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
