You can find part 1 here –
http://www.nclexreviewonline.com/nervous-system-medication-part-1-the-receptors/
CI means Contra Indicated
Medications Affecting the Nervous System
(General Points)
- Adaptive changes within brain with prolonged exposure
- increased therapeutic effect
- decreased side effects
- Tolerance, physical dependence
- Do not stop abruptly
- Highly variable individual response to mediations
Parkinson’s Disease
- Treatment uses two main classes:
- Meds that activate dopamine receptors (directly or indirectly)
- Meds that block acetylcholine receptors
Seizure Disorders
- different types of seizures respond to different medications
- Usually require life-long management
- Meds must be discontinued slowly over 6 weeks to several months
Schizophrenia
- Clinical course includes semi-remission punctuated by acute exacerbations
- Positive symptoms (Agitation, delusions)
- Conventional antipsychotic -> Thorazine
- Atypical antipsychotic -> Clozapine
- Negative symptoms (Social withdrawal, poor self-care)
- Atypical antipsychotic -> Clozapine
- Cognitive symptoms (Difficulties with memory and learning)
- Initial doses are high and given throughout day; maintenance doses given at bedtime.
Depression
- Symptom relief can take 1-3 weeks and possibly 2-3 months
- Three main groups:
- Tricyclic antidepressants (TCAs)
- Selective serotonin reuptake inhibitors (SSRIs)
- Monamine oxidase inhibitors (MAOIs)
Bipolar Disorder
- Typically managed with mood stabilizers. Antipsychotics and antidepressants may be used during acute episodes of mania or depression.
- Lithium
- Valproic acid (Depakote)
- Carbamazepine (Tegretol)
Cholinesterase Inhibitors
Expected Action:
Prevents ACh degradation -> increase transmission of nerve impulses by increasing [ACh]
Examples: Neostigmine, Physostigmine
Therapeutic Uses:
- Increases muscle strength by increasing [ACh] at neuromuscular junction in myasthenia gravis
- Reversal of nondepolarizing neuromuscular blocking agents (tubocurarine)
Adverse Effects:
- Excessive muscarinic stimulation: increase GI motility & secretions, bradycardia, urinary urgency (side effect can be treated with atropine)
Cholinergic crisis: Above plus resp. depression from neuromuscular blockade.
Adverse Effects:
Pregnancy (C)
CI in obstruction of GI/GU systems / caution with seizures, asthma, bradycardia, hypotension, peptic ulcer disease
Interactions:
Tubocurarine – Neostigmine reverses blockade
Atropine – counteracts
Succinylcholine – increase neuromuscular blockade
Education
Wear medic-alert bracelet
Neuromuscular Blocking Agents
Expected Action:
Block ACh at neuromuscular junction – don’t cross blood-brain barrier
Examples: Nondepolarizing: tubocurarine, pancuronium Depolarizing: succinylcholine
Therapeutic Uses:
Adjuncts to general anesthesia
Control spontaneous respiration in ventilated pts.
Diagnose myasthenia gravis
Succinylcholine for: electroconvulsive therapy, intubation, endoscopy
Adverse Effects:
Hypotension from histamine release & ganglionic blockade
Bradycardia, dysrhythmias
Respiratory arrest
Succinylcholine: Low pseudocholinesterase activity -> apnea
Malignant hyperthermia (dantrolene)
Pain
Hyperkalemia
Contraindications/Precautions:
Pregnancy (C)
SCh: CI for hyperkalemia (trauma, burns)
Interactions:
General anesthetics
Aminoglycosides/tetracyclines – increase NM blockade
Neostigmine/ChE inhibitors: decrease η nondepolarizing / increase η depolarizing
Dopaminergics
(Anti-Parkinson’s)
Expected Action:
Levodopa taken up and converted to dopamine. Carbidopa augments levodopa by preventing conversion to dopamine in intestine and periphery (increase [DA] in CNS).
Examples: Levodopa, carbidopa, Sinemet
Therapeutic Uses: Symptomatic relief from dyskinesias
Adverse Effects:
Dyskinesias
Discoloration of sweat & urine
Nausea / drowsiness
Orthostatic hypotension
Psychosis (clozapine)
Activation of malignant melanoma
Contraindications/Precautions:
!! with cardiac or psychiatric disorders
CI with melanoma
2 weeks from MAOI
Pregnancy (C)
Interactions:
Proteins interfere with absorption and transport
- Conventional antipsychotics (haldol, compazine) decreaseη
Pyridoxine decrease η
MAOI hypertension
Carbidopa, dopamine agonists, anticholinergics, COMT inhibitors and dopamine releasers ñ therapeutic effects
COMT
- Catechol O-Methyltransferase
- Deactivates catecholamines (dopamine, norepinephrine, acetylcholine, epinephrine, serotonin, histamine, etc)
- Found in post-synaptic cell membranes of adrenergic neurons where it degrades norepinephrine.
- Also found in gut
Dopamine Agonists
(Anti-Parkinson’s)
Expected Action:
Act directly on dopamine receptors
Examples: Pramipexole, ropinirole, bromocryptine
Therapeutic Uses: Monotherapy early / combined with levodopa in later stages
Adverse Effects:
- Sleep attacks (nightmares)
- Orthostatic hypotension
- Daytime sleepiness
- Psychosis
- Dyskinesias
- Nausea
Contraindications/Precautions:
Pregnancy (C)
Caution with liver & kidney impairment
Interactions:
- Levodopa: Can decrease motor-control fluctuations permitting lower dose
Levodopa: Also increase risk of orthostatic hypotension and dyskinesias
Centrally Acting Anticholinergics
(Anti-Parkinson’s)
Expected Action:
Block ACh at muscarinic receptors which helps maintain ACh, dopamine balance
Examples Benztropine (Cogentin), trihexyphenidyl (Artane)
Adverse Effects:
Nausea (take ĉ food)
Atropine-like effects (dry mouth, blurred vision, mydriasis, constipation)
Antihistamine effects (sedation, drowsiness)
Contraindications/Precautions:
CI in narrow-angle glaucoma
Antiviral
(Anti-Parkinson’s)
Expected Action:
Stimulate dopamine release, prevent dopamine reuptake, and may block cholinergic and glutamate receptors
Examples: Amantadine
Therapeutic Uses: Parkinson’s Disease
Adverse Effects: CNS Effects, Discoloration of skin (temporary), Atropine-like effects
Next week we’ll continue.
