GENERIC NAME: diphenoxylate and atropine

BRAND NAME: Lomotil

DRUG CLASS AND MECHANISM: Lomotil is a combination of two drugs, diphenoxylate and atropine. It is used to treat acute diarrhea (diarrhea of limited duration). Diphenoxylate is a man-made narcotic chemically related to meperidine (Demerol). Diphenoxylate reduces diarrhea by interfering with the propulsion of intestinal contents through the intestines. Although diphenoxylate is chemically related to narcotics, it does not have pain- relieving (analgesic) actions like most other narcotics. In higher doses, However, like other narcotics, diphenoxylate can cause euphoria (elevation of mood) and physical dependence. In order to prevent abuse of diphenoxylate for its mood-elevating effects, atropine is combined with diphenoxylate in small quantities. As a result, if Lomotil is taken in greater than recommended doses unpleasant side effects from too much atropine will occur. Lomotil was approved by the FDA in 1960.

PRESCRIPTION: yes

GENERIC AVAILABLE: yes

PREPARATIONS: tablets (2.5mg diphenoxylate and 0.025mg atropine); liquid (2.5mg diphenoxylate and 0.025mg atropine per teaspoonsful).

STORAGE: Store at room temperature, 15-30°C (59- 86°F).

PRESCRIBED FOR: Lomotil is used for the relief of acute diarrhea.

DOSING: In adults, the usual dose is 5 mg (2 tablets) three to four times per day initially. Thereafter, the dose may be decreased to 2.5mg (1 tablet) two to three times a day. The dose for children is based on weight. If diarrhea is not better within 48 hours, diphenoxylate is not likely to be effective with more prolonged treatment.

DRUG INTERACTIONS:

Reduced effectiveness: The combination of diphenoxylate and monoamine oxidase inhibitors (MAO's) - for example, isocarboxazid (Marplan), phenelzine (Nardil), tranylcypromine (Parnate), and procarbazine (Matulane)] - can cause severe high blood pressure with the possibility of a cerebrovascular accident (stroke).

Constipation: Drugs which increase the propulsion of intestinal contents theoretically can reduce the effectiveness of diphenoxylate. Such drugs include bethanechol (Urecholine), cisapride (Propulsid), metoclopramide (Reglan), and erythromycin. Drugs which decrease the propulsion of intestinal contents may exaggerate the effects of diphenoxylate and cause constipation. Such drugs include hyoscyamine (Levsin; Cystospaz), antihistamines such as hydroxyzine (Vistaril, Atarax) and diphenhydramine (Benadryl), opiate agonists such as oxycodone (Percocet), hydrocodone (Vicodin), some phenothiazine antipsychotics such as chlorpromazine (Thorazine), thioridazine (Mellaril), triflupromazine (Stelazine), and some tricyclic antidepressants such as amitriptyline (Elavil), amoxapine (Asendin), clomipramine (Anafranil), doxepin (Sinequan), imipramine (Tofranil), nortriptyline (Pamelor), protriptyline (Vivactil), and trimipramine (Surmontil).

Sedation: Taking diphenoxylate with ethanol or other chemicals or medications that can depress the central nervous system may cause excessive sedation. Such drugs include barbiturates, benzodiazepines, for example, lorazepam (Ativan), diazepam (Valium), temazepam (Restoril), oxazepam (Serax), or clonazepam (Klonopin)], zolpidem (Ambien), narcotics, and tricyclic antidepressants (listed above).

PREGNANCY: Adequate studies of diphenoxylate in pregnant women have not been done, so diphenoxylate should be used during pregnancy only when clearly needed.

NURSING MOTHERS: Diphenoxylic acid, a metabolite of diphenoxylate (that is, diphenoxylate that has been changed chemically by the body) is excreted into breast milk, as is atropine. Although there have not been problems reported in the infants of women who breast-feed, the benefits to the mother should be weighed against the potential risks to the nursing infant.

SIDE EFFECTS: The most common side effects reported in persons taking diphenoxylate include drowsiness (1 in 25), dizziness (1 in 20), and headache (1 in 40), nausea or vomiting (between 1 in 30 and 1 in 14), and dry mouth (1 in 30). Euphoria, depression, lethargy, restlessness, numbness of extremities, loss of appetite, and abdominal pain or discomfort have been reported less frequently.

Although the dose of atropine in Lomotil is too low to cause side effects when taken in the recommended doses, side effects of atropine (including dryness of the skin and mucous membranes, increased heart rate, urinary retention, and increased body temperature) have been reported, particularly in children under 2 years of age and children with Down's syndrome.

Reference: FDA Prescribing Information

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