USMLE

Benztropine / Trihexyphenidyl

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Neuro Drugs
  1. Levodopa, Carbidopa
  2. Levetiracetam
  3. Valproic Acid
  4. Anticholinergic Syndrome
  5. Cholinergic Crisis
  6. Benztropine / Trihexyphenidyl
  7. Lidocaine
  8. Opioids
  9. Pyridostigmine, Neostigmine, Edrophonium
  10. Naltrexone
  11. Pregabalin
  12. Scopolamine
  13. Phenytoin
  14. Ethosuximide
  15. Succinylcholine
  16. Memantine
  17. Donepezil
  18. Halothane / Flurane
  19. Propofol
  20. Ergotamine
  21. Triptans
  22. Selegiline / Rasagiline
  23. Entacapone / Tolcapone
  24. Gabapentin
  25. Lamotrigine
  26. Carbamazepine
  27. Ramelteon

Summary

Benztropine and trihexyphenidyl are anticholinergic medications. Clinically these drugs are used to treat the symptoms of parkinson’s disease, and are also used to treat extrapyramidal symptoms or EPS, especially drug-induced parkinsonism. As anticholinergic drugs, these medications cause anticholinergic side effects like constipation, tachycardia, urinary retention, dry mouth, and so on.

Key Points

  • Benztropine (Cogentin), Trihexyphenidyl
    • Mechanism of Action
      • Anticholinergic
        • Blocks cholinergic (muscarinic) receptors, thus decreasing acetylcholine which reduces involuntary muscle movements
    • Clinical Uses
      • Tremor in Parkinson’s Disease
        • Decreases involuntary movement, tremors, and muscle rigidity
      • Extrapyramidal Side Effects
        • Side effect of antipsychotic medications
        • Pseudoparkinsonism (shuffling gait, bradykinesia, rigidity, mask-like face)
        • Dystonia (abnormal movements of face, neck and trunk)
    • Side Effects and Adverse Reactions
      • Anticholinergic effects
        •  Stops “rest and digest”
          • Dry mouth (xerostomia)
          • Decreased sweating
            • Teach patient to avoid the heat and hydrate appropriately - decreased perspiration causes the body temperature to rise and puts patient at higher risk for heat stroke
          • Constipation
            • Increase fiber and fluid intake
            • Contraindicated in patients with obstructive GI disorders, paralytic ileus, and ulcerative colitis.
          • Blurred vision, dry eyes
            • Contraindicated in closed angle glaucoma
          • Urinary retention
            • Contraindicated in benign prostate hyperplasia (BPH)
            • Carefully monitor urine output, especially in elderly patients
          • Mydriasis (dilated pupils)
          • Tachycardia
            • Palpitations
          • Dehydration
          • Dizziness, drowsiness, weakness
          • Confusion, amnesia