CNS Drugs - Exam 3 Flashcards
Levodopa/ Carbidopa (Sinemet)
Dopamine Replacement
Mech: Levodopa is carrried across BBB, increases synth of dopamine in CNS
Restores balance btwn ACh & dopamine
Carbidopa protects breakdown of Levodopa in GI tract!
Use: Will only alleviate symptoms slightly, will not stop progression of Parkinson’s.
SE: “NOT PD”
Nausea & vomiting (Stim of dopamine receptors)
-Ortho hypoT
-Tardive dyskinesia in about 80% pts,
typically indicates they’re taking too much!
-Psychosis in 20%
-Dark sweat & urine (can stain clothing, non-toxic)
Notes: If taken w/ MAOIs can cause hypertensive crisis!
Pramipexole (Mirapex)
Ropinirole (Requip)
Dopamine Agonists “-ole”
Mech: Activate dopamine receptors in CNS , inhibits release of GABA
Use: Alt to levodopa/carbidopa for younger pts
SE: “IS NO PD”
Impaired impulse control in 50%
-Somnolence/sleep attacks
-Nausea & vomiting
-Ortho hypoT
-Psychosis
-Dizziness
Entacapone (Comtan)
COMT inhibitors
Mech: Inhibits COMT -> increases concentration of levodopa & dopamine , less imbalance btwn ACh & dopamine
Use: Parkinson’s
SE: “NOT PD”
-Nausea
-Ortho hypoT
-Tardive Dyskinesia
-Psychosis/hallucinations
-Discoloration of urine
Off times of motor drugs
Gradual vs Abrupt
Gradual = slow loss of effect of drug as it “wears off” near the end of its dosing interval.
Solution = shorten dosing interval (give drug sooner)
Abrupt = “on/off” loss of effect. Can occur at ANY time in dosing interval. Lasts from mins to hrs. No relation to concentration of the drug.
Solution = add another Parkinson’s drug
Selegiline (Eldepryl)
MAO-B Inhibitors
Mech: Blocks MAO-B which is SPECIFIC to dopamine.
Results in less breakdown of dopamine = increased lvls
Use: Parkinson’s
SE: Insomnia – due to CNS excitation from dopamine
- Ortho hypoT
- Dizziness
Notes: DO NOT consume foods high in Tyramine! Monitor pts BP!
Amantadine
(Symmetrel)
Mech: not well understood, may stim dopamine receptors?
Use: alt to levodopa/carbodopa If tremor is the presenting symptom of PD
SE: “Amanda was sooo scared that there IS NO PD”
- Impaired impulse control
- Skin molting (livedo reticularis)
- Nausea & vomiting Most common
- Ortho hypoT
- Psychosis
- Dizziness
Benzotropine (cogentin)
Centrally acting Anticholinergic
Mech: blocks effect of ACh in CNS, improves balance btwn ACh & Dopamine , reduces tremors
Use: Parkinson’s
SE: Anticholinergic effects
- Blurred vision
- Dry mouth
- Urinary retention
- constipation
- Tachycardia
Careful in pt with glaucoma
Donezepil (Aricept)
Rivastigmine (Excelon)
Alzheimer Drugs, Cholinesterase inhib
Mech: prevents the breakdown of ACh by blocking cholinesterase, higher levels of ACh = more neuron impulses
Use: most common drugs for AD
Only effective in about 1in12 people
SE: Cholinergic effects
- Nausea & vomiting
- Diarrhea
- bronchoconstriction Careful with asthma
Memantine (Namenda)
NMDA receptor antagonist
Mech: Takes the place of Mg blocking the entry of Ca into neuron. When there’s a LARGE amount of glutamate released into synapse, NMDA antagonist displaces and allows Ca to enter neuron. Corrects the problem of Ca constantly leaking into neuron in Alzheimer’s.
Use: Alzheimer’s
SE: tolerated well, Dizziness
Aduncanumab (Aduhelm)
monoclonal ab
Mech: Mab that targets beta amyloid
Reduces formation of b-amyloid plaques
Use: Alzheimer’s
SE: Amyloid-related imaging abnormalities (ARIA) ie. microhemorrhages & cerebral edema
Phenytoin (Dilantin)
Fosphenytoin (Cerebryx)
pro-drug of phenytoin
Mech: Selective inhibition of Na channels
Use: anti-epileptic drug
SE: “PHENYTO”
- Purple glove syndrome (if given IV)
- Hyperplastic gingiva
- Excessive sleepiness/sedation
- NYstagmus
- Thrombocytopenia
- Osteoporosis
Bonus: Rash measles like
CYP450 INDUCER!!!!
Carbamazepine
Mech: selective inhibition of Na Channels (same as phenytoin)
Half-life decreases with continued use
Use: monitor drug levels!! 4-12mcg! “Bread” has 4 letters, “bread is a carb” has 12 (4-12)
SE: “BREAD”
- Bone marrow suppression
- Rash (like measles)
- Eye-related (visual) disturbances
- ALT/AST affected (hepatotoxicity)
- Dizziness/drowsiness
Induces CYP450!!
Also is a CYP450 substrate, GRAPEFRUIT juice inhibits metab of Carbamazepine!
Valproic Acid
(Depacon, Depakote, Depakene)
Antiepileptic drugs
Mech: 1. Block Na Channels 2. Blocks Ca influx 3. Increases inhibitory effect of GABA (neuron less likely to depolarize)
Use: Antiepileptic , monitor drug levels 50-100mcg/mL
SE: Dizziness/drowsiness
- GI effects (nausea, vomiting, diarrhea)
- Liver failure – BLACK BOX WARNING (1 in 40,000)
- HIGHLY TERATOGENIC – DO NOT USE IN PREGNANCY
Phenobarbital (Sezaby)
anticonvulsant barbiturate
Mech: Binds to GABA receptors, increases inhibitory power of GABA. Increase effect of GABA at low doses MIMICS effect of GABA at high doses!
Depresses sensory & motor cortex
Use: Anticonvulsant, range 15-40mcg/mL
SE: BLACK BOX WARNING – RISK OF DEPENDENCE OR
WITHDRAWAL
- Dizziness and drowsiness are most common (Effect declines with prolonged use)
- Respiratory depression - often used for SUICIDE
HIGHLY TERATOGENIC
CYP450 INDUCER!!!!!
Gabapentin (Neurontin)
Mech: analog of GABA, appears to bind to receptors on pre-synaptic neuron, blocks the release of excitatory neurotransmitters
SE: Dizziness, Fatigue, Somnolence, Nystagmus,
Edu pt to take at bedtime to reduce effects
Levetiracetam (Keppra)
Mech: Unknown
Use: Drug of choice for seizure management in PREGNANT women
SE: Drowsiness most common!
Diazepam (Valium)
Lorazepam (Ativan)
Midazolam (Versed)
Alprazolam (Xanax)
Benzodiazepines (-azepam or - azolam) , Sedatives
Mech: Potentiate the effect of GABA!
Increase affinity of GABA to receptor
Prolonged sedation in pts with liver fl!
Metabolites are pharmacologically active!
Use: 1st choice for anxiety & insomnia! Less potential for abuse than barbiturates
SE: Tend to be very safe
- CNS depression – somnolence, lightheadedness, poor
concentration
- Retrograde amnesia
- Paradoxical effect – can cause insomnia, excitation, rage
Resp depress when combined with alcohol!
Flumazenil (Romazicon) is used for overdose! It’s a competitive receptor antagonist
Zolpidem (Ambien)
Mech: Also binds to GABA receptor but a softened effect as compared to benzos
Use: only approved for short-term Tx of insomnia
SE: Dizziness & drowsiness
Alcohol
Mech: Stim GABA receptors , Blocks glutamate receptors, Stim serotonin receptors
Use: most commonly used & abused CNS drug
SE: Wernicke’s encephalopathy
• Due to poor absorption of thiamine
• Confusion and nystagmus
• Treated with thiamine replacement
Korsakoff’s psychosis
• Due to poor absorption of thiamine
• Memory disturbances and confabulation (making things up)
• Treated with thiamine replacement
Disulfiram (Antabuse)
Mech: Interferes w/ metab of alcohol by blocking glutathione, increasing concentration of acetaldehyde !
Use: helps alcohols stop drinking
SE: Causes nausea, vomiting, sweating, headache, palpitations when consuming alcohol!
Marijuana
Mech: Highly lipid soluble!! Stims cannabinoid receptors in the brain! Highly concentrated in pleasure, appetite, sensory perception areas of the brain. Believed to stim release of dopamine that triggers reward center!
Use: approved medical uses are:
- Suppression of emesis – particularly for patients receiving chemotherapy
- Appetite stimulation – for patients with AIDS
- Relief of neuropathic pain
SE: Increased HR
- ortho hypoT
– Chronic use a/w bronchoconstriction
– Has been a/w lung cancer
– Reduces spermatogenesis and testosterone levels
– May have effect on babies in utero
– Long term use associated with brain loss in areas a/w memory and attention
Amphetamines
Mech: Increases release of NE and dopamine
Inhibits reuptake of these Neurotransmitters
Use: High potential for abuse
-increases alterness
-reduces fatigue
-Stim respiration
-benefits in ADHD for increased attention = less hyperactivity
SE: Insomnia & restlessness d/t CNS Stim
-Angina
A patient will begin taking immunosuppressant drugs for rheumatold arthritis. The nurse will caution this patient to avoid which dietary supplement?
Echinacea
The nurse is obtaining a history from a patient who discloses daily use of St. John’s wort in addition to prescription drugs. Which effect of this dietary supplement would most concern the nurse?
It accelerates the metabolism of some drugs
