Drugs used in Parkinsonism

Benzodiazepines
Benzodiazepines are well absorbed when given orally. They bind strongly to plasma proteins,
however, many of them accumulate gradually in the body fat (i.e. they are highly lipid soluble).
Benzodiazepines are inactivated by the liver and excreted in the urine.
Based on their duration of action roughly divided into short acting (flurazepam, triazolam),
medium acting (alprazepam, lorazepam) and long acting compounds (diazepam,
chlordiazepoxide, clonazepam).
Pharmacodynamics
Act by binding to a specific regulatory site on the GABAA receptor, thus enhancing the inhibitory
effects of GABA. Central nervous system effects of benzodiazepines include:

1. Reduction of anxiety and aggression.
2. Sedation and induction of sleep.
3. Reduction of muscle tone and coordination.
4. Anticonvulsant effects.
   Clinical Uses

• Treatment insomnia
• Anxiety
• Preoperative mediations
• Acute alcohol withdrawal
• As anticonvulsants
• Chronic muscle spasm and spasticity
  Unwanted effects
• Toxic effects due to acute overdosage causes prolonged sleep.
• Unwanted effects occurring during normal therapeutic use includes: drowsiness,
  confusion, amnesia, and impaired motor coordination.
• Tolerance and dependance: Pharmacokinetic and tissue tolerance and also cause
  physical dependance. i.e. stopping benzodiazepines treatment after weeks or months
  causes an increase in symptoms of anxiety.
  
  5 – HT1A receptor agonist
  Buspirone is a potent agonist of. 5 – HT1A receptors. Anxiolytic effects take days to weeks to
  develop. Buspirone does not cause sedation, motor incoordiation and withdrawal effects. The
  main side effects are nausea, dizziness, headache, and restlessness.
  Barbiturates
  They are non-selective CNS depressants, which produce effects ranging from sedation and
  reduction of anxiety, to unconsciousness and death from respiratory and cardiovascular failure.
  Barbiturates act by enhancing action of GABA, but less specific than benzodiazepines. They are
  potent inducers of hepatic drug metabolizing enzymes, hence likely to cause drug interaction.
  Tolerance and dependance occur, more than benzodiazepines.