Introduction to Central Nervous System Pharmacology

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Introduction to Central Nervous System
Pharmacology
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Intro. to Central Nervous System Pharmacology

• Central nervous system agents act on the brain
  and spinal cord
• Transmitters of the central nervous system are
• Acetlcholine
• Norepinephrine
• Epinephrine

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Chemical Imbalances

• Norepinephrine
• Dopamine
• Acetylcholine
• Serotonin
• Gamma amino butyric acid (GABA)
• Glutamate

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Central Nervous System Drugs

• The brains ability to adapt to a drug can
  produce alterations in therapeutic effects and in
  side effects.

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Drugs for Parkinsons Disease

• Central Nervous System

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Drugs for Parkinsons Disease

• Parkinsons disease is a disorder of the
  extrapyramidal system associated with disruption
  of neurotransmissions within the striatum
• Dyskinesias (Disorder of movement)
• Dopamine and acetylcholine

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Parkinsons Disease

• Dyskinesias of Parkinsons disease are
• Tremor at rest
• Rigidity
• Postural instability
• Bradykinesia (slow movement)
• Akinesia (complete absence of movement)

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Parkinsons Disease (cont.)

• Therapeutic goal
• Improve ADLs
• Drug selection and dosages are determined by
  activities of daily living performance

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Classification of Drug Therapy for Parkinsons
Disease

• Two major categories
• Dopaminergic agents
• Promote activation of dopamine receptors
• Levodopa (Dopar)
• Anticholinergic agents
• Prevent activation of cholinergic receptors
• Benztropine (Cogentin)

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Dopaminergic Agents

• Mechanism of Action
• Promotion of dopamine synthesis
• Prevention of dopamine degradation
• Promotion of dopamine release
• Direct activation of dopamine receptors

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Anticholinergic Agents

• Mechanism of action
• Blockade of muscarinic cholinergic receptors in
  the striatum

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Drug Therapy for Parkinsons Disease

• Levodopa
• Carbidopa
• Amantadine
• Bromocritine
• Pergolide
• Selegiline
• Benztropine

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Drugs for Epilepsy

• CNS Pharmacology

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Drugs for Epilepsy

• Group of disorders characterized by excessive
  neuron stimulation within the central nervous
  system

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Seizure Types

• Partial (focal)Seizures
• Simple partial
• Complex partial
• Generalized seizures
• Convulsive (tonic-clonic)/Grand Mal
• Nonconvulsive (absence)/Petite Mal

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Antiepilectic Drugs

• Suppress neuronal discharge at the seizures
  focus and brain
• Mechanism of action
• Suppression of sodium influx
• Suppression of calcium influx

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Epilepsy- Therapeutic Considerations

• Treatment goal
• Diagnosis
• Drug Selection
• Plasma drug levels
• Compliance
• Withdrawal

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Phenytoin

• Partial and tonic-clonic seizures
• Mechanism of action-selective inhibition of
  sodium channels
• Varied oral absorption
• Half-life 8-60 hours

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Phenytoin (cont.)

• Adverse effects
• Nystagmus
• Sedation
• Ataxia
• Diplopia
• Cognitive Impairment

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Phenytoin (cont.)

• Drug interactions
• Decreases effect of oral contraceptives,
  warfarin, glucocorticoids
• Increases levels of diazepam,isoniazid,cimetidine,
  alcohol, valporic acid

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Phenobarbital

• Uses
• Partial and generalized tonic-clonic seizures
• Promotes sleep and sedation
• Adverse Effects
• Physical dependence/porphyria
• Nystagmus/Ataxia
• CNS Depression

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Carbamazepine (Tegretol)

• Uses
• Partial and tonic-clonic seizures
• Bipolar disorders
• Trigeminal Neuralgias
• Adverse Effects
• CNS symptoms-nystagmus, ataxia
• Anemia,leukopenia, thrombocytopenia

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Valproic Acid (Depakene)

• Uses
• Absence seizures
• Other seizures
• Migraine
• Adverse Effects
• Hepatoxicity
• Teratogenic effects

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Drugs for Headaches

• CNS Pharmacology

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Drugs for Headache

• Migraine Headaches
• Inflammation and dilation of intracranial blood
  vessels
• Head Pain
• Types
• With aura (classic migraine)
• Without aura (common migraine)

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Drug Therapy for Migraine Headache

• Objective
• To abort ongoing attack
• To eliminate headache pain
• Suppress nausea and vomiting
• To prevent attacks
• Prophylaxis

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Drug Therapy for Migraine Headache (cont.)

• Drugs to abort an attack
• Aspirin-like analgesics (Motrin)
• Opioid analgesics (Demerol)
• Ergot alkaloids (Ergomar)
• Serotonin agonists (Sumatriptan)

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Drug Therapy for Migraine Headache (cont.)

• Drugs for prophylaxis
• Beta blockers (atenolol)
• Calcium channel blockers (verapimil)
• Tricyclic antidepressant (amitryptyline)
• Methysergide (sansert)
• Sodium divalproex (depakote)

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Opioid (Narcotics) Analgesics

• CNS Pharmacology

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Opioid (Narcotic) Analgesics

• Analgesic
• Relieves pain without loss of consciousness
• Opiod
• Drug similar to morphine
• Derived from opium

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Opioid Receptors

• Mu- Pure opioid agonists
• Kappa
• Delta

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Morphine

• Used for relief of moderate and severe pain
• Decreases sensation of pain
• Decreases the emotional reaction to pain

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Morphine

• Adverse Effects
• Respiratory depression
• Constipation
• Orthostatic hypotension
• Urinary Retention
• Cough suppression
• Emesis

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Tolerance

• Tolerance
• Increasing doses to obtain same response
• Develops with analgesia, euphoria, sedation,
  respiratory depression
• Cross-tolerance to other opioid agonists

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Physical Dependence

• Abstinence syndrome occurs if drug abruptly
  stopped
• Abstinence syndrome is dependent on
• Half life of drug
• Degree of physical dependence

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Opioid Overdose

• Classic Triad
• Coma
• Respiratory depression
• Pinpoint pupils
• Treatment
• Ventilatory support
• Opioid antagonist

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Non-drug Therapy for Pain Management

• Application of heat and cold
• Massage
• Exercise
• Acupuncture
• Relaxation
• Imagery
• Peer group support

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Pain Management in Patients with CA

• CNS Pharmacology

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Pain Management

• Pain
• Unpleasant sensory and emotional experience
  associated with tissue damage
• Patients pain description is the cornerstone of
  pain assessment

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Types of Pain

• Nociceptive pain
• Results from injury to tissues
• Called somatic or visceral pain
• Neuropathic pain
• Results from injury to peripheral nerves
• Responds poorly to opiods

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Clinical Approach to Pain Management

• A- Ask and assess
• B- Believe
• C- Choose
• D- Deliver
• E- Empower and enable

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Pain Assessment

• Assessment parameters of pain
• Onset and temporal patterns
• Location
• Quality
• Intensity
• Modulating Factors
• Previous treatment
• Impact

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WHO Analgesic Ladder

• Step 1- Mild to moderate pain
• Nonopiod analgesic
• Step 2- More severe pain
• Add opioid analgesic
• Step 3- Severe pain
• Substitute opioid-morphine