DRUG ABUSE AND DEPENDENCE

Controlled Substance

Loperamide is not a controlled substance.

Abuse

Loperamide is a mu-opioid agonist. A human abuse potential study of loperamide hydrochloride at single doses up to 60 mg (3.75 times the recommended maximum adult dosage of 16 mg per day) was compared, in a double-blind cross-over design using nine subjects who had been active opiate users, to a threshold dose of codeine sulfate at 120 mg (96 mg base) or placebo. This resulted in one subject (11%) feeling a drug on placebo and identifying it as "dope" (heroin) and liking it slightly. Codeine was felt by 56% of subjects and identified as "dope" by 44%. Loperamide was felt by 44% of subjects and identified as "dope" by 11% and possibly dope mixed with some other kind of drug by another 22%. Loperamide abuse and misuse have been reported, especially at doses of 60 mg or greater. Loperamide can have greater CNS opioid effects at higher doses or with co-administration of drugs that increase systemic exposure and/or increase CNS penetration of loperamide (through inhibition of the CYP450 enzyme system or inhibition of P-glycoprotein). Loperamide is primarily being misused for relief from opioid withdrawal, and abused by a few users who obtain some (reportedly mild- moderate) level of euphoria.

Dependence

In animals, parenteral administration of loperamide hydrochloride can cause physical dependence, cross-tolerance to opioids, and all the other pharmacologic effects typical of mu-opioid agonists.

Studies in morphine-dependent monkeys demonstrated that loperamide hydrochloride at doses above those recommended for humans prevented signs of morphine withdrawal.

OVERDOSAGE

The use of higher than recommended loperamide hydrochloride doses may result in life-threatening cardiac, CNS and respiratory adverse reactions.

If over-exposure occurs, call your Poison Control Center at 1-800-222-1222 for current information on the management of poisoning or overdosage.

Cardiac Effects

Symptoms

Cases of overdosage with loperamide hydrochloride (chronic ingestion of doses ranging from 70 mg to 1,600 mg daily; 4 times to 100 times the recommended dose) have resulted in life-threatening cardiac adverse reactions, including QT/QTc and QRS interval prolongation, Torsades de Pointes, Brugada syndrome and other ventricular arrhythmias, syncope, cardiac arrest, and death. Cases include patients who were abusing (using supratherapeutic doses in place of opioids to induce euphoria) or misusing (taking higher than recommended doses to control diarrhea or to prevent opioid withdrawal) loperamide. The following are representative cases that included cardiac adverse reactions:

• 25-year old abused loperamide and presented to the hospital on multiple occasions with symptoms of syncope, nausea, vomiting, bradycardia, hypotensive shock. The patient also experienced ventricular tachycardia, a prolonged QTc of 527 ms and QRS interval of 170 ms, frequent premature ventricular contractions, and subsequent cardiac arrest and death (elevated loperamide blood concentration of 32 ng/ml).
• 54-year old misused loperamide hydrochloride (up to 144 mg per day) as a self-treatment for chronic diarrhea for over 2 years. Signs of cardiac toxicity included syncope, prolonged QT of 500 ms sinus arrest with junctional escape rhythm, and polymorphic ventricular tachycardia, which required cardioversion and implantable cardioverter-defibrillator (ICD) management.
• 26-year old, with prior opioid abuse, presented to the hospital with recurrent syncope and developed Torsades de Pointes requiring electrical cardioversion. An ECG revealed a sinus rhythm with a heart rate of 85 bpm and a markedly prolonged QTc interval of greater than 700 ms. The patient reported ingesting 100 mg to 250 mg of loperamide hydrochloride with 400 mg of cimetidine daily for several months to simulate the euphoric sensation associated with opioids.

Management

Consider loperamide as a possible cause of cardiac arrhythmias in patients who may have a history of opioid abuse or recent ingestion of unknown drugs and in the differential diagnosis of unstable arrhythmias, prolonged QTc or QRS intervals, and Torsades de Pointes.

If loperamide-induced cardiac toxicity is suspected, promptly discontinue the drug and initiate therapy to manage and prevent cardiac arrhythmias and serious outcomes.

In many cases of loperamide overdosage, anti-arrhythmic medications (e.g., magnesium sulfate) were ineffective in resolving the arrhythmias and preventing further episodes of Torsades de Pointes. Electrical cardioversion and overdrive pacing, and isoproterenol continuous infusion were reported to manage QTc prolongation in the setting of overdose.

Laboratory Testing

Loperamide serum concentrations are not widely available or clinically useful to guide patient management.

CNS and Respiratory Depression

Symptoms

Cases of loperamide overdose (including relative overdose due to hepatic dysfunction), may cause opioid toxic effects including CNS depression (e.g. altered mental status, stupor, coordination disorders, somnolence, miosis, muscular hypertonia, respiratory depression), hypotension, urinary retention, and paralytic ileus. Pediatric patients may be more sensitive to CNS effects, including respiratory depression, than adults.

Management

Loperamide non-cardiac arrhythmia overdosages should be treated as opioid overdosages. Naloxone may reverse the opioid-related toxicity, including CNS and respiratory depression, and hypotension, associated with loperamide overdosage.

In adults and pediatric patients, naloxone may be administered intravenously. Appropriate doses of naloxone, via intranasal, intramuscular, intraosseus, or subcutaneous administration may be necessary if the intravenous route is not available. If the desired degree of opioid-related toxicity counteraction and improvement are not obtained, naloxone may be repeated at two- to three-minute intervals. If no response in opioid-related effects is observed after naloxone has been administered, then diagnosis of opioid-induced toxicity should be questioned.

Refer to the naloxone prescribing information for complete information on initial and subsequent dosages.

For patients whose adverse reactions are responsive to naloxone, monitor vital signs, neurologic and cardiopulmonary status for recurrence of opioid overdose symptoms for at least 24 hours after the last dose of naloxone, due to the prolonged intestinal retention of loperamide and the short duration (one to three hours) of naloxone. Patients with severe CNS or respiratory depression, and those who require multiple doses of naloxone to reverse symptoms, should be admitted to the hospital and may require intensive care.

Laboratory Testing

Standard drug screens for opioids do not include an assay for loperamide; such testing for opioids will yield negative results even in the presence of loperamide.

DOSAGE AND ADMINISTRATION

Loperamide hydrochloride capsules are contraindicated in pediatric patients less than 2 years of age due to the risks of respiratory depression and serious cardiac adverse reactions (seeCONTRAINDICATIONS).

Avoid loperamide hydrochloride capsules dosages higher than recommended in adult or pediatric patients 2 years of age and older due to the risk of serious cardiac adverse reactions (SeeWARNINGS andOVERDOSAGE).

(1 capsule = 2 mg) Patients should receive appropriate fluid and electrolyte replacement as needed.

Acute Diarrhea

Adults and Pediatric Patients 13 Years and Older: The recommended initial dose is 4 mg (two capsules) followed by 2 mg (one capsule) after each unformed stool. The maximum daily dose is 16 mg (eight capsules). Clinical improvement is usually observed within 48 hours.

Pediatric Patients 2 years to 12 Years of Age: In pediatric patients 2 years to 5 years of age (20 kg or less), the non-prescription liquid formulation of loperamide (1 mg/5 mL) should be used; for ages 6 to 12, either loperamide hydrochloride capsules or non-prescription liquid formulation of loperamide may be used. For pediatric patients 2 years to 12 years of age, the following schedule for capsules or liquid will usually fulfill initial dosage requirements:

Recommended First Day Dosage Schedule

Two to five years (13 kg to 20 kg): 1 mg three times daily (3 mg total daily dosage)

Six to eight years (20 kg to 30 kg): 2 mg twice daily (4 mg total daily dosage)

Eight to twelve years (greater than 30 kg): 2 mg three times daily (6 mg total daily dosage)

Recommended Subsequent Daily Dosage

Following the first treatment day, it is recommended that subsequent loperamide hydrochloride capsules doses (1 mg/10 kg body weight) be administered only after a loose stool. The total daily dosage should not exceed recommended dosages for the first day.

Chronic Diarrhea

Adults

The recommended initial dose is 4 mg (two capsules) followed by 2 mg (one capsule) after each unformed stool until diarrhea is controlled, after which the dosage of loperamide hydrochloride capsules should be reduced to meet individual requirements. When the optimal daily dosage has been established, this amount may then be administered as a single dose or in divided doses.

The average daily maintenance dosage in clinical trials was 4 mg to 8 mg (two to four capsules per day). The maximum daily dosage is 16 mg (eight capsules per day). If clinical improvement is not observed after treatment with 16 mg per day for at least 10 days, symptoms are unlikely to be controlled by further administration. Loperamide hydrochloride capsules administration may be continued if diarrhea cannot be adequately controlled with diet or specific treatment.

Elderly

No formal pharmacokinetic studies were conducted in elderly subjects. However, there were no major differences reported in the drug disposition in elderly patients with diarrhea relative to young patients. No dose adjustment is required for the elderly.

In general, elderly patients may be more susceptible to drug-associated effects of the QT interval. Avoid loperamide hydrochloride capsules in elderly patients taking drugs that can result in prolongation of the QT interval (for example, Class IA or III antiarrhythmics) or in patients with risk factors for Torsades de Pointes (seeWARNINGS).

Renal Impairment

No pharmacokinetic data are available in patients with renal impairment. Since the metabolites and the unchanged drug are mainly excreted in the feces, no dosage adjustment is required for patients with renal impairment (see PRECAUTIONS).

Hepatic Impairment

The pharmacokinetics of loperamide have not been studied in patients with hepatic impairment. Use loperamide hydrochloride capsules with caution in such patients because the systemic exposure may be increased due to reduced metabolism (seePRECAUTIONS).