Enzymes in Biological Processes
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Questions and Answers

What is the primary mechanism of action of COMT inhibitors in the management of Parkinson's disease?

  • Inhibition of voltage-activated Na+ channels
  • Enhancement of GABA-mediated synaptic inhibition
  • Antagonism of AMPA or NMDA receptors
  • Inhibition of Catechol-O-methyl transferase (COMT) (correct)

    • Which of the following acetylcholine receptor antagonists is known to have favorable effects on rigidity and bradykinesia?

  • Entacapone
  • Trihexyphenidyl
  • Tolcapone
  • Benztropine (correct)

    • What is a significant adverse effect of tolcapone that requires close monitoring?

  • Diarrhea
  • Brown-orange urine discoloration
  • Hepatotoxicity (correct)
  • Orthostatic hypotension

    • Which anti-epileptic drug has a mechanism of action involving the inhibition of voltage-activated Na+ channels?

    <p>Phenytoin</p> Signup and view all the answers

    What is the primary reason for adjusting total phenytoin levels?

    <p>Protein binding</p> Signup and view all the answers

    Which of the following is a significant interaction of SSRIs?

    <p>MAOIs</p> Signup and view all the answers

    What is a common adverse effect of acetylcholine receptor antagonists?

    <p>Urinary retention</p> Signup and view all the answers

    What is the target concentration of free phenytoin in the blood after 5 days of dosing?

    <p>1-2 mcg/mL</p> Signup and view all the answers

    Which COMT inhibitor is combined with levodopa/carbidopa in the medication Stalevo?

    <p>Entacapone</p> Signup and view all the answers

    What is the primary mechanism of action of SSRIs?

    <p>Inhibition of reuptake of serotonin</p> Signup and view all the answers

    What is the primary function of Acetylcholinesterase in the body?

    <p>To hydrolyze Acetylcholine</p> Signup and view all the answers

    What is the mechanism of action of Memantine?

    <p>It attenuates the excitotoxic effects of glutamate</p> Signup and view all the answers

    What is the primary advantage of using Rytary over Sinemet CR?

    <p>It can be opened and sprinkled</p> Signup and view all the answers

    What is the primary function of Carbidopa?

    <p>To inhibit the conversion of levodopa to dopamine in peripheral tissues</p> Signup and view all the answers

    What is the primary reason for combining Levodopa with Carbidopa?

    <p>To decrease the incidence of peripheral conversion of levodopa</p> Signup and view all the answers

    What is the primary advantage of using Acetylcholinesterase Inhibitors in the treatment of Alzheimer's disease?

    <p>They preserve memory, learning, and attention</p> Signup and view all the answers

    What is the primary reason for the wearing off phenomenon of Levodopa?

    <p>Loss of efficacy over time due to increased conversion in peripheral tissues</p> Signup and view all the answers

    What is the primary difference between Donepezil and Galantamine?

    <p>Donepezil is available in a transdermal patch, while Galantamine is not</p> Signup and view all the answers

    What is the primary mechanism of action of Rivastigmine?

    <p>It selectively inhibits cholinesterase in the CNS</p> Signup and view all the answers

    What is the primary adverse effect of Memantine?

    <p>Headache, confusion, dizziness, hallucinations</p> Signup and view all the answers

    What is the frequency of administration for IM available antipsychotics?

    <p>Every 4 or 6 weeks</p> Signup and view all the answers

    Which of the following antipsychotics is associated with a higher risk of agranulocytosis?

    <p>Clozapine</p> Signup and view all the answers

    What is the primary reason for monitoring A1C periodically in patients treated with atypical antipsychotics?

    <p>Risk of diabetes mellitus</p> Signup and view all the answers

    Which of the following antipsychotics is approved for the treatment of agitation associated with dementia due to Alzheimer's disease?

    <p>Brexpiprazole</p> Signup and view all the answers

    What is a common neurological side effect of antipsychotics?

    <p>Sedation</p> Signup and view all the answers

    Which of the following antipsychotics is known to cause the most weight gain?

    <p>Clozapine</p> Signup and view all the answers

    What is a characteristic of newer second-generation antipsychotics, such as Brexpiprazole and Cariprazine?

    <p>They have a more complex mechanism of action</p> Signup and view all the answers

    Which of the following antipsychotics can be used for the treatment of bipolar disorder?

    <p>All of the above</p> Signup and view all the answers

    What is a common cardiovascular side effect of antipsychotics?

    <p>Prolongation of QT interval</p> Signup and view all the answers

    What is the primary reason for continuing PO treatment during the first 3 weeks when transitioning to IM antipsychotics?

    <p>To overlap with the IM formulation</p> Signup and view all the answers

    What should be done when switching from a SSRI to a MAOI?

    <p>Wait 2 weeks after stopping SSRI before starting a MAOI</p> Signup and view all the answers

    What is the mechanism of action of bupropion?

    <p>Blocks the reuptake of dopamine and norepinephrine</p> Signup and view all the answers

    What is the most significant adverse effect of brexanolone?

    <p>Sedation/loss of consciousness</p> Signup and view all the answers

    What is the term for the symptoms of schizophrenia that are not present in normal individuals?

    <p>Positive symptoms</p> Signup and view all the answers

    What is the mechanism of action of typical antipsychotics?

    <p>Dopamine receptor blockers</p> Signup and view all the answers

    What is the term for the symptoms of schizophrenia that are present in normal individuals but are diminished in schizophrenia?

    <p>Negative symptoms</p> Signup and view all the answers

    What is the drug that is chemically identical to allopregnanolone and is used to treat post-partum depression?

    <p>Brexanolone</p> Signup and view all the answers

    What is the time frame for improvement in hallucinations and disturbances with antipsychotic treatment?

    <p>Late &gt; 8 weeks</p> Signup and view all the answers

    What is the mechanism of action of aripiprazole?

    <p>Partial D-2 agonist, 5HT-1A agonist, 5HT-2A antagonist</p> Signup and view all the answers

    What is the SSRI that is least likely to cross into breast milk?

    <p>Sertraline</p> Signup and view all the answers

    Study Notes

    Enzymes

    • Enzymes typically end in –ASE
    • Acetylcholinesterase (AChE) is responsible for hydrolyzing Acetylcholine (ACh) and decreases the amount of ACh

    Acetylcholinesterase Inhibitors

    • Selectively inhibit cholinesterase in the CNS
    • Increase Ach concentrations in the cerebral cortex
    • May slow deterioration of cognitive function and preserve memory, learning, and attention
    • Examples of agents: Donepezil (Aricept), Rivastigmine (Exelon), Galantamine (Razadyne)
    • Adverse effects: Memantine (Namenda) - constipation, headache, confusion, dizziness, hallucinations, hypertension

    Levodopa

    • Biosynthetic precursor of dopamine
    • Increases the concentration of dopamine in the brain
    • Metabolized in peripheral tissue by Decarboxylase and Catechol-O-methyl transferase (COMT)
    • Adverse effects: nausea, vomiting, orthostatic hypotension, sedation, depression, delirium, paranoia, delusions, hallucinations
    • Always given in combination with carbidopa (Sinemet, Sinemet CR, Parcopa)

    Carbidopa

    • MOA: Decarboxylase Inhibitor
    • Inhibits conversion of levodopa to dopamine in peripheral tissues
    • Increases the amount of levodopa that enters the brain
    • Decreases GI and cardiovascular adverse effects due to less conversion in peripheral tissue

    COMT Inhibitors

    • Inhibits peripheral metabolism of levodopa through inhibition of Catechol-O-methyl transferase (COMT)
    • Used in combination with levodopa/carbidopa to enhance its effectiveness and manage wearing off
    • Examples of agents: Tolcapone, Entacapone, Opicapone
    • Adverse effects: Hepatotoxicity (tolcapone), orthostatic hypotension, diarrhea, hallucinations, brown-orange urine discoloration (benign)

    Acetylcholine Receptor Antagonists

    • Mechanism of action: Competes with Ach at muscarinic receptors (anticholinergic)
    • Helps reduce tremor
    • Adverse effects: sedation, depression, confusion, dry mouth, blurred vision, constipation, urinary retention

    Antiepileptic Drugs

    • Four primary mechanisms: Inhibit voltage-activated Na+ channels, inhibit voltage-activated Ca2+ channels, enhance GABA-mediated synaptic inhibition, and attenuate Glutamate-mediated excitatory responses
    • Examples of agents: Phenytoin (Dilantin), Phenytoin Pharmacokinetics - half-life ~ 24 hours, highly protein bound, metabolized by the liver, dose-dependent (Michaelis-Mentin also known as non-linear kinetics)

    SSRIs

    • Adverse effects: cardiovascular (QT prolongation with citalopram and escitalopram), withdrawal syndrome (GI complaints, flu-like symptoms, anxiety, insomnia)
    • Drug interactions: MAOIs, TCAs, SNRIs, 5HT over-the-counter supplements
    • Examples of agents: Bupropion (Wellbutrin), Venlafaxine (Effexor), Desvenlafaxine (Pristiq), Duloxetine (Cymbalta), Milnacipran (Savella)

    SNRIs

    • Bind to serotonin (SERT) and norepinephrine (NET) transporters
    • Prevent reuptake of both 5HT and NE (selective for NE)
    • Adverse effects: hypertension, sexual dysfunction, insomnia, nausea

    Depression in Pregnancy

    • Reported in 14 to 23% of pregnant patients
    • Mild to moderate depression: Discontinue pharmacotherapy unless severe history, Cognitive behavioral therapy/interpersonal psychotherapy
    • Severe depression: Initiate/continue pharmacotherapy, Sertraline (least likely to cross into breast milk)

    Brexanolone (Zulresso)

    • Post-partum depression
    • MOA: Allosteric modulator of GABAa
    • Chemically identical to allopregnanolone
    • Restores dysregulated neural network activity associated with depression
    • One-time 60-hour infusion
    • Adverse effects: sedation/loss of consciousness (dose-related), start in AM to best assess degree of sedation

    Schizophrenia

    • Positive (+) symptoms: delusions, hallucinations, disorganized speech, unusual behavior, hostility, excitement, grandiosity
    • Negative (-) symptoms: blunted affect, lack of motivation and pleasure, emotional withdrawal, uncooperativeness, social withdrawal, poverty of speech
    • Antipsychotic class: Dopamine (D2) receptor blockers, Serotonin (5-HT2) receptor agonist/antagonist
    • Typical antipsychotics: Phenothiazines (Chlorpromazine, Fluphenazine, Thioridazine, Perphenazine, Trifluoperazine), Thioxanthenes (Thiothixene), Butyrophenones (Haloperidol)
    • Atypical antipsychotics: Clozapine (Clozaril), Loxapine (Loxitane), Olanzapine (Zyprexa), Quetiapine (Seroquel), Ziprasidone (Geodon), Aripiprazole (Abilify), Aristada (IM), Asenapine (Saphris), Iloperidone (Fanapt), Lurasidone (Latuda), Risperidone (Risperdal), Paliperidone (Invega)
    • Adverse effects: weight gain, impaired glucose tolerance, clear risk of diabetes mellitus, sexual dysfunction, hematologic (clozapine may cause agranulocytosis)

    Newer Second Generation Antipsychotics

    • Brexpiprazole (Rexulti)
    • Cariprazine (Vraylar)
    • Both have complex (theoretically better targeted) mechanisms of action (sub-receptors)
    • Similar side effect profile to Aripiprazole
    • Brexpiprazole: slightly more weight gain seen in MDD studies but less EPS symptoms

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    Learn about enzymes, specifically Acetylcholinesterase, and their role in biological processes such as neurotransmission and cognitive function. Understand how Acetylcholinesterase Inhibitors work to increase Ach concentrations and preserve memory, learning, and attention.

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