Dicyclomine

Usage

Dicyclomine is prescribed for the treatment of functional bowel disorders, particularly irritable bowel syndrome (IBS). It alleviates symptoms like abdominal cramping and pain associated with these conditions. Its pharmacological classification is anticholinergic/antispasmodic. Dicyclomine works by slowing down the natural movements of the gastrointestinal tract and relaxing the muscles in the stomach and intestines.

Alternate Names

Dicyclomine is also known as dicycloverine. A popular brand name for dicyclomine is Bentyl.

How It Works

Pharmacodynamics: Dicyclomine acts as an anticholinergic agent, primarily targeting muscarinic receptors (M1, M2, and M3) in the smooth muscles of the gastrointestinal tract. This leads to reduced motility and spasm relief. It also exhibits some antihistaminic and antibradykinin effects.

Pharmacokinetics: Dicyclomine is well-absorbed after oral administration, reaching peak plasma concentrations in 1 to 1.5 hours. It is primarily metabolized in the liver and excreted in the urine.

Mode of Action: The drug non-competitively inhibits the actions of acetylcholine, histamine, and bradykinin on the smooth muscles of the gut, causing relaxation and decreased motility.

Elimination Pathways: Dicyclomine is mainly excreted through the renal system (kidneys) after hepatic metabolism.

Dosage

Standard Dosage

Adults:

Initial dose: 20 mg orally four times a day. This may be increased to 40 mg orally four times a day after one week if symptoms persist and side effects are tolerable. The maximum recommended dose is 160 mg per day. For intramuscular administration (when oral route is not feasible): 10-20 mg every 6 hours, not to exceed 80 mg/day. IM use should be limited to 1-2 days.

Children:

Infants >6 months (off-label): 5 mg orally three to four times a day. Maximum: 20 mg/day orally.

Children (off-label): 10 mg orally three to four times a day. Maximum: 40 mg/day orally.

Administer 30-60 minutes before meals.

Special Cases:

• Elderly Patients: Start with a lower dose (e.g., 10-20 mg orally every six hours) and titrate cautiously due to increased risk of adverse effects. Do not exceed 160 mg/day. Avoid IM administration.

• Patients with Renal Impairment: Dose adjustment may be necessary. Monitor renal function.

• Patients with Hepatic Dysfunction: Dose adjustment may be necessary due to potential changes in drug metabolism.

• Patients with Comorbid Conditions: Careful consideration is needed, particularly with conditions like glaucoma, myasthenia gravis, urinary retention, and cardiovascular disease.

Clinical Use Cases

Dicyclomine’s clinical use is primarily focused on managing IBS symptoms. It is not typically indicated for intubation, surgical procedures, mechanical ventilation, ICU use, or emergency situations.

Dosage Adjustments

Dose adjustments may be necessary based on patient response, side effects, renal or hepatic dysfunction, and other concomitant medical conditions.

Side Effects

Common Side Effects:

Dry mouth, dizziness, blurred vision, nausea, drowsiness, weakness, nervousness, constipation, and abdominal bloating.

Rare but Serious Side Effects:

Allergic reactions (rash, itching, swelling), difficulty breathing, rapid heartbeat, confusion, hallucinations, difficulty urinating, and heat stroke (due to decreased sweating).

Long-Term Effects:

Chronic complications from long-term dicyclomine use are not well-established, but potential concerns include worsening of pre-existing conditions like glaucoma and urinary retention.

Adverse Drug Reactions (ADR):

Severe allergic reactions (anaphylaxis), cardiac arrhythmias, and paralytic ileus require urgent medical attention.

Contraindications

Absolute contraindications include: Hypersensitivity to dicyclomine, glaucoma (especially angle-closure), myasthenia gravis, paralytic ileus, gastrointestinal obstruction, urinary retention, unstable cardiovascular status in acute hemorrhage, infants younger than six months old, and breastfeeding mothers.

Drug Interactions

Dicyclomine interacts with numerous medications. Clinically significant interactions can occur with:

• Other anticholinergic drugs (additive anticholinergic effects): Antihistamines, antipsychotics, tricyclic antidepressants.

• Drugs affecting GI motility: Metoclopramide (decreased efficacy of metoclopramide).

• Drugs metabolized by CYP450 enzymes: Dicyclomine can inhibit the metabolism of certain drugs like digoxin, increasing their levels and risk of toxicity.

• Antacids (reduced absorption of dicyclomine): Take antacids after meals and dicyclomine before meals.

• Alcohol (increased sedation and drowsiness).

Pregnancy and Breastfeeding

Pregnancy Safety Category: B (animal studies show no risk, but human studies are limited). Use only if clearly needed and under careful medical supervision. Dicyclomine is contraindicated in breastfeeding mothers as it is excreted in breast milk and can cause adverse effects in infants.

Drug Profile Summary

• Mechanism of Action: Anticholinergic/antispasmodic; inhibits muscarinic receptors and actions of acetylcholine, histamine, and bradykinin.
• Side Effects: Dry mouth, dizziness, blurred vision, nausea, drowsiness, constipation. Serious side effects: Allergic reactions, cardiac arrhythmias, paralytic ileus, heat stroke.
• Contraindications: Glaucoma, myasthenia gravis, paralytic ileus, GI obstruction, urinary retention, infants <6 months, breastfeeding.
• Drug Interactions: Other anticholinergics, metoclopramide, digoxin, antacids, alcohol.
• Pregnancy & Breastfeeding: Pregnancy Category B; contraindicated while breastfeeding.
• Dosage: Adults: 20-40 mg orally four times a day (max 160 mg/day). Children (off-label): Dose based on age and weight; refer to pediatric dosage guidelines.
• Monitoring Parameters: Monitor for adverse effects, especially in elderly patients.

Popular Combinations

While dicyclomine can be used in combination with other medications to treat IBS, specific “popular” combinations are not widely established. The use of combination therapy should be individualized based on patient needs and potential drug interactions.

Precautions

• General Precautions: Assess for allergies, pre-existing medical conditions (glaucoma, myasthenia gravis, cardiovascular disease, etc.), and concomitant medications.
• Specific Populations: Use with caution in elderly patients and those with renal or hepatic impairment. Contraindicated in infants <6 months and breastfeeding mothers.
• Lifestyle Considerations: Avoid alcohol and activities requiring mental alertness. Take precautions in hot weather to avoid heatstroke.

FAQs (Frequently Asked Questions)

Q1: What is the recommended dosage for Dicyclomine?

A: Adults: Initial dose is 20 mg orally four times a day, which can be increased to 40 mg four times daily (maximum 160 mg/day). Pediatric dosages are off-label and require careful consideration of age and weight. Refer to the dosage section for details.

Q2: What are the common side effects of Dicyclomine?

A: Common side effects include dry mouth, blurred vision, dizziness, drowsiness, nausea, constipation, and abdominal bloating.

Q3: How does Dicyclomine work?

A: Dicyclomine is an anticholinergic and antispasmodic drug that blocks the action of acetylcholine and other mediators, leading to relaxation of the smooth muscles in the gastrointestinal tract.

Q4: Who should not take Dicyclomine?

A: Patients with glaucoma, myasthenia gravis, paralytic ileus, urinary retention, or infants under 6 months old should not take dicyclomine. Breastfeeding mothers should also avoid the drug.

Q5: What are the serious side effects of Dicyclomine?

A: Serious side effects include allergic reactions, rapid heartbeat, confusion, hallucinations, difficulty urinating, and heat stroke. Seek immediate medical attention if these occur.

Q6: Can Dicyclomine be used during pregnancy?

A: Dicyclomine is classified as Pregnancy Category B. While animal studies haven’t shown risk, human data is limited. Use only if clearly needed and under close medical supervision.

Q7: Does Dicyclomine interact with other medications?

A: Yes, dicyclomine can interact with other anticholinergic drugs, metoclopramide, digoxin, antacids, and alcohol. Inform your doctor about all medications and supplements you are taking.

Q8: What is Dicyclomine used for?

A: Dicyclomine is primarily used to treat the symptoms of irritable bowel syndrome (IBS), such as abdominal pain and cramping.

Q9: How should Dicyclomine be taken?

A: Dicyclomine is typically taken orally, 30-60 minutes before meals. It is also available as an intramuscular injection, but this route is generally reserved for short-term use when oral administration is not possible.