Pharmacology - CNS Drugs - Dopaminergic Agents Flashcards
Hyperfunctioning (dopamine) in the mesolimbic pathway causes:
Addiction, hallucination
Hyperfunctioning (dopamine) in the mesocortical pathway causes:
Hypervigilance
Hyperfunctioning (dopamine) in the tuberoinfundibular pathway causes:
Hypoprolactinemia
Parkinsonism is hypodopamine in what brain area?
Nigrastriatal system
What is the main theory behind high or low dopamine functioning?
If you inherit an abnormal gene (val substitution), then you have aggressive COMT (catechol-O-methyltransferase) and break down too much dopamine and develop symptoms
What is Levodopa?
- Precursor to DA
- Crosses BBB (and is converted to DA; improves nigrostriatal functioning)
- 1st line tx for Parkinson’s unless pt young (want to delay as long as possible)
What drug is often used in combination with Levodopa, and why?
- Carbidopa
- b/c it prevents peripheral dopamine activity and lowers fatigue, dizziness, and nausea SEs
Give the side effects: Levodopa
- If too much dopamine –> psychosis, mania, dyskinesias (abnormal, involuntary movements)
- Hypotension, syncope, nausea, anxiety/agitation, fatigue
People with the T-allele for folate metabolism have less of what chemical that may contribute to depression?
- less dopamine
- T allele = faulty methylhydrofolate reductase enzyme (MTHFR) –> less DA
- “you don’t want to have T (allele for MTHFR) with Val (substitution –> abn, aggressive COMT)”
What is the mechanism of action of Norepinephrine Dopamine Reuptake Inhibitors (NDRIs)?
- NDRIs block the dopamine transporter (aka dopamine reuptake inhibition)
- Leaves more DA in the synapse to increase to increase DA in the mesocortical pathway
- Can lower depression symptoms
- Buproprion is an example
Give the side effects of NDRIs.
Insomnia, jitteriness, hypervigilance, seizures, anxiety, dry mouth, palpitations, mild increases in BP, sweating think sympathetic stimulation (NE)
Give the class: dextroamphetamine lisdexamfetamine mixed amphetamine salts
Stimulants
Give the indication: dextroamphetamine lisdexamfetamine mixed amphetamine salts
ADHD
What is the mechanism of action of the stimulant class?
Stimulants block the DAT like buproprion, and may even reverse it, and increase vesicular monoamine transport (VMAT2) , ejecting more DA from nerve terminals
What is the mechanism of action of methylphenidate?
block DA transporter less effective than the stimulants
Give the class: Modafinil; Armodafinil
Stimulants Different MOA than amphetamine
Give the indications: Modafinil; Armodafinil
Narcolepsy, Apnea, Shiftwork disorder NOT ADHD approved Less severe side effects
What are unique side effects of Modafinil; Armodafinil?
May lower birth control effectiveness bc may increase p450-3A4 enzymes
Give the mechanism of action: Modafinil, Armodafinil
Increases histamine activity in the tuberomammilary nucleus; may block DAT May increase orexin activity
What are side effects of stimulants?
Psychosis at high doses Addiction Weight loss DA and NE side effects at any dose
Monoamine Oxidase Enzymes A and B are responsible for breaking down:
Dopamine and other monoamines like NE and serotonin
Give the mechanism of action: MAOi
Block the breakdown of DA
Give the indication for Selegiline.
Parkinson’s Depression MAO-B inhibitor at low dose, full MAO-A and B at higher dose (patch)
Give the indication for Rasagiline.
Parkinson’s MAO-B inhibitor
Give the mechanism of action: Tranylcypromine (Parnate); Isocarboxazid (Marplan); Phenelzine (Nardil)
Irreversibly inhibit both MAO-A and MAO-B
Give the side effects: MAOi
Hypotension, dizziness, insomnia, weight gain Hypertensive crisis (with tyramine-rich foods); serotonin syndrome (MAOI + SSRI)
What things in combination with MAOi use can precipitate a hypertensive crisis?
Tyramine-rich foods such as cheeses, fava beans or fermented things; Nasal decongestants NE-based antidepressants
Give two examples of COMT inhibitors.
Entacapone (nausea and fatigue) Tolcapone (not used anymore bc of liver failure) Catechol-O-methyltransferanse inhibitors COMT is an enzyme that degrades monoamines. Inhibit this enzyme to increase DA or NE Used to help treat Parkinson’s
D2 receptor agonism increases DA activity mainly in the nigrastriatal pathway. In this way, it is therapeutically indicated for what diagnosed?
Parkinson’s Restless Leg Syndrome
Give the class: Bromocriptine
Ergot D2 receptor agonist
Give the class: Pramipexole (Mirapex); Ropinerole
Selective D2 receptor agonist
Give the class: Apomorphine
D2 receptor agonist
Give the class: Aripiprazole (Abilify)
D2 & D3 receptor (partial) agonist
Give the class: Amantadine
Antiviral
Bromocriptine, Pramipexole, Ropinerole and Apomorphine are all used to treat mild Parkinson’s and RLS. What other diagnosis is indicated specifically for Bromocriptine?
Hyperprolactinemia
Give the indication: Aripiprazole
Schizophrenia and depression Antipsychotic
Give the indication: Amantadine
Mild Parkinson’s (2nd-line); influenza
Give the side effects: Amantadine
Nausea, dizziness, psychosis, insomnia, seizures