Dopaminergic Agents Flashcards
List the 5 dopamine pathways.
Nigrostriatal, Mesolimbic, Mesocortical, Tuberoinfundibular, Thalamic (?)
Nigrostriatal pathway?
Controls movement – Projects from SN to BG of striatum as part of the extrapyramidal nervous system.
Mesolimbic pathway?
Controls reward and perception – Projects from the midbrain ventral tegmental area to the nucleus acccumbens as part of the limbiv system.
Mesocortical pathway?
Controls executive function – Projects from the midbrain ventral tegmental area to the prefrontal cortex (DLPFC - cognition & VMPFC - affect)
Tuberoinfundibular pathway?
Controls pituitary prolactin function – Projects from the hypothalamus to the anterior pituitary gland and controls prolactin secretion.
Hyper/o/functioning mesolimbic?
Addiction/hallucinations vs. Amotivation/apathy
Hyper/o/functioning mesocortical?
Hypervigilance vs. Inattention
Hyper/o/functioning nigrostriatal?
Dyskinetic movement vs. Parkinsonism
Hyper/o/functioning tuberoinfundibular?
Hypoprolactinemia vs. Hyperprolactinemia
Levodopa mxn and for?
Precursor to DA, crosses BBB, converted to DA proper in the CNS, improve nigrostriatal functioning, promote better movement in Parkinson’s syndrome
Levodopa side effects?
At too high doses, creates dyskinetic movements and hallucinations, mania, psychosis. On average: hypotension, syncope, nausea, anxiety/agitation, fatigue.
Cardiodopa mxn?
Inhibits peripheral conversion of L-DOPA to DA (does not cross BBB) – Prevents peripheral DA effects and lowers side effects (fatigue, dizziness, nausea)
What happens after many years of use with levodopa?
After many years, wears off (as such, it is first line treatment unless the patient is very young).
If depression is a low dopaminergic state due to inadequate 1 C cycling, what could be given?
L-methylfolate or S-adenosyl methionine (Both allow 1 C cycle to run and increase DA production)
Side effects of L-methylfolate or S-adenosyl methionine (“1 C neutriceuticals”) ?
Essentially none, possible GI upset
Bupropion mxn?
NE-DA reuptake inhibitor: Blocks dopamine transporter (DAT)
Bupropion for?
Depression
Bupropion side effects?
Insominia, jitteriness/hypervigilance, seizures, sympathetic stimulation (insominia, anxiety, agitation, nausea, dry mouth, sweating, palpitations, increased BP), NOT addicitve
Amphetamines mxn?
Block DAT, reverse DAT, increase vesicular monoamine transport (VMAT2) ejection of DA
Amphetamines for?
ADHD
List the most aggressive amphetamines.
Dextroamphetamine, mixed amphetamine salts, lisdexamfetamine.
What is unique about lisdexamfetamine?
Prodrug
Are amphetamines addictive?
Yes
What about methylphenidate?
Just blocks the DAT
“Pseudostimulants?”
Modafinil/Armodafinil
What class are pseudostimulants?
Class IV addictive drugs (“less” addictive)
Modafinil/Armodafinil for?
Fatigue (due to narcolepsy, apnea, shiftwork) – NOT ADHD
Modafinil/Armodafinil side effects?
Less severe but similar to other stimulants. Increase p450-3A4 and lower BC effectiveness
Modafinil/Armodafinil mxn?
Increase Histamine in the tuberomammilary nucleus (TMN) and activate alertness in the frontal cortex. Increase orexin. Manipulate noradrenergic receptor post-synaptically.
Modafinil/Armodafinil effectiveness requires?
An operating DAT system
In general, stimulant side effects?
Because of involvement of mesolimbic pathway: Addiction. “Super high” doses: Psychosis. “Moderate” doses: Appetite and weight loss. Any dose: NE or DA side effects.
Selegiline mxn?
MAO-BI at low doses, MAOA+BI at high doses
Selegiline for?
Parkinson’s (B), Depression (A + B)
Rasagiline mxn?
MAOBI
Rasagiline for?
Parkinson’s
Is MAOA or B more relevant for DA?
B
MAOA & B Inhibitors? For what?
For depression: Isocarboxazid, Phenelzine, Tranylcypromine, Selegiline
MAOI side effects?
Hypotension, dizziness, insomnia, weight gain. Those for depression have greater effects, interfering with ability to breakdown seretonin and NE (drug-drug interactions)
How does a HTN crisis happen with an MAOI?
Addition of a drug that raises NE will elevate BP (not necessarily a crisis). Addition of a food source with tyramine causes immediate release of NE stores created the HTN crisis (MAOA is used to breakdown tyramine)
Foods with tyramine?
Smoked meets, aged cheese, tofu, fava beans, pickled herring, banana peel, spoiled meat/fish, marmite
Seretonin syndrome symptoms? Caused how?
Tremor, muscle spasm, inc/dec vitals, hyperthermia, delirium, coma, death. MAOIs decrease seretonin breakdown, so addition of an aggressive serotonin drug (antidepressant, narcotics, some antihistamines) creates toxic levels.
COMTIs?
Entacapone, Tolcapone
COMTIs for?
Parkinson’s
What does COMT do?
Catechol-o-methyltransferase degrades monoamines in the synapse.
Entacapone side effects?
Nausea, fatige
Tolcapone side effects?
Liver failure
Is D2 tonic or phasic?
Phasic
Is D3 tonic or phasic?
Tonic
D2 receptor agonists for?
Parkinson’s, Restless Legs Syndrome
D2 receptor agonists?
Bromocriptine, Pramipexole, Ropinerole, Apomorphine injections
D2 receptor agonist side effects?
Nausea, fatigue, dizziness, mania
D3 agonist?
Aripiprazole
Aripiprazole for?
Schizophrenia, Depression
Aripiprazole mxn?
Partial D3 agonists, Partial D2 agonist
Amantadine for?
Parkinson’s, Flu, Malaria
Amantadine mxn?
Release DA from terminal vesicles, block DAT, stimulate D2
Amantadine side effects?
Nausea, dizziness, psychosis, insominia, seizures
Reserpine mxn?
Blocks VMAT so that vesicles with monoamines cannot be released
Reserpine for?
HTN (less NE), Theoretically, less DA, so decreased psychosis
Tetrabenzine mxn?
Block VMAT, vesicles with monoamines cannot be released into synapses
Tetrabenzine for?
Huntington’s chorea
“Schizophrenia meds?”
D2 receptor antagonists: 1st generation antipsychotics = Typicals/FGAs & 2nd generation antipsychotics = Atypicals/SGAs
FGA mxn?
Non-selective D2 receptor antagonists in all DA pathways
FGA drug classes?
High potency/High affinity & Low potency/Low affinity
FGA high potency side effects?
Extrapyramidal Syndromes (EPS) when DA is too low: Akathisia (restlessness), dystonia, parkinsonism, neuroleptic malignant syndrome (hyperthermia, muscle rigidity, vital sign instability, rhabdomyolysis)
Why do anticholinergics help Parkinson’s?
Inhibiting cholinergic tone in the BG improves DA flow in the nigrostriatal pathway
Anticholinergics for?
Early Parkinson’s, but most effective in treating EPS caused by FGAs/SGAs
Anticholintergics used?
Benztropine, diphenhydramine, trihexyphenadyl
Side effects of anticholinergics?
Dry mouth, blurred vision, tachy, constipation, confusion, delirium, hallucinations
What is tardive dyskinesia? When does it happen?
Permanent movement disorder with choreic movements &/or athetotic movements, caused by chronic D2 receptor antagonism
FGA low potency side effects?
EPS, H1 receptor antagonism (fatigue, increased appetite/weight), anticholinergic muscarinic antagonism (dry mouth…), NE a1 antagonism (orthostasis), LOWER risk for TD
FGA high potency drugs?
Haloperidol, Fluphenazine, Thiothixine
FGA low potency drugs?
Chlorpromazine, Thioridazine
SGA mxn? Significance of added effect?
D2 receptor antagonism AND Serotonin 2a (5HT2a) antagonism. This loweres EPS risk. All in all, greater blocking of DA in the mesolimbic system and better transmission in all other DA pathways
SGAs may help what besides schizophrenia?
Depression, anxiety, autism, mania in bipolar
SGA ‘dones?
Risperidone, paliperidone, ziprasidone, iloperidone, lurasidone
SGA ‘pines?
Olanzapine, quetiapine, asenapine, clozapine (antagonizes D4 and D1 too)
SGA ‘rips/’pips?
Aripiprazole (partial agonist @ D2 and D3)
Side effects of ‘dones?
More EPS
Side effects of ‘pines?
More sedating (antihistamine effect), More metabolic syndrome
SGA boxed warnings?
Suicide < 25, Metabolic syndrome, TD/EPS, stroke in dementia patients
Clozapine mxn?
D2, 5HT2a antagonist, D1, D4 antagonist
Clozapine for?
Refractory schizophrenia
Clozapine risk?
agranulocytosis: requires WBC and ANC monitoring, most metabolic risk of any agent, but little to no EPS/TD risk
What is the most effective antipsychotic?
Clozapine