Butylscopolamine and Trimebutine Hydroxide

Mechanism

🚫 Butylscopolamine

• Class: Anticholinergic derived from quaternary ammonium.
• BBB profile: The permanent positive charge of the quaternary ammonium group completely prevents its passage through the blood-brain barrier.
• CNS effects: Lacks the central sedative, confusional, or psychotropic effects characteristic of atropine or tertiary scopolamine.

🧬 Trimebutin

• Class: Mixed spectrum motility modulator and spasmolytic.
• Dual mechanism: Acts as a weak agonist of peripheral µ, κ and δ opioid receptors, selectively modulating intestinal contraction in hyperkinetic and hypokinetic states.

Mechanism of action

Butylscopolamine: It acts as a competitive antagonist of muscarinic acetylcholine receptors, specifically the M₃ type located in smooth muscle fibers and cells of the secretory glands of the gastrointestinal tract. This muscarinic blockade inhibits acetylcholine-induced contraction of the vagus nerve and decreases spasm of the hollow viscera, reducing colicky pain and decreasing glandular hypersecretion.

Trimebutin: It exerts a unique dual modulation at the enteric level:

• In cases of hypermotility (spasm or diarrhea), trimebutine acts through presynaptic κ- and δ-opioid receptors, inhibiting excessive release of acetylcholine and relieving spasmodic pain.
• In cases of hypomotility (constipation or ileus), it behaves as an agonist of neuronal µ receptors and stimulates the coordinated release of acetylcholine, normalizing colonic transit.
• It also blocks voltage-activated sodium and calcium channels in smooth muscle fiber, enhancing its visceral antinociceptive effect.

Indicators and dose

Approved indications

• Butylscopolamine: Relief of acute spasms of the gastrointestinal, biliary or urinary tract (renal colic, biliary colic). Differential diagnosis of muscle spasms in radiology and endoscopy.
• Trimebutin: Symptomatic treatment of irritable bowel syndrome (IBS) and functional dyspepsia associated with digestive motor disorders.

Dosage and Clinical Adjustment

Butylscopolamine:

• Acute spasm (parenteral IV/IM): 20 mg to 40 mg of butylscopolamine bromide slowly intravenously or deep intramuscularly. Do not exceed the maximum daily dose of 100 mg.
• Oral use: 10 mg to 20 mg orally three to five times a day, with plenty of water.

Trimebutin:

• 100 mg to 200 mg orally three times a day, preferably administered before main meals for up to 4 weeks.

Adjustments in Deficiencies:

• Butylscopolamine: Close caution in elderly people with renal dysfunction due to increased risk of urine retention or hidden tachyarrhythmias.
• Trimebutin: Does not require major dose adjustments in mild to moderate renal failure.

Security

Contraindications

• Butylscopolamine (Absolutes): Hypersensitivity to quaternary ammonium. Untreated narrow-angle glaucoma (pupillary muscarinic block dilates the pupil and can trigger acute attacks of blindness). Benign prostatic hypertrophy with active urinary retention (muscarinic blockade of the detrusor muscle of the bladder prevents urination). Myasthenia gravis. Megacolon or active mechanical intestinal obstruction.
• Trimebutin (Absolutes): Hypersensitivity to trimebutine.

Adverse effects (ADRs)

• Butylscopolamine (Peripheral anticholinergics): Dry mouth (xerostomia), mydriasis with blurred vision, compensatory sinus tachycardia, facial flushing due to anhidrosis, secondary constipation, urine retention.
• Trimebutin: Mild dry mouth, transient dizziness, unusual drowsiness, rare skin rashes.

Pregnancy and Safety of Use

Butylscopolamine: Category C. Although animal teratogenesis has not been demonstrated, the use of injectable preparations should be avoided in the first trimester. Its use at the end of pregnancy can alter the fetal heart rate due to reflex tachycardia.

Trimebutin: It is routinely discouraged during the first trimester due to the lack of large-scale controlled studies, using it only if clinical benefits outweigh therapeutic doubts.