Professional Information — Lomotil

Indications and Usage

Lomotil is indicated as adjunctive therapy in the management of diarrhea in patients 13 years of age and older.

Dosage and Administration

Management of Diarrhea in Patients 13 Years of Age and Older

Lomotil is recommended as adjunctive therapy for the management of diarrhea in patients 13 years of age and older. Consider the nutritional status and degree of dehydration in patients prior to initiating therapy with Lomotil. The use of Lomotil should be accompanied by appropriate fluid and electrolyte therapy, when indicated. If severe dehydration or electrolyte imbalance is present, do not administer Lomotil until appropriate corrective therapy has been indicated (see WARNINGS ).

Initial and Maximum Recommended Dosage in Patients 13 Years of Age and Older

The initial adult dosage is 2 Lomotil tablets four times daily (maximum total daily dose of 20 mg per day of diphenoxylate hydrochloride). Most patients will require this dosage until initial control of diarrhea has been achieved. Clinical improvement of acute diarrhea is usually observed within 48 hours.

Dosage after Initial Control of Diarrhea

After initial control has been achieved, the Lomotil dosage may be reduced to meet individual requirements. Control may often be maintained with as little as two Lomotil tablets daily.

Duration of Treatment

If clinical improvement of chronic diarrhea after treatment with the maximum recommended daily dosage is not observed within 10 days, discontinue Lomotil as symptoms are unlikely to be controlled by further administration.

Contraindications

Lomotil is contraindicated in:

• Pediatric patients less than 6 years of age due to the risks of respiratory and central nervous system (CNS) depression (see WARNINGS ).
• Patients with diarrhea associated with pseudomembranous enterocolitis (Clostridium difficile) or other enterotoxin-producing bacteria due to the risk of gastrointestinal (GI) complications, including sepsis (see WARNINGS ).
• Patients with known hypersensitivity to diphenoxylate or atropine.
• Patients with obstructive jaundice.

Adverse Reactions

The following serious adverse reactions are described elsewhere in labeling:

• Respiratory and/or CNS depression (see WARNINGS )
• Anticholinergic and opioid-toxicities, including atroponism (see WARNINGS and PRECAUTIONS )
• Dehydration and electrolyte imbalance (see WARNINGS )
• GI Complications in patients with infectious diarrhea (see WARNINGS )
• Toxic megacolon in patients with acute ulcerative colitis (see WARNINGS )

At therapeutic doses of Lomotil, the following other adverse reactions have been reported; they are listed in decreasing order of severity, but not of frequency:

Nervous system: numbness of extremities, euphoria, depression, malaise/lethargy, confusion, sedation/drowsiness, dizziness, restlessness, headache, hallucination

Allergic: anaphylaxis, angioneurotic edema, urticaria, swelling of the gums, pruritus

Gastrointestinal system: megacolon, paralytic ileus, pancreatitis, vomiting, nausea, anorexia, abdominal discomfort

The following adverse reactions related to atropine sulfate are listed in decreasing order of severity, but not of frequency: hyperthermia, tachycardia, urinary retention, flushing, dryness of the skin and mucous membranes.

Drug Interactions

Alcohol

Alcohol may increase the CNS depressant effects of Lomotil and may cause drowsiness (see WARNINGS ). Avoid concomitant use of Lomotil with alcohol.

Other Drugs that Cause CNS Depression

The concurrent use of Lomotil with other drugs that cause CNS depression (e.g., barbiturates, benzodiazepines, opioids, buspirone, antihistamines, muscle relaxants), may potentiate the effects of Lomotil (see WARNINGS ). Either Lomotil or the other interacting drug should be chosen, depending on the importance of the drug to the patient. If CNS-acting drugs cannot be avoided, monitor patients for CNS adverse reactions.

MAO Inhibitors

Diphenoxylate may interact with monoamine oxidase inhibitors (MAOIs) and precipitate a hypertensive crisis. Avoid use of Lomotil in patients who take MAOIs and monitor for signs and symptoms of hypertensive crisis (headache, hyperthermia, hypertension).

Drug Abuse and Dependence

Controlled substance

Lomotil is classified as a Schedule V controlled substance by federal regulation. Diphenoxylate hydrochloride is chemically related to the narcotic analgesic meperidine.

Drug abuse and dependence

In doses used for the treatment of diarrhea, whether acute or chronic, diphenoxylate has not produced addiction.

Diphenoxylate hydrochloride is devoid of morphine-like subjective effects at therapeutic doses. At high doses it exhibits codeine-like subjective effects. The dose which produces antidiarrheal action is widely separated from the dose which causes central nervous system effects. The insolubility of diphenoxylate hydrochloride in commonly available aqueous media precludes intravenous self-administration. A dose of 100 to 300 mg/day, which is equivalent to 40 to 120 tablets, administered to humans for 40 to 70 days, produced opiate withdrawal symptoms. Since addiction to diphenoxylate hydrochloride is possible at high doses, the recommended dosage should not be exceeded.

Overdosage

Diagnosis

Overdosage can be life-threatening. Symptoms of overdosage may include opioid and/or anticholinergic effects including respiratory depression, coma, delirium, lethargy, dryness of the skin and mucous membranes, mydriasis or miosis, flushing, hyperthermia, tachycardia, hypotonia, tachypnea, toxic encephalopathy, seizures and incoherent speech.

Respiratory depression has been reported up to 30 hours after ingestion and may recur despite an initial response to narcotic antagonists.

Treat all possible Lomotil overdosages as serious and maintain medical observation/hospitalization until patients become asymptomatic without naloxone use.

Treatment

A pure narcotic antagonist (e.g., naloxone) should be used in the treatment of respiratory depression caused by Lomotil. Refer to the prescribing information for naloxone. Consider Lomotil toxicity even in settings of negative toxicology tests.

Following initial improvement of respiratory function, repeated doses of naloxone hydrochloride may be required to counteract recurrent respiratory depression.

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

Description

Each Lomotil tablet contains:

2.5 mg of diphenoxylate hydrochloride USP (equivalent to 2.3 mg of diphenoxylate) and 0.025 mg of atropine sulfate USP (equivalent to 0.01 mg of atropine)

Diphenoxylate hydrochloride, an antidiarrheal, is ethyl 1-(3-cyano-3,3-diphenylpropyl)-4-phenylisonipecotate monohydrochloride and has the following structural formula:

Atropine sulfate, an anticholinergic, is endo-(±)-α-(hydroxymethyl) benzeneacetic acid 8-methyl-8-azabicyclo[3.2.1] oct-3-yl ester sulfate (2:1) (salt) monohydrate and has the following structural formula:

A subtherapeutic amount of atropine sulfate is present to discourage deliberate overdosage.

Inactive ingredients of Lomotil tablets include acacia, corn starch, magnesium stearate, sorbitol, sucrose, and talc.

Clinical Pharmacology

Diphenoxylate is rapidly and extensively metabolized in man by ester hydrolysis to diphenoxylic acid (difenoxine), which is biologically active and the major metabolite in the blood. After a 5 mg oral dose of carbon-14 labeled diphenoxylate hydrochloride in ethanolic solution was given to three healthy volunteers, an average of 14% of the drug plus its metabolites was excreted in the urine and 49% in the feces over a four-day period. Urinary excretion of the unmetabolized drug constituted less than 1% of the dose, and diphenoxylic acid plus its glucuronide conjugate constituted about 6% of the dose. In a 16-subject crossover bioavailability study, a linear relationship in the dose range of 2.5 to 10 mg was found between the dose of diphenoxylate hydrochloride (given as Lomotil liquid) and the peak plasma concentration, the area under the plasma concentration-time curve, and the amount of diphenoxylic acid excreted in the urine. In the same study the bioavailability of the tablet compared with an equal dose of the liquid was approximately 90%. The average peak plasma concentration of diphenoxylic acid following ingestion of four 2.5 mg tablets was 163 ng/ml at about 2 hours, and the elimination half-life of diphenoxylic acid was approximately 12 to 14 hours.

In dogs, diphenoxylate hydrochloride has a direct effect on circular smooth muscle of the bowel that conceivably results in segmentation and prolongation of gastrointestinal transit time. The clinical antidiarrheal action of diphenoxylate hydrochloride may thus be a consequence of enhanced segmentation that allows increased contact of the intraluminal contents with the intestinal mucosa.

How Supplied / Storage and Handling

Tablets — round, white, with SEARLE debossed on one side and 61 on the other side and containing 2.5 mg of diphenoxylate hydrochloride and 0.025 mg of atropine sulfate, supplied as:

Store below 25°C (77°F).

Patient Counseling Information

Advise patients:

• Accidental ingestion of Lomotil in children, especially in those less than 6 years of age, may result in severe respiratory depression or coma. Instruct patients to take steps to store Lomotil securely and out of reach of children, and to dispose of unused Lomotil (see WARNINGS ).
• To take Lomotil at the prescribed dosage. Use of a higher than prescribed dosage may include opioid and/or anticholinergic effects (see OVERDOSAGE ). Report to a healthcare facility if they develop anticholinergic symptoms such as hyperthermia, flushing, tachycardia, tachypnea, hypotonia, lethargy, hallucinations, febrile convulsion, dry mouth, mydriasis or opioid symptoms such as progressive CNS and respiratory depression, miosis, seizures, or paralytic ileus.
• Lomotil may produce drowsiness or dizziness. Concomitant use of alcohol or other drugs that also cause CNS depression (e.g., barbiturates, benzodiazepines, opioids, buspirone, antihistamines, and muscle relaxants) may increase this effect. Inform patients not to operate motor vehicles or other dangerous machinery until they are reasonably certain that Lomotil does not affect them adversely.
• To use fluid and electrolyte therapy, if prescribed along with Lomotil, as instructed by their healthcare provider.
• Clinical improvement of diarrhea is usually observed within 48 hours. If clinical improvement is not seen within 10 days, discontinue Lomotil and contact their healthcare provider.