© Paradigm Publishing, Inc. 1 Chapter 8 Drugs for Central Nervous System Disorders
Dec 25, 2015
© Paradigm Publishing, Inc. 1
Chapter 8
Drugs for Central Nervous System
Disorders
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Learning Objectives
• Develop an understanding of the physiologic processes that occur in epilepsy.
• Classify seizures and the goals of their therapy.
• Understand that specific drugs are used in different classes of seizures.
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Learning Objectives
• Be familiar with Parkinson disease and the drugs used in its treatment.
• Identify the drugs and goals of therapy for attention-deficit disorders.
• Realize that some drugs may be used for several disease states.
• Recognize drugs used to treat Alzheimer disease.
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Epilepsy
• Common neurologic disorder with sudden and recurring (paroxysmal) seizures
• Caused by abnormal electrical impulses in the brain
• All epilepsy patients have seizures; not all with seizures have epilepsy
• 1% to 2% have chronic epilepsy
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Seizures
• Disturbances of neuronal electrical activity that interferes with normal brain function
• Behavior change patient not aware of
• Conscious periods may or may not lose control over movement
• Loss of body control may affect one area or entire body
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Convulsions
• Excessive firing of neurons can result in a convulsion– Involuntary contraction or series of
contractions of the voluntary muscles
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Causes of Seizures
• Imbalance of excitatory and inhibitory neurotransmitters– GABA: excitatory– Glutamate: inhibitory– Other neurotransmitters can be involved
• Enzymes control neurotransmitter levels• Disruption in enzymes = disruption of
neurotransmitters
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Causes of Seizures
• Alcohol or drug withdrawal• Epilepsy• High fever• Hypoglycemia, hyperglycemia• Infection (meningitis)• Neoplasm (brain tumor)• Trauma or injury (head, hematoma)
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Two Classes of Seizures
• Partial– Simple partial– Complex partial
• Generalized– Tonic-clonic (was called grand mal seizure)– Absence (was called petit mal seizure)– Myoclonic– Atonic
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Partial Seizures
• Localized in a specific area of the brain• Almost always results from injury to
cerebral cortex• Occurs in about 65% of people with
epilepsy• Can progress to generalized seizures
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Two Classes of Partial Seizures
• Simple Partial– No loss of consciousness– May have muscle twitching or sensory
hallucinations
• Complex Partial– Impaired consciousness– Confusion, blank stare, and postseizure
amnesia
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Generalized Seizures
• Involves both hemispheres of the brain, no specific location
• Four types
• Tonic-Clonic– Absence– Myoclonic– Atonic
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Tonic-Clonic Seizures
• Tonic: body becomes rigid, patient may fall, lasts a minute or less
• Clonic: starts with muscle jerks, may be accompanied by shallow breathing, loss of bladder control, and excess salivation– Lasts a few minutes
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Absence Seizures
• Interruption of activities by blank stare, rotating eyes, uncontrolled facial movements, rapid eye blinking, twitching or jerking of an arm or leg
• No generalized convulsions• Usually lasts 30 seconds or less• Most prevalent first 10 years of life. 50% of
children have tonic-clonic as grow older
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Myoclonic Seizures
• Occurs with sudden, massive, brief muscle jerks which may throw patient down or nonmassive, quick jerks
• Consciousness is not lost
• Can occur during sleep
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Atonic Seizures
• Begins with sudden loss of muscle tone and consciousness
• Patient may collapse, head drop, arm or leg may go limp
• Lasts few seconds to a minute, then patient can stand and walk again
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Status Epilepticus
• Continuous tonic-clonic seizures, with or without return to consciousness
• Last at least 30 minutes
• High fever and lack of oxygen that can cause brain damage or death
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Two Goals of Antiepileptic Therapy
• Seizure control or lessen the frequency
• Prevent emotional and behavioral changes that may result from seizures
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Antiepileptic Drug Therapy
• Different seizure types require different drugs
• Start with monotherapy at low dose and increase slowly over 3 to 4 weeks
• Medication must be maintained at steady therapeutic levels
• If insufficient response, polytherapy can be considered
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Antiepileptic Drug Therapy
• Newer drugs are seizure-specific• High potential for drug interactions• Anticonvulsants have narrow therapeutic
ranges• Minor dosage changes can result in loss of
seizure control or toxicity• Prescribers often write for the brand name
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Drug ListAnticonvulsants
– carbamazepine (Epitol, Tegretol)
– clonazepam (Klonopin)
– diazepam (Valium)
– divalproex (Depakote)
– ethosuximide (Zarontin)
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Drug ListAnticonvulsants
– fosphyenytoin (Cerebyx)
– gabapentin (Neurontin)
– lamotrigine (Lamictal)
– levetiracetam (Keppra)
– lorazepam (Ativan)
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Drug ListAnticonvulsants
– oxcarbazepine (Trileptal)
– phenobarbital (Luminal Sodium)
– phenytoin (Dilantin)
– pregabalin (Lyrica)
– primidone (Mysoline)
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Drug ListAnticonvulsants
– tiagabine (Gabitrol)
– topiramate (Topamax)
– valproic acid (Depakene)
– zonisamide (Zonegran)
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Dispensing Issues of Anticonvulsants
• Prescribers often do not allow generic drugs
• Pharmacy technicians watch for DAW
• If computer changes drug to generic, technicians often change drug to brand
Warning!
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carbamazepine (Epitol, Tegretol)
• Effect on sodium channels which may alter synaptic transmission
• Blood monitoring important
• Many interactions with other drugs
• Side effects can be serious
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clonazepam (Klonopin)
• Prophylaxis of seizures
• Depresses nerve transmission in the motor cortex
• C-IV controlled substance (benzodiazepine)
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gabapentin (Neurontin)
• Used as adjunct
• No significant drug interactions, well-tolerated, easy to use
• Used for many other disorders, particularly neuropathic pain
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Dispensing Issues of Neurontin
• Sound-alike drugs, but different strengths– Neurontin, usually 100 mg– Noroxin (antibiotic), usually 400 mg
Warning!
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lamotrigine (Lamictal)
• Add-on therapy for adults with partial seizures
• Blocks sodium channels which reduces neuron excitation
• Call physician immediately if rash appears, do not discontinue abruptly
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Dispensing Issues of Lamictal
• Look-alike and sound-alike– Lamictal– Lamisil (terbinafine), antifungal– Lomotil (diphenoxylate-atropine),
diarrhea
Warning!
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Dispensing Issues of Lamictal
• Black Box warning about fatal rashes, most serious warning
• Boxed warnings are special warnings about a drug highlighted in the FDA-approved product information
Warning!
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phenytoin (Dilantin)
• May be used to prevent seizures• Promotes sodium outflow from cells,
stabilizing the neuronal membrane• Be cautious of drug interactions• IV phenytoin must be mixed carefully
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Side Effects of Phenytoin: Dose Related
• Ataxia
• Diplopia
• Dizziness
• Drowsiness
• Encephalopathy
• Involuntary movements
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Side Effects of Phenytoin: Non-Dose-Related
• Gingival hyperplasia
• Peripheral neuropathy (pain in extremities
• Vitamin deficiencies
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pregabalin (Lyrica)
• Reduces release of neurotransmitters glutamate, norepinephrine, substance P
• Similar to gabapentin, more potent. Fewer side effects than other anticonvulsants
• Controlled substance, Schedule V
• Also approved to treat diabetic neuropathy
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taigabine (Gabitrol)
• Blocks reabsorption of GABA, allowing it to bind to nerve cells which enhances normal brain activity
• Should be taken with food• Can cause seizures if patients who do not
have epilepsy use it off-label
• FDA has issued off-label use warning
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topiramate (Topamax)
• Thought to block sodium channels which increases GABA activity and decreases glutamine activity
• Causes significant cognitive effects
• Drink fluids to decrease risk of kidney stones
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Discussion
Which neurotransmitters play the greatest role in seizures?
The neurotransmitters are glutamate (excitatory) and GABA (inhibitory).
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Terms to Remember
epilepsy
seizure
convulsion
partial seizure
generalized seizure
tonic-clonic seizure
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Terms to Remember
grand mal seizure
absence seizure
petit mal seizure
myoclonic seizure
atonic seizure
status epilepticus
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Terms to Remember
anticonvulsant
adjunct
ataxia
substance P
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Parkinson Disease
• Characterized by tremor when resting, rigidity, and akinesia (absence of movement)
• Poor posture control, shuffling gait, loss of overall muscle control
• Usually affects people over 60
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Physiology of Parkinson Disease
• Parkinson disease is result of alterations in the extrapyramidal system– Part of the CNS that controls motor activities
– Made up of the basal nuclei (basal ganglia)
• Most common extrapyramidal disease
• Parkinson has no definitive test, diagnosed by symptoms
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Cutaway View of the Brain
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Physiology of Parkinson Disease
• For normal muscle movement to be performed, 2 main neurotransmitters must be in balance– Dopamine (inhibitor)
– Acetylcholine (stimulator)
• In Parkinson disease, these neurotransmitters are not in balance
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Dopamine and Parkinson Disease
• In the substania nigra, insufficient dopamine is released to counteract effects of Ach
• This causes excessive motor nerve stimulation
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Substantia Nigra
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Parkinson Disease Drug Therapy
• Improves functional ability and clinical status of patients
• Aims at symptomatic relief, does not alter disease process. No cure.
• Temporary or prolonged remission
• Side effects can be a problem
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Drug ListAnti-Parkinson Agents
– amantadine (Symmetrel)– benztropine (Cogentin)– bromocriptine (Parlodel)– entacapone (Comtan)– levodopa (Dopar)– levodopa-carbidopa (Sinemet)
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Drug ListAnti-Parkinson Agents
– levodopa-carbidopa-entacapone (Stalevo)
– pramipexole (Mirapex)– rasagiline (Azilect)– ropinirole (ReQuip)– selegiline (Eldepryl)– tolcapone (Tasmar)
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levodopa (Dopar)
• Metabolized to dopamine in brain, but brain does not receive a full dose
• Very undesirable effects, including nausea, vomiting, cardiac arrhythmia
• After about 5 years of therapy, 2/3 of patients experience on-off phenomenon
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levodopa-carbidopa (Sinemet)
• Probably most common drug used in Parkinson disease
• Carbidopa allows for lower doses of levodopa to be used which decreases side effects
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rasagiline (Azilect)
• Monoamine oxidase inhibitor (MAOI), blocks breakdown of dopamine
• Initial therapy to improve symptoms
• Possible hypertensive crisis if patient consumes foods with tyramine (aged cheeses, cured meats, soy sauce)
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entacapone (Comtan)
• Second in class of anti-Parkinson agents known as catechol-O-methyl transferase (COMT) inhibitors
• Indicated for patients who have a deteriorating response to levodopa
• Less toxic than tolcapone (Tasmar)
• Taken without regard to food
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Terms to Remember
Parkinson disease
basal nuclei
substantia nigra
on-off phenomenon
catechol-O-methyl transferase (COMT)
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Other Central Nervous System Disorders
• Myasthenia gravis
• Attention-deficit hyperactivity disorder and attention-deficit disorder
• Amyotrophic lateral sclerosis (ALS)
• Multiple sclerosis (MS)
• Alzheimer disease
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Myasthenia Gravis
• Autoimmune disorder of the neuromuscular junction
• ACh receptors are destroyed at the motor end plate
• Characterized by weakness and fatigability, especially of skeletal muscles
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Motor End Plate
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Presenting Signsof Myasthenia Gravis
• Ptosis (drooping eyelid)
• Diplopia (double vision)
• Dyarthria (speech)
• Dysphagia (swallowing)
• Extremity weakness
• Respiratory difficulty
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Treatment of Myasthenia Gravis
• Acetylcholinesterase drugs can produce improvements in all forms of myasthenia gravis
• Drug therapy does not inhibit or reverse the immunologic flaw
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Drug ListAgents for Myasthenia Gravis
– azathioprine (Imuran)– cyclophosphamide (Cytoxan)– edrophonium (Enlon, Reversol)– neostigmine (Prostigmin)– pyridostigmine (Mestinon)
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pyridostigmine (Mestinon)
• Blocks destruction of ACh
• Allows for ACh accumulation at the synaptic junction
• Take with food or milk and at same time each day
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cyclophosphamide (Cytoxan)
• Prevents cell division by targeting the auto-immune portion of the disease
• Use chemotherapeutic precautions
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Attention-Deficit Disorders
• Attention-Deficit Hyperactivity Disorder (ADHD)
• Attention-Deficit Disorder (ADD)
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Attention-Deficit Hyperactivity Disorder (ADHD)
• Neurologic disorder characterized by hyperactivity, impulsivity, and distractability
• Symptoms can persist into adult life
• Most drugs used are amphetamines and amphetamine derivatives, C-II
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Drug ListAttention-Deficit Disorders Agents
– atomoxetine (Strattera)
– dexmethylphenidate (Focalin), C-II
– dextroamphetamine-amphetamine (Adderall), C-II
– lisdexamfetamine (Vyvanse)
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Drug ListAttention-Deficit Disorders Agents
– methylphenidate (Concerta, Daytrana Metadate, Metadate ER, Methylin, Ritalin, Ritalin-SR), C-II
– modafinil (Provigil, Sparlon)
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Dispensing Issues of Attention-Deficit Disorders Agents
• ADHD drugs used for treatment as a group must provide a medication guide to patient or caretaker
• Technicians—check for mediation guide when drug is handed to patient or caretaker, even if drug is not C-II
Warning!
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atomoxetine (Strattera)
• Nonstimulant indicated for treatment of ADHD in patients 6 years and older
• Controls impulsivity and activity
• Not a controlled substance, refills can be called in
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methylphenidate (Concerta, Daytrana Metadate, Metadate
ER, Methylin, Ritalin, Ritalin-SR)
• Drug of choice to treat attention-deficit disorders
• CNS stimulant, C-II controlled substance• Improved dosage allows the drug to be
taken only in the morning• One form comes in a patch, improving
compliance
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methylphenidate (Concerta)
• Dosed once a day, in morning
• Outer layer dissolves to release part of drug immediately
• Rest of drug is OROS tablet– Slowly releases through pores in tablet,
leaving a ghost
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methylphenidate (Daytrana Metadate)
• Patch form of methylphenidate
• Worn for 9 hours, then removed
• Drug is in the adhesive
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dextroamphetamine-amphetamine (Adderall)
• C-II controlled substance
• Effects last about 6 hours
• Primary side effect is depression as drug wears off
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Dispensing Issues of Adderall
• Look-alike and sound-alike– Adderall (ADHD)– Inderal (propranolol), beta blocker used
to treat anxiety
Warning!
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Modafinil (Provigil, Sparlon)
• Sparlon is nonstimulant medication
• Indicated for treatment of ADHD in patients 6 years and older
• Increases mental alterness
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Amyotrophic Lateral Sclerosis (ALS)
• Also known as Lou Gehrig disease
• Progressive degenerative disease of the nerves
• Muscle weakness, paralysis, and eventually death
• Cause: excessive levels of glutamate
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Drug ListAgent for Amyotrophic Lateral Sclerosis
– riluzole (Rilutek)
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riluzole (Rilutek)
• First drug approved for amyotrophic lateral sclerosis
• Inhibits release of glutamate
• Seems to improve survival rate by 3 months in some patients
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Multiple Sclerosis (MS)
• Autoimmune disease in which myelin sheaths around nerves degenerate
• Patient loses use of muscles, and often eyesight is affected
• Some drugs can slow progression
• No cure
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Drug ListMultiple Sclerosis Agents
– baclofen (Lioresal)– glatiramer acetate (Copaxone)– interferon beta-1a (Avonex, Rebif)– interferon beta-1b (Betaseron)– mitoxantrone (Novantrone)– tizanidine (Zanaflex)
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glatiramer acetate (Copaxone)
• Seems to block the autoimmune reaction against myelin that leads to nerve damage
• Decreases frequency of relapses
• Not been shown to slow disease progress
• Given everyday by subcutaneous injection
• Must be frozen
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tizanidine (Zanaflex)
• Indicated to reduce muscle spasticity in MS and spinal cord injuries
• Oral drug
• Side effects: dry mouth, sedation, dizziness, and hypotension
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Alzheimer Disease
• Progressive form of dementia
• Changes personality and behavior
• No treatments can cure or reverse
• Drugs can slow the disease
• Depression often treated with antidepressants according to symptoms
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Progression of Alzheimer Disease
1. Memory deficit, forgetfulness, misplacements of ordinary items
2. Inability to complete complex tasks
3. Complete incapacitation, disorientation, and failure to thrive
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Drug ListAgents for Alzheimer Disease
– donepezil (Aricept)– galantamine (Razadyne)– ginkgo (many)– memantine (Namenda)– rivastigmine (Exelon)– tacrine (Cognex)
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tacrine (Cognex)
• Cholinesterase inhibitor
• Most common side effect: increase in liver lab values
• Taken 4x a day on an empty stomach
• Side effects: nausea, vomiting
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donepezil (Aricept)
• Convenient to use
• Few side effects
• Improves memory and alertness
• Give once a day at bedtime
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Dispensing Issue of Aricept
• Look-alike and sound-alike– Aricept– Aciphex (rabeprazole), GERD
Warning!
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memantine (Namenda)
• May have fewer side effects and better tolerated than other drugs
• Evidence that this drug slows advancement of Alzheimer disease
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Terms to Remember
myasthenia gravis
motor end plate
ptosis
diplopia
dysarthia
attention-deficit hyperactivity disorder (ADHD)
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Terms to Remember
amyotrophic lateral sclerosis (ALS)
Lou Gehrig disease
multiple sclerosis (MS)
Alzheimer disease
gingko
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Assignments
• Complete Chapter Review activities• Answer questions in Study Notes
document• Study Partner
– Quiz in review mode– Matching activities– Drug tables