% following 10 and 20 mg of subcutaneous nalbuphine. Clinical studies show that the duration of analgesic activity of the drug can range from 3 to 6 hours.

Half Life

The plasma half-life of nalbuphine is about 5 hours.

Pregnancy & Breastfeeding use

Pregnancy category B. The placental transfer of Mexifen is high and rapid. There are no well-controlled studies in pregnant women. This drug should be used during pregnancy only if clearly needed. Limited data suggest that Mexifen is excreted in maternal milk but only in a small amount (less than 1% of the administered dose) and with a clinically insignificant effect. Caution should be exercised when Mexifen is administered to a nursing woman.

Contraindication

Known hypersensitivity to Mexifen Hydrochloride.

Acute Overdose

Sleepiness & mild dyspnea may occur due to overdose. The immediate intravenous administration of an opiate antagonist such as Naloxone or Nalmefene is a specific antidote. Oxygen, intravenous fluids, vasopressors and other supportive measures should be used as indicated

Storage Condition

Keep it in a cool and dry place, protected from light and moisture.

Innovators Monograph

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