Antispasmodics (Spasmolytic)

• Drug that suppresses muscle spasms (relaxes muscles)
• Used for smooth muscle contraction, especially in tubular organs of the gastrointestinal tract (and genitourinary tract)
• Spasm also seen in movement disorders featuring spasticity in neurologic conditions- Cerebral Palsy, Multiple Sclerosis and Spinal Cord disease

Classification of Antispasmodics:

ANTICHOLINERGIC/ANTIMUSCARINIC AGENTS

Dicyclomine Hydrochloride	Hyoscine butyl bromide	Atropine methonitrate
Hyoscyamine Sulfate	Pipenzolate methyl bromide	Valethamate
Cimetropium Bromide	Otilanium Bromide	Clidinium
Prifinium Bromide	Solifenacin	Darifenacin
Oxybutynin	Tolterodine	Flavoxate

SMOOTH MUSCLE RELAXANTS

Mebeverine Drotaverine

Papaverine-like agents Organic nitrates

Alverine Calcium channel blocker (Pinaverium Bromide)

OTHERS

• Low dose Amitriptyline (10-25 mg at night) in patients who do not respond to antispasmodics Bamboo shoots
• Peppermint oil
• Relaxation therapy, hypnotherapy and cognitive behaviour therapy have a place in selected cases

Why not Opioids?

• These drugs themselves cause spasm of visceral smooth muscle and have a simultaneous action tending to increase the pain
• An antimuscarinic drug such as atropine or Hyoscine may be given simultaneously to antagonize this effect
• Atropine is less effective in biliary colic, not able to completely counteract biliary spasm due to opiates (nitrates are more effective)

MOA OF ANTICHOLINERGIC AGENT

• Parasympathetic nerves enhance both tone and motility
• Reduced the tone and amplitude of contractions of stomach and intestine – the passage of chyme is slowed—spasm relieved (Constipation may occur)

• Atropine completely abolish the effects of ACh (and other parasympathomimetic drugs) on GI motility and secretion
• Inhibits incompletely the gastrointestinal responses to vagal stimulation
• Relatively large doses needed to produce such inhibition
• Enteric nervous system regulate motility independently of parasympathetic control
• Parasympathetic nerves serve only to modulate the effects of the enteric nervous system

HYOSCINE BUTYL BROMIDE

• 20–40 mg oral, i.m., s.c., i.v.; (10 mg tab., 20 mg/ml amp.)

ATROPINE METHONITRATE

• 2.5–10 mg oral, i.m
• For abdominal colics and hyperacidity

CLIDINIUM

• 2.5–5 mg oral
• Antisecretory antispasmodic used in combination with benzodiazepines for nervous dyspepsia, gastritis, irritable bowel syndrome, colic, peptic ulcer

PIPENZOLATE METHYL BROMIDE

• 5–10 mg (children 2–3 mg) oral
• Promoted especially for flatulent dyspepsia, infantile colics and abdominal cramps

Dicyclomine

• 20 mg oral/i.m., children 5–10 mg
• Direct smooth muscle relaxant action in addition to weak anticholinergic
• Exerts antispasmodic action at doses which produce few atropinic side effects
• Infants have exhibited atropinic toxicity symptoms and not recommended below 6 months of age

Mebeverine

• • Reserpine derivative
  • Muscolotropic spasmolytic with a strong and selective action on the smooth muscle spasm of the gastrointestinal tract, particularly of the colon
  • Direct effect on colonic muscle activity, especially, it appears, on colonic hypermotility
  • Does not possess antimuscarinic activity
  • Does not exhibit the troublesome unwanted effects of that group of drugs

Papaverine

• • Opium alkaloid used to treat visceral spasms
  • Experimental importance

Drotaverine

• • Novel non-anticholinergic smooth muscle antispasmodic
  • Acts by inhibiting phosphodiesterase-4 (PDE-4) selective for smooth muscle
  • Elevation of intracellular cAMP/cGMP attends smooth muscle relaxation
  • Used orally as well as parenterally in intestinal, biliary and renal colics, irritable bowel syndrome, uterine spasms, etc. without anticholinergic side effects

Adverse effects:

 Headache, dizziness, constipation and flushing

 Fall in BP on i.v. injection

• • Dose: 40–80 mg TDS, 40 mg/2 ml inj