Dicyclomine vs. Donnatal

• Dicyclomine and Donnatal (belladonna/phenobarbital) are used to treat irritable bowel syndrome (IBS).
• Dicyclomine and Donnatal belong to different drug classes. Dicyclomine is an anticholinergic and Donnatal is a combination of an anticholinergic/antispasmodic.
• A brand name for dicyclomine is Bentyl.
• Side effects of dicyclomine and Donnatal that are similar include dry mouth, blurred vision, increased heart rate, heart palpitations, constipation, difficulty urinating, headache, nervousness, drowsiness, and dizziness.
• Side effects of dicyclomine that are different from Donnatal include confusion, agitation, seizures, changes in taste, difficulty swallowing, weakness, impotence, flushing, delirium, difficulty falling asleep (insomnia), nausea, vomiting, rash, skin redness, fainting, bloating, and difficulty breathing.
• Side effects of Donnatal that are different from dicyclomine include dry eyes.

Dicyclomine is an anticholinergic used to treat irritable bowel syndrome (IBS). Anticholinergic drugs block the effects of acetylcholine, the chemical transmitter that nerves release in order to cause muscles to contract. They prevent contraction of muscles by blocking the acetylcholine receptors on the muscle cells. Anticholinergic drugs also have a direct relaxing effect on muscle. Dicyclomine is used to reduce contraction of the muscles in the intestines.

Donnatal (belladonna/phenobarbital) is a combination of an anticholinergic/antispasmodic drug and a barbiturate sedative used to treat symptoms of abdominal pain, bloating, and cramps in patients with irritable bowel syndrome (IBS). Donnatal is also used to treat acute inflammation of the stomach and intestines (gastroenteritis) to reduce pain and diarrhea, and in patients with duodenal ulcer. Belladonna alkaloids block the action of acetylcholine, a chemical that nerves to use to communicate with other nerves and muscles. Acetylcholine stimulates the muscles of the intestines that propels digesting food through the intestine. It also affects the secretion of fluids by salivary glands and the stomach. By blocking acetylcholine, belladonna alkaloids relax intestinal muscles, slow passage of digesting food through the intestines, and reduce gastric secretion. Phenobarbital produces sedation.

Dicyclomine

Common side effects include:

• dry mouth (xerostomia),
• blurred vision,
• confusion,
• agitation,
• increased heart rate,
• heart palpitations,
• constipation,
• difficulty urinating, and
• seizures.

Other important side effects include:

• changes in taste perception,
• difficulty swallowing,
• headache, nervousness,
• drowsiness,
• weakness,
• dizziness,
• impotence,
• flushing,
• delirium,
• difficulty falling asleep,
• nausea,
• vomiting,
• rash,
• erythema,
• fainting,
• bloating, and
• difficulty breathing.

Donnatal

Adverse reactions include:

• constipation;
• dry eyes;
• dry mouth;
• urinary hesitancy and retention (difficulty urinating, particularly in men);
• blurred vision;
• rapid heart rate;
• palpitations;
• headache;
• nervousness;
• drowsiness; and
• dizziness

Caution is advised in patients with glaucoma, myasthenia gravis and urinary obstruction since symptoms of these conditions may worsen with the use of belladonna/phenobarbital. Patients with an unstable cardiac status, severe ulcerative colitis and acute intermittent porphyria should avoid belladonna/phenobarbital. Elderly patients may experience confusion, depression, and excitement even from small doses.

Dicyclomine

The recommended starting oral dose of dicyclomine is 20 mg given 4 times daily. The dose can be increased to 40 mg 4 times daily. The recommended intramuscular injection is 10 to 20 mg 4 times daily. The intramuscular injection is only used for 1 to 2 days if a patient cannot take capsules or tablets.

Donnatal

May be taken with or without food. The dosage is adjusted to the individual patient to assure control of symptoms with a minimum of side effects. The usual doses are 1-2 regular tablets 3 to 4 times daily or 1 extended release tablet every 8 or 12 hours or 5-10 ml of the elixir, 3 or 4 times daily.

Dicyclomine

Antiglaucoma Agents

Anticholinergics antagonize the effects of antiglaucoma agents and may increase intraoccular pressure. Anticholinergic drugs in the presence of increased intraocular pressure may be hazardous when taken concurrently with agents such as corticosteroids. Use of Bentyl in patients with glaucoma is not recommended.

Other Drugs with Anticholinergic Activity

The following agents may increase certain actions or side effects of anticholinergic drugs including Bentyl:

• amantadine,
• antiarrhythmic agents of Class I (for example, quinidine),
• antihistamines,
• antipsychotic agents (for example, phenothiazines),
• benzodiazepines,
• MAO inhibitors,
• narcotic analgesics (for example, meperidine),
• nitrates and nitrites,
• sympathomimetic agents,
• tricyclic antidepressants, and
• other drugs having anticholinergic activity.

Other Gastrointestinal Motility Drugs

Interaction with other gastrointestinal motility drugs may antagonize the effects of drugs that alter gastrointestinal motility, such as metoclopramide.

Effect of Antacids

Because antacids may interfere with the absorption of anticholinergic agents including Bentyl, simultaneous use of these drugs should be avoided.

Effect on Absorption of Other Drugs

Anticholinergic agents may affect gastrointestinal absorption of various drugs by affecting on gastrointestinal motility, such as slowly dissolving dosage forms of digoxin; increased serum digoxin concentration may result.

Effect on Gastric Acid Secretion

The inhibiting effects of anticholinergic drugs on gastric hydrochloric acid secretion are antagonized by agents used to treat achlorhydria and those used to test gastric secretion.

Donnatal

Phenobarbital reduces the blood levels of several drugs by increasing their breakdown in the body. Examples include voriconazole (Vfend), bocepravir (Victrelis), ranolazine (Ranexa), and protease inhibitors (for example, atazanavir [Reyataz], indinavir [Crixivan], saquinavir [Invirase], ritonavir [Norvir]). Belladonna/phenobarbital should not be combined with potassium tablets because belladonna/phenobarbital slows the passage of potassium tablets through the gastrointestinal tract, leading to potassium-induced ulcers and high potassium levels in the blood.

Dicyclomine

There are no adequate studies of the effect of dicyclomine in pregnant women at recommended doses (80-160 mg/day). Observation of women who received dicyclomine (up to 40 mg/day) containing products during the first trimester of pregnancy did not reveal any increased risk of harm to the fetus.

Dicyclomine is excreted into breast milk. Since there have been reports of apnea (cessation of breathing) when dicyclomine has been given to children, it should not be used by nursing mothers.

Donnatal

Use during pregnancy has not been adequately evaluated. Pregnant women should use belladonna alkaloid/phenobarbital only when the expected benefit outweighs the potential but unknown risks. Belladonna/phenobarbital are secreted in breast milk and may also reduce milk production.