Chapter 23 Lecture 4

1. Chapter 23Lecture 4 Neuromuscular Disorders

2. Parkinsonism • Chronic neurologic disorder • Affects extrapyramidal motor tract - posture, balance, locomotion • Syndrome (combo. of symptoms) - bradykinesia - slow movement & tremors - rigidity - abnorm. muscle tone - No facial expression - involuntary tremors of head & neck - pill rolling movement of hands • usual onset between 50 & 70 yrs.

3. Parkinsonism • Pathophysiology: - Imbalance of neruotransmitters dopamine & acetylcholine - Degeneration of neurons originating in substantia nigra of midbrain & terminate at basal ganglia of the extrapyramidal notor tract - Cause unknown

4. Parkinsonism • 2 Neurotransmitters: • Dopamine (DA)- inhibitory - from dopaminergic neurons • Acetylcholine (ACh) - excitatory - from cholinergic neurons - Dopamine normally controls ACh & inhibits excitatory response • Degeneration of DA neurons (unknown) imbalance between DA & ACh ACh takes over excitation & stimulation of neurons releasing gamma-aminobutyric acid (GABA) movement disorders of parkinson’s • 80% of dopamine depleted by the time symptoms appear

5. ParkinsonismMedications • Drugs used to treat parkinsons are to reduce symptoms Anticholinergics - block cholinergic receptors Dopaminergics - stimulate dopamine receptors • Treats symptoms of disease - does not cure • strategy of therapy = start w/ small doses to improve symptoms able to add more drugs & doses as disease progresses

6. Parkinsonism Anticholinergics • Benztropine mesylate (Cogentin), Trihexyphenidyl (Artane), Ethopropazine (Parsidol), Orphenadrine (Norflex) - Used to decrease ACh levels - Helps w/ rigidity, sweating, drooling. tremor, depression • SE = Dry mouth & secretions, urinary retention, constipation, blurred vision

7. Parkinson’s Disease • Carbidopa/Levodopa (Sinemet) - Replaces deficient dopamine in the brain, reestablishing the dopamine/acetylcholine balance - Drug response will diminish as disease progresses - Synergistic mechanism of action

8. Parkinson DiseaseLevodopa/Carbidopa (Sinemet) • Levodopa converted to dopamine in the brain by the enzyme dopa decarboxylase • Carbidopa inhibits the enzyme dopa decarboxylase so more levodopa available to be converted to dopamine in the brain - lessens the amount of levodopa needed = lower dose • SE - N & V, dystonic movement (involuntary), nd psychotic behavior

9. Parkinson’s DiseaseDrugs • Selegiline HCL (Eldepryl) - MAO-B inhibitor - Action - unknown - may selectively inhibit MAO-B (mostly in brain) & dopamine metabolism = extends action of dopamine - Used as adjunctive therapy w/ levodopa to dec. dose - If given early, may slow progression of disease - Alert - Avoid Tyramine rich foods (cheese, red wine, bananas) may cause HTN crisis - DI - severe w/ various tricyclic antidepressants (TCA) or serotonin uptake inhibitors (SSUI)

10. Myasthenia Gravis (MG) • Autoimmune Disease • Antibody response against the acetylcholine (ACh) receptor site in skeletal muscle a degradation of ACh receptors • Lack of ACh reaching cholinergic receptors = weakness, fatigue of skeletal muscles & weak resp. muscles • Drugs for controlling MG = AChE inhibitors or cholinesterase inhibitors & anticholinesterase that inhibit action of the enzyme more ACh activates cholinergic receptors & promotes muscle contraction (parasympathomimetics)

11. Myasthenia GravisMedications • Neostigmine (Prostigmin), Pyridostigmine bromide (Mestinon), Ambenonium (Mytelase) - Used to control MG - diff. lengths of action - must be given on time to prevent muscle weakness - Cholinergic crisis can result w/ overdosing (extreme weakness, inc. salivation, tears, sweating) - atropine sulfate should be available to counteract the OD • Edrophonium chloride (Tensilon) - used in diagnosing MG - ptosis (droopy eyelid) gone in 1 - 5 min. & to distinguish between MG & cholinergic crisis

12. Chapter 15Central Nervous System (CNS) • Brain & Spinal Cord - regulates body functions • Receives signals from sensory receptors - pain, cold, smell - by way of afferent nerves • Info. is processed & controls body response w/ signals sent via efferent nerves for cellular action • Stimulation of the CNS may either increase nerve cell (neuron) activity, or block nerve cell activity

13. CNS • Blood Brain Barrier - BBB - Impedes entry of drugs into the brain d/t the cells composing the walls of the capillaries surrounding the brain being tight 1. lipid soluble agents can cross - Chloromycetin 2. Drugs w/ specific “transport systems” can cross - Claforan, Rocephin, Mefoxin (+) - Protects the brain from invasion of potentially toxic substances (-) - Significant obstical in treatment of CNS infections

14. CNS • CNS neurotransmitters - Unlike PNS - There are a lot of them - Exact functional role not clear - Complexity makes it difficult to know exactly how CNS drugs work • CNS has ability to alter effects of drugs when taken chronically. Adaptive changes occur in brain w/ prolonged use Can produce alterations in theraputic & side effects • Tolerance & physical dependence can occur Tolerance = dec. response with prolonged use (Parkinson’s) Dependence = Abrupt withdrawl = withdrawl syndrome (illegals)

15. CNS Stimulants • Major stimulants = - Amphetamines & caffeine - stimulate cerebral cortex of brain - analeptics & caffeine - act on brain stem & medulla to stimulate respirations - anorexiants - act on cerebral cortex & hypothalamus to suppress appetite • Uses - narcolepsy, attention deficit disorder (ADD), appetite suppressants, stimulate respirations, & migraine headaches

16. Chapter 16 Central Nervous System Depressants: Sedative-Hypnotics

17. Sedative - Hypnotics • Problem State - Insomnia • Adequate sleep important for maintainance of body functions. 4 stages: 1. I & II = light sleep - easy arousal 2. III = transition from light to deeper 3. IV = Deep sleep - dreamless, restful Bp & resp 4. Rapid Eye Movement (REM) - Dreaming phase. Reestablishes psyhic equilibrium

18. Sedative - Hypnotics • Insomnia = Most common sleep disorder - Symptom of physical or emotional distress • Desired Drug Action = calm client, little or no daytime sedation or drowsiness, fall asleep quickly, awaken refreshed without any drug hangover • Problem caused by - difficulty falling asleep, staying asleep, early morning awakenings • One of the most frequently prescribed drugs d/t high incidence of sleep disorders

19. Sedative/Hypnotics • Drugs used in conjunction with altered patterns of sleep: - Hypnotic - drug that produces “natural sleep” - Sedative - diminishes physical & mental responses, but doesn’t affect consciosness. Quiets the client. Used mostly during the daytime. - dose of drug may induce sleep • Sedative/hypnotics are sometimes the same drug, but certain drugs used more often for hypnotic effect

20. Sedative/HypnoticsBarbiturates • Not as commonly used for sleep/sedation d/t side effects & potential for abuse - benzodiazepines more frequently used today • Long, intermediate, short & ultrashort - acting • Elderly should not take - CNS depression • Restict use (2 weeks or less) d/t side effects & drug tolerance • Class II

21. Sedative/HypnoticsBarbiturates • Pentobarbital (Nembutal) - short-acting, long t1/2 * rapid onset, short duration of action * Primarily used to induce sleep & for sedation needs * many drug interactions Alert - Don’t confuse with Phenobarbital • Phenobarbital - long acting * Used to control seizures in epilepsy * Used for pre-op sedation

22. Sedatives/HypnoticsBenzodiazepines • Considered safer than barbiturates - short-acting • Closer to ideal/desired action • Effective for sleep disorders for several weeks longer than other sedative-hypnotics • Should not be used for longer than 3 - 4 weeks as a hypnotic to prevent REM rebound • Small doses may be used for clients with renal or hepatic dysfuction

23. Sedative/HypnoticsBenzodiazepines • Flurazepam (Dalmane) - intermediate to long acting, long t1/2, highly protein bound * Used to treat insomnia by inducing & sustaining sleep * Rapid onset of action • Triazolam (Halcion) - short-acting hypnotic * Used to treat insomnia * May cause memory loss with prolonged use • Temazepam (Restoril) - hypnotic * Used for insomnia & to dec. nocturnal awakenings