Pridinol Mesilate

A. Approved Indications

• Skeletal Muscle Spasms of various origins:
• Acute and chronic painful muscle spasms
• Muscle spasms due to orthopedic injuries or surgical procedures
• Lumbago, sciatica, cervical syndrome
• Intervertebral disc disorders
• Tension neck syndrome
• Acute torticollis (wry neck)
• Spasticity of Central Origin (as adjunctive treatment):
• Stroke-related spasticity
• Spasticity in cerebral palsy or brain/spinal cord injury
• Supportive Therapy in musculoskeletal rehabilitation

B. Clinically Accepted Off-Label Uses

• Temporomandibular Joint Disorder (TMJ) with muscular spasm
• Myofascial Pain Syndromes
• Muscle contractures following neuromuscular dysfunction

Route of Administration:

• Oral tablets (primary use)
• Intramuscular (IM) or intravenous (IV) injections (for acute settings)

Adults:

• Oral:
  4 mg to 6 mg three times daily (max: 24 mg/day)
  Dose may be adjusted depending on severity and patient response.
• IM/IV Injection:
  4 mg once or twice daily as needed in acute spasm
  Only for short-term use under medical supervision

Elderly:

• Start with the lowest effective dose (e.g., 4 mg twice daily)
• Monitor for CNS effects and anticholinergic burden

Pediatrics:

• Not recommended due to insufficient safety and efficacy data

Renal or Hepatic Impairment:

• Use with caution
• No specific dosage guidelines available; monitor closely for side effects

Duration:

• Use should be limited to short-term therapy (7–14 days)
• Long-term use only if clearly indicated and monitored

Pridinol mesilate is a centrally acting anticholinergic muscle relaxant that exerts its effect primarily by inhibiting polysynaptic reflexes in the spinal cord and subcortical brain regions. It acts as a non-selective muscarinic receptor antagonist, which reduces excitatory cholinergic transmission, leading to decreased muscle tone and suppression of involuntary muscle contractions. This action results in symptomatic relief of painful spasms and improved range of motion in affected muscles without acting directly on skeletal muscle fibers.

• Absorption:
  Rapid oral absorption; peak plasma levels reached within 1–2 hours
• Bioavailability:
  Moderate; affected by hepatic first-pass metabolism
• Distribution:
  Distributed throughout body tissues; crosses blood-brain barrier
• Metabolism:
  Extensively metabolized in the liver to inactive compounds
• Elimination Half-life:
  Approximately 3 to 5 hours
• Excretion:
  Primarily through the urine as metabolites
  Minimal amounts of unchanged drug excreted

• Pregnancy:
  Not assigned a specific FDA category
  Animal studies are insufficient; human data are lacking.
  Use only if potential benefits justify potential risks. Avoid during the first trimester.
• Lactation:
  Unknown whether pridinol is excreted in breast milk.
  Avoid use while breastfeeding or use with caution and monitor infant for sedation, dry mouth, or feeding issues.

• Class: Centrally Acting Skeletal Muscle Relaxant
• Subclass: Anticholinergic Piperidine Derivative

• Hypersensitivity to pridinol or any excipients
• Narrow-angle glaucoma
• Myasthenia gravis
• Prostatic hypertrophy or urinary retention
• Tachyarrhythmias or severe cardiac disease
• Severe hepatic impairment

• Anticholinergic effects:
  Dry mouth, blurred vision, constipation, and urinary retention are common
  Use cautiously in patients with glaucoma, BPH, or elderly patients
• CNS depression:
  May cause sedation, dizziness, and confusion—avoid driving or operating heavy machinery
• Neuropsychiatric effects:
  Rarely causes hallucinations or agitation at high doses, particularly in the elderly
• QT Prolongation Risk:
  Caution in patients with known prolonged QT or electrolyte imbalance
• Use in combination:
  Use cautiously with other CNS depressants or anticholinergics due to additive effects

Common (≥1%):

• CNS: Drowsiness, dizziness, fatigue
• Gastrointestinal: Dry mouth, nausea, constipation
• Ocular: Blurred vision, accommodation disorders
• Genitourinary: Difficulty in urination, especially in males

Less Common/Serious:

• Cardiac: Palpitations, tachycardia
• Neuropsychiatric: Confusion, restlessness, hallucinations
• Allergic reactions: Rash, itching, facial swelling (rare)

Side effects are more likely at higher doses and in sensitive populations (e.g., elderly).

• CNS Depressants (e.g., opioids, benzodiazepines, alcohol):
  Enhanced sedative and respiratory depressant effects
• Other Anticholinergics (e.g., antihistamines, tricyclic antidepressants):
  Increased risk of dry mouth, blurred vision, constipation, and urinary retention
• MAO Inhibitors:
  Increased risk of central adverse effects—concurrent use not recommended
• Antihypertensives:
  May enhance hypotensive effect, especially with IV administration
• Enzyme Interaction:
  Metabolized hepatically; no major interaction with CYP450 enzymes identified

• Pharmacovigilance updates:
  Emphasize cautious use in elderly due to CNS and anticholinergic effects
• Therapeutic guidelines in some countries now limit use to 7–14 days for acute episodes only
• Warnings reinforced regarding QT prolongation and psychiatric effects in predisposed individuals

• Oral Tablets:
  Store at 20°C to 25°C (68°F to 77°F)
  Protect from moisture and direct light
  Keep in original container; tightly closed
• Parenteral Form (if applicable):
  Store protected from light
  Do not freeze
• General:
  Keep out of reach of children
  Discard after expiration date as per manufacturer guidelines