Spasmolytic & Antispasmodic Drugs
Key Points
- Medications that relieve smooth muscle spasm
- Used in gastrointestinal, genitourinary, and respiratory conditions
- Multiple mechanisms of action
- Require careful dosing in pediatric population
- Important role in functional gastrointestinal disorders
Classification by Mechanism
- Anticholinergics (Antimuscarinic agents)
- Direct smooth muscle relaxants
- Calcium channel blockers
- Nitric oxide donors
- Natural/herbal preparations
Major Drug Classes
Anticholinergic Agents
- Dicyclomine
- Mechanism: Selective M1 antagonist
- Primary use: Intestinal spasms
- Contraindicated <6 months
- Hyoscyamine
- Mechanism: Nonselective muscarinic antagonist
- Uses: GI spasms, bladder spasms
- Available in multiple formulations
- Glycopyrrolate
- Mechanism: Long-acting antimuscarinic
- Uses: Chronic secretions, drooling
- Limited GI tract absorption
Direct Smooth Muscle Relaxants
- Mebeverine
- Direct action on smooth muscle
- No significant anticholinergic effects
- Used in IBS and functional abdominal pain
- Papaverine
- Phosphodiesterase inhibitor
- Non-narcotic smooth muscle relaxant
- Limited pediatric use
Calcium Channel Blockers
- Peppermint oil
- Natural calcium channel blocker
- Local effect on GI smooth muscle
- Available in enteric-coated forms
Clinical Applications
Gastrointestinal Disorders
- Functional Abdominal Pain
- First-line: Peppermint oil
- Second-line: Dicyclomine/Hyoscyamine
- Irritable Bowel Syndrome
- Acute symptoms: Antispasmodics
- Chronic management: Dietary modification
- Infantile Colic
- Limited role for medications
- Focus on non-pharmacological approaches
Genitourinary Conditions
- Neurogenic Bladder
- Bladder Spasms
- Post-surgical management
- Chronic conditions
Respiratory Applications
- Bronchial Spasms
- Limited role compared to bronchodilators
- Adjunctive therapy in select cases
Administration and Dosing
Dicyclomine
- Age Restrictions: >6 months
- Dosing:
- 6mo-2yrs: 5-10mg TID-QID
- 2-12yrs: 10mg TID-QID
- >12yrs: 20mg QID
Hyoscyamine
- Pediatric Dosing:
- 2-12yrs: 0.0625-0.125mg q4h
- >12yrs: 0.125-0.25mg q4h
- Available Forms:
- Sublingual tablets
- Oral solution
- Extended-release tablets
Glycopyrrolate
- Oral Dosing:
- 3-16yrs: 0.02-0.04mg/kg/dose TID
- Maximum: 2mg/dose
Clinical Considerations
Adverse Effects
- Anticholinergic Effects
- Dry mouth
- Blurred vision
- Urinary retention
- Constipation
- Tachycardia
- Central Effects
- Drowsiness
- Confusion
- Agitation
Monitoring Requirements
- Clinical Response
- Symptom improvement
- Side effect assessment
- Quality of life measures
- Safety Parameters
- Heart rate
- Mental status
- Bladder/bowel function
- Vision changes
Contraindications
- Absolute:
- Infants <6 months (dicyclomine)
- Pyloric stenosis
- Myasthenia gravis
- Narrow-angle glaucoma
- Relative:
- Autonomic neuropathy
- Severe ulcerative colitis
- Hepatic/renal impairment
Further Reading
