Antispasmodics

Antispasmodics are a group of medications used to relieve or prevent muscle spasms, which are involuntary and often painful contractions of muscles. These drugs primarily target smooth muscle spasms found in the gastrointestinal (GI) tract, bladder, uterus, or other internal organs, as well as occasionally in skeletal muscles.

Antispasmodics are a group of medications used to reduce excessive GI smooth muscle contractility and spasm. These medications may be helpful in those with abdominal pain due to conditions such as irritable bowel syndrome , although their efficacy is controversial. Antispasmodics are classified based on their action; they include anticholinergics and direct smooth muscle relaxants. Anticholinergics block muscarinic receptor activity in the enteric nervous system and on smooth muscle cells, but can also have systemic anticholinergic side effects (e.g., urinary retention , blurred vision , xerostomia , tachycardia ). Direct smooth muscle relaxants have a variety of potential effects, but notably, they act directly on smooth muscle cells. These medications are not associated with anticholinergic side effects.

What are Antispasmodics Used for?

You might take antispasmodics to help treat spasms in your abdominal or urinary organs, including:

• Irritable bowel syndrome (IBS).
• Colon spasms.
• Functional dyspepsia.
• Menstrual cramps.
• Biliary colic.
• Gallbladder pain.
• Pancreatitis.
• Overactive bladder.

Healthcare providers also use antispasmodics in medical procedures. They might give you the medication as an injection before your procedure to help relax you and sedate your digestive system.

How Antispasmodics Work

Antispasmodics act by relaxing the smooth muscles of internal organs or interfering with nerve signals that cause spasms. Their effects can vary depending on the underlying condition and the drug type. Antispasmodics work by reducing or preventing muscle spasms, which are involuntary and often painful contractions of muscles. These drugs primarily target smooth muscle (involuntary muscles found in internal organs like the stomach, intestines, and bladder). Their mechanism of action depends on the specific type of antispasmodic.

1. Anticholinergic Antispasmodics

These drugs block the action of acetylcholine, a neurotransmitter that stimulates smooth muscle contractions. By inhibiting acetylcholine, they reduce the spasms and overactivity of smooth muscles.

• How They Work:
  • Block muscarinic receptors in the smooth muscle.
  • Reduce parasympathetic nerve activity, which controls involuntary muscle contractions.
  • Result: Relaxation of smooth muscles, reduced secretions, and slower movement in the affected organs.
• Examples:
  • Dicyclomine (Bentyl): Used for irritable bowel syndrome (IBS).
  • Hyoscyamine: Reduces intestinal and bladder spasms.
  • Propantheline: Treats hypermotility disorders of the GI tract.

2. Direct Smooth Muscle Relaxants

These drugs act directly on the smooth muscles themselves to relax them. They do not interfere with nerve signals but instead modify the muscle’s ability to contract.

• How They Work:
  • Alter ion channels (e.g., calcium channels) to reduce muscle contractility.
  • Reduce the muscle’s response to stimuli, leading to relaxation.
  • Result: Direct relief of spasms without affecting nerve activity.
• Examples:
  • Mebeverine: Commonly used for IBS.
  • Alverine Citrate: Relieves abdominal cramping and discomfort.

3. Other Mechanisms

Certain antispasmodics use unique mechanisms depending on their target organ or application:

• Beta-3 Adrenergic Agonists (e.g., Mirabegron):
  • Work on beta-3 receptors in the bladder to reduce spasms and increase bladder capacity.
• Calcium Channel Modulators:
  • Decrease calcium influx into smooth muscle cells, reducing contractions.

Types of Antispasmodics

Antispasmodics can be classified into two main categories:

1. Gastrointestinal (GI) Antispasmodics

These are used to relieve spasms and cramping in the stomach and intestines. Commonly prescribed for conditions like Irritable Bowel Syndrome (IBS) and abdominal pain.

• Anticholinergic Antispasmodics: Block acetylcholine, reducing muscle contractions and secretions.
  • Examples:
    • Dicyclomine (Bentyl)
    • Hyoscyamine (Levsin)
    • Propantheline
• Direct-Acting Smooth Muscle Relaxants: Act directly on smooth muscle to relieve spasms.
  • Examples:
    • Mebeverine (used in IBS)
    • Alverine Citrate

2. Urinary Antispasmodics

These are used to manage conditions like overactive bladder (OAB) or urinary incontinence by relaxing bladder muscles.

• Examples:
  • Oxybutynin (Ditropan)
  • Tolterodine (Detrol)
  • Mirabegron (Myrbetriq)

Antispasmodics Medication List

Here is a comprehensive list of antispasmodic medications, grouped by their primary use and mechanism of action:

1. Gastrointestinal Antispasmodics

These are used to treat intestinal and stomach spasms, such as those caused by irritable bowel syndrome (IBS) or other gastrointestinal disorders.

Anticholinergic Agents

• Dicyclomine (Bentyl): Relieves spasms in the GI tract, commonly used for IBS.
• Hyoscyamine (Levsin, Levbid): Reduces intestinal spasms and controls secretions.
• Propantheline: Used for hypermotility disorders and peptic ulcers.
• Clidinium (often combined with chlordiazepoxide as Librax): Relieves anxiety and spasms in IBS and ulcers.

Direct-Acting Smooth Muscle Relaxants

• Mebeverine: Frequently prescribed in Europe and Asia for IBS and functional bowel disorders.
• Alverine Citrate: Used for abdominal cramping and GI spasms.
• Pinaverium: Treats IBS and other bowel disorders by reducing smooth muscle activity.
• Trimebutine: Modulates smooth muscle contractions, commonly used for GI disorders.

2. Urinary Antispasmodics

These drugs target bladder spasms and help manage overactive bladder (OAB) or urinary incontinence.

Anticholinergic Agents

• Oxybutynin (Ditropan, Oxytrol): Reduces bladder muscle spasms and treats OAB.
• Tolterodine (Detrol): Alleviates urinary urgency and frequency.
• Solifenacin (Vesicare): Specifically targets bladder muscle spasms.
• Darifenacin (Enablex): Treats urinary incontinence.
• Fesoterodine (Toviaz): Effective for bladder overactivity.

Beta-3 Adrenergic Agonists

• Mirabegron (Myrbetriq): Relaxes the bladder muscle by activating beta-3 receptors.

3. Gynecological Antispasmodics (Menstrual Cramps)

These drugs help relieve uterine muscle spasms during menstruation.

• Hyoscine Butylbromide (Buscopan): Widely used for menstrual pain and other smooth muscle cramps.
• Naproxen (an NSAID, not a true antispasmodic): Reduces uterine spasms by lowering prostaglandin levels.

4. Biliary, Respiratory, and Other Smooth Muscle Spasms

• Papaverine: Treats smooth muscle spasms in the biliary tract or blood vessels.
• Nitroglycerin: Occasionally used for esophageal spasms or anal fissures.
• Phloroglucinol (Spasfon): Common in Europe for spasms in the GI and biliary systems.

5. Combination Antispasmodic Medications

These combine antispasmodic drugs with other agents for enhanced effects:

• Donnatal: A combination of phenobarbital, hyoscyamine, atropine, and scopolamine, used for IBS and GI conditions.
• Librax: A mix of clidinium and chlordiazepoxide for IBS and ulcers.

6. Miscellaneous Antispasmodics

• Peppermint Oil (Enteric-Coated Capsules): Used for IBS to relieve intestinal spasms naturally.
• Botulinum Toxin (Botox): Injected for focal smooth muscle spasms or dystonia.

What are some commonly prescribed antispasmodic drugs?

Antispasmodic drugs available in the U.S include:

• Dicyclomine.
• Hyoscyamine.
• Atropine.
• Scopolamine.
• Tolterodine.
• Flavoxate.
• Oxybutynin.
• Mirabegron.

Conditions Treated By Antispasmodics

• Irritable Bowel Syndrome (IBS)
• Overactive Bladder (OAB)
• Menstrual Cramps (Dysmenorrhea)
• Biliary Colic or Spasms
• Colic (intestinal or renal)
• Functional Dyspepsia