Exam 2 Flashcards
What is depression (definition, symptoms, diagnosis, and prevalence)?
An affective disorder consisting of Major Depressive Disorder (MDD) and related conditions; is a chronic, recurring, and potentially life-threatening illness. It worsens the health of people with other chronic diseases and is associated with increasing diability over time.
Symptoms involve energy, sleep, mood, self-concept, weight, and thoughts of suicide.
Diagnosis is based on a clinical interview and the presence of at least 5 symptoms daily (or almost every day) for at least two weeks.
It is the fourth most disabling disease worldwide.
What age group has the highest depression prevalence?
18-25
How many cases of depression lead to hospitalizations and suicide, and how many cases are adequately treated?
Depression is responsible for 70% of psychiatric hospitalizations
Depression is responsible for 40% of suicides
Only about 21% of yearly cases are adequately treated
What is Major Depressive Disorder (MDD)?
Type of depression characterized by a combination of symptoms that interfere with a person’s ability to work, sleep, study, eat, and enjoy once-pleasurable activites
How often do MDD episodes occur in those with the condition?
An MDD episode may occur only once in a person’s lifetime, but episodes often recur throughout a person’s life; acute episodes of MDD last about 6-14 months untreated
6 types of depression and related conditions
- Major Depressive Disorder (MDD)
- Psychotic depression
- Postpartum depression (10-15% incidence)
- Seasonal affective disorder
- Bipolar disorder
- Dysthymic disorder
What is the paradox of antidepressant medications?
Medications rapidly increase neurotransmitter levels but antidepressant action is slow onset; for this reason, the pathophysiology of depression is thought of as theory rather than fact
What is the current focus of theories of how antidepressants exert their effects (pathophysiology of depression)?
Current theories focus on the long-term effects of antidepressants on the second messenger systems
3 functions of second messenger systems
- Neuron protection from damage due to injury or trauma
- Promote and maintain the health and stability of newly formed neurons
- Promote and maintain synapses that connect neurons
Current theories of the pathophysiology of depression/antidepressants focus on the second messenger systems
How does depression affect the hippocampus?
Long-term depression is associated with a shrinking hippocampus (net loss of neurons); it is thought that this loss of neurons is a mechanism behind depression
What is the relationship between antidepressant drugs and neurogenesis (2 reasons for this)?
Antidepressant drugs increase neurogenesis, and it is thought this is one reason these drugs work.
We know this because:
1. The timing of neurogenesis and net neuron gains in response to antidepressant drugs fits with the time frame of therapeutic response in patients (unlike NT levels)
2. Blocking neurogenesis in mice also blocks the behavioral changes indiced by antidepressant drugs
What is the role of neurotransmitter levels in the pathophysiology of depression?
Role of neurotransmitter levels in the pathophysiology of depression is thought to be through affects on gene expression that alter neurogenesis and neuroprotection (CREB and BDNF interactions)
What is CREB (and relation to BDNF), and what is the relationship between depression and CREB?
Activation of adenylate cyclase and Ca2+ dependent kinase pathways enhance the activity of CREB, a transcription factor that binds to DNA to regulate the expression of other genes.
BDNF is thought to be a key transcriptional target for CREB.
Inadequate neurotransmitter activity for serotonin and/or norepinephrine thought to lead to less CREB and BDNF activity in individuals suffering depression.
What is the relationship between depression and BDNF (3 keys)?
Inadequate neurotransmitter activity for serotonin and/or norepinephrine thought to lead to less CREB and BDNF activity in individuals suffering depression (increased CREB = increased BDNF).
BDNF is thought to be key:
1. BDNF affects the normal development and health of the nervous system
2. Chronic stress decreases the production of BDNF
3. BDNF is decreased in blood levels in depressed patients (reversed with antidepressants)
What are the treatment options for depression (3 first-line drugs, 2 other drugs, and 2 additional approaches)?
First-line drugs:
1. Selective serotonin reuptake inhibitors (SSRIs)
2. Serotonin and norepinephrine reuptake inhibitors (SNRIs)
3. Norepinephrine-dopamine reuptake inhibitor (NDRI)
Other drugs:
1. Tricyclic antidepressants (TCAs)
2. Monoamine oxidase inhibitors (MAOIs)
Additional approaches:
1. Psychotherapeutic interventions
2. Light therapy
6 currently available selective serotonin reuptake inhibitors (SSRIs)
- Fluoxetine (Prozac)
- Paroxetine (Paxil)
- Sertraline (Zoloft)
- Fluvoxamine (Luvox)
- Citalopram (Celexa)
- Escitalopram (Lexapro)
How does serotonin affect different 5-HT (1, 2, 3) receptors?
Serotonin action at 5-HT1 receptors produces antidepressant and anxiolytic effects
Serotonin action at 5-HT2 receptors produces adverse effects including insomnia, anxiety, agitation, sexual dysfunction
Serotonin action at 5-HT3 receptors produces adverse effects including nausea
What are selective serotonin reuptake inhibitors (SSRIs)(mechanism, onset)?
First-line drug for the treatment of MDD, dysthymia, and all anxiety disorders that block the reuptake of serotonin, which increases the amount present in the synapse and magnifies its effects
Although serotonin levels increase quickly, all SSRIs have a slower 4-6 week onset of action
5 side effects and lethality of SSRIs
Side effects:
1. Sexual dysfunction (in up to 80% of patients)
2. Insomnia
3. Anxiety
4. Agitation
5. Nausea
SSRIs are not lethal in overdose
What are the similarities and differences between SSRIs?
Drugs are all considered equally effective, and within and between class switches are considered legitimate; individual differences in metabolism and possible drug interactions are important for patient-to-patient differences in responses to SSRIs
What is serotonin discontinuation syndrome?
Syndrome that occurs in 60% of patients upon abrupt cessation of SSRI drug intake, thought to be due to relative deficiency of serotonin
Onset is within a few days of cessation, usually lasting for 3-4 weeks
Includes 5 core somatic symptom sets:
1. Disequilibria
2. Gastrointestinal symptoms
3. Flu-like symptoms
4. Sensory disturbances
5. Sleep disturbances
What are serotonin norepinephrine reuptake inhibitors (SNRIs) (venlafaxine, duloxetine)?
First-line drugs for the treatment of depression that block the reuptake of both serotonin and norepinephrine (called dual-action antidepressants). May have modestly improved efficacy compared with SSRIs
2 types:
1. Venlafaxine (Effexor)
2. Duloxetine (Cymbalta)
Very similar onset as SSRIs; NT levels increase quickly, but SNRIs have a 4-6 week onset of action
How do the side effects and risk of SNRIs (venlafaxine, duloxetine) compare to those of other antidepressants?
Both side effects and risk of overdose with SNRIs is worse than SSRIs but better than TCAs and MAOIs
What is bupropion (Welbutrin) (mechanism, side effects)?
Bupropion (Welbutrin) is the only norepinephrine-dopamine reuptake inhibitor; it is a first-line drug for the treatment of depression that blocks the reuptake of both norepinephrine and dopamine (called dual-action antidepressants). This mechanism is similar to cocaine but it is not generally abused. It is also used for nicotine addiction, as it antagonizes certain nicotinic receptors.
Dopamine potentiation effects can also treat children with ADHD.
Side effects: it does not affect serotonin reuptake so it does not have the side effects of SSRIs, but…
- Produces effects of minimal sexual dysfunction or enhanced sexual functioning
- May result in weight loss
- General side effects include anxiety, restlessness, tremor, and insomnia
- Serious side effects include psychosis and seizures
What are first-generation antidepressants (TCAs, MAOIs)?
These agents, tricyclic antidepressants (TCAs) and monoamine oxidase inhibitors (MAOIs) were introduced in the 1950s and 1960s to treat depression; both drug classes increase the levels of norepinephrine and serotonin in the brain
How do tricyclic antidepressants (TCAs) compare to SSRIs?
TCAs were created in the 1950s and 1960s, but newer drugs like SSRIs are no more effective
TCAs are cheaper but produce more undesirable side effects
What is different among the varying types of tricyclic antidepressants (TCAs)?
TCAs are named based on chemical structure, and all look and function similarly but vary in side groups
What is the mechanism of action of tricyclic antidepressants (TCAs)?
- Inhibit presynaptic norepinephrine and serotonin reuptake transporters
- Inhibit postsynaptic histamine, acetylcholine, and several other receptors
4 side effects of tricyclic antidepressants (TCAs)
- Anticholinergic activity can lead to confusion, memory and cognitive impairment, dry mouth, blurred vision, increased heart rate, and urinary retention
- Antihistaminic activity can cause drowsiness and sedation
- Antiadrenergic effects can cause postural hypotension
- Life-threatening effects are concerning, especially for overdose in a suicidal patient population:
- Cardiac effects like arrythmias
- Excitement and convulsions
- Respiratory depression and coma
What is the mechanism of action of monoamine oxidase inhibitors (MAOIs)?
MAOIs inhibit monoamine oxidases such as MAO-A, which metabolizes dopamine, norepinephrine, and serotonin; they also inhibit tyramine metabolism, leading to further increases in norepinephrine
What is phenelzine (Nardil)?
First-generation antidepressant, monoamine oxidase inhibitor (MAOI) that is used as a treatment of depression by inhibiting monoamine oxidases, thereby inhibiting metabolism of dopamine, norepinephrine, and serotonin; also inhibits tyramine metabolism, leading to further increases in norepinephrine
What is imipramine (Tofrenil) (mechanism)?
First generation antidepressant, tricyclic antidepressant (TCA) that is used as a treatment of depression by:
1. Inhibiting presynaptic norepinephrine and serotonin reuptake transporters
2. Inhibiting postsynaptic histamine, acetylcholine, and several other receptors
What is the relationship between tyramine and monoamine oxidase inhibitors (MAOIs)?
MAOIs inhibit tyramine metabolism; tyramine increases blood pressure, leading to potential interactions:
- Eating a high tyramine food like cheese while taking a MAOI can easily raise systolic blood pressure
- In extreme cases, ingesting tyramine-containing foods while taking MAOIs can cause an “adrenergic storm,” causing extreme tachycardia, extreme hypertension, and possibly death
What is trazodone (Desyrel) (mechanism of action, effectiveness, side effects)?
Trazodone (Desyrel) is a second generation antidepressant
Mechanism: Blocks 5-HT2 receptors and has a metabolite m-chlorophenylpiperazine that is a serotonin agonist
Trazodone is therapeutically as efficacious as TCAs
Side effects:
- Drowsiness most common
- Priapism is rare but serious effect, requiring surgery in about 33% of cases and can cause permanent impotence
- Modest effects on cognitive functioning even with overdoses
What is the goal of acute treatment of major depressive disorder (MDD)?
Remission of all symptoms
Are antidepressants intended for acute or long-term treatment?
Most antidepressants are approved for both acute and long-term treatment of major depression
What is the success rate of antidepressants?
Antidepressants achieve remission in about 30-40% of patients within a single trial of 8-12 weeks
There is improved response with sequenced augmentation or switching drugs in cases with inadequate response therapy; switching + augmentation leads to 70-80% of patients being able to achieve remission
Once an adequate response in achieved, therapy is continued for a minimum of 6-12 months
What is the recurrence rate of depression?
In patients who have a single episode of major depressive disorder (MDD), about 85% will have at least one recurrence, and many patients will have multiple recurrences
There is significant protective benefit when antidepressants are continued long-term for patients with recurrent MDD
What is esketamine (Spravato)?
Nasal spray with in-clinic adminisatration that was FDA approved in 2019 to treat depression (ketamine nasal spray); it can cause depression relief within hours and is intended for patients resistant to other treatments
2 general effects of psychostimulants (CNS stimulants)
- Augment monoamine neurotransmitter action (particularly dopamine, but also serotonin and norepinephrine)
- Increase dopaminergic activity in the brain’s central reward pathway (behavioral reinforcement, abuse, dependency, and craving)
5 main CNS stimulants
- Cocaine
- Amphetamines
- Methylphenidate
- Ephedrine and cathinone
- Synthetic cathiones (i.e., bath salts)
What is the history of cocaine?
- About 5,000 years ago: thought that leaves of coca plant were first used
- 1855-1860: cocaine identified and purified
- Mid-to-late 1800s: cocaine identified as local anesthetic, combined with wine, in Coca Cola, and other commercial products
- Sigmund Freud once recommended cocaine
- 1914 Harrison Narcotic Tax Act: cocaine baned in patent medicines and beverages
- 1918: procaine (novocaine) developed as synthetic local anesthetic
What is the mechanism of action of cocaine?
Blocks dopamine reuptake transporters (and other monoamine transporters) leading to an accumulation of dopamine in the synaptic cleft
3 acute neurotransmitter and biological effects of cocaine (and long-term effects)
Has actions in both the central and peripheral nervous systems:
1. Activates a “fight or flight” response due to increased norepinephrine (e.g., vasoconstriction)
2. Increased central arousal and a sense of energy; anorexia, hyperthermia
3. “Euphoria” (tolerance) and rewarding properties; dependency due to increased dopamine in reward pathway
After acute effects wear off: depression, dysphoria, sleepiness, craving
What is the dopaminergic central reward pathway?
Dopaminergic pathway involving neurons projecting from the ventral tegmental area (VTA) to the nucleus accumbens (NA) and prefrontal cortex (PFC) that is likely involved in sensing/processing reward; activated by drugs of abuse
What is the relationship between cocaine and sodium channels?
Cocaine is also a sodium channel blocker, and for this purpose can be used topically for ENT procedures, where vasoconstrictor activities can also reduce bleeding; possibly contributes to cardiac toxicity via this mechanism
Generally, this action is not thought to contribute to rewarding or addictive properties
3 forms of cocaine
- Coca leaves: chewed by native South Americans
- Cocaine salt as powder (cocaine hydrochloride, “snow”):
- Water-soluble
- May be administered orally, intravenously, or nasally
- Cannot be smoked - Cocaine in the base (crystal) form (crack; freebase):
- Insoluble in water but soluble in alcohol, acetone, or ether
- Heating the freebase converts cocaine to a stable vapor that may be inhaled
Why is smoking cocaine (crack, freebase form) especially concerning?
Cocaine in the base (crystal) form can be heated and inhaled, and smoking it has rapid onset of action; per the NIDA, this increases likelihood of misuse
Describe the distribution of cocaine (pharmacokinetics)
Penetrates brain readily; initial brain concentrations exceed plasma concentrations, but then it redistributes to other tissues
Crosses placenta (it and metabolites are also stored in uterine wall/placental membrane)
Describe the metabolism of cocaine (pharmacokinetics)
Half life in plasma is about 50 minutes, but it remains in the brain for 8+ hours
Metabolized by enzymes in plasma and liver; the major metabolite is benzoylecgonine, which is also used to test for cocaine use
What is benzoylecgonine?
Present in the plasma and liver, the major metabolite of cocaine; it is also used to test for cocaine use
What happens when cocaine and ethanol are co-used?
Creates cocaethylene, which is pharmacologically as active as cocaine, potentiating the euphoric effect and increasing the risk of dual dependency and the severity of withdrawal with chronic use
Cocaethylene is more toxic and the metabolite exacerbates cocaine toxicity
Cocaethylene has a half-life of 150 minutes
What are the pharmacological side effects of cocaine?
With long-term, high-dose use, cocaine can cause hallucinations and behavioral effects (impulsive or compulsive behavior and aggressive, homicidal behaviors)
6 mid-1900s clinical uses of amphetamines
- Schizophrenia
- Morphine addiction
- Tobacco smoking
- Severe hiccups
- Appetite suppression
- WWII pilot endurance
Abuse became a problem
3 current clinical uses of amphetamines
- ADHD
- Narcolepsy/IH
- Binge eating disorder (one FDA-approved drug)
3 forms of amphetamines
- Amphetamine pills/powder: can be taken orally or snorted nasally
- Amphetamine salts: can be dissolved and taken intravenously
- Methamphetamine in the freebase form (ice, crystal meth): can be smoked
What is the mechanism of action of amphetamines?
- Enter dopamine transporters (DAT) in the presynaptic neuron, preventing dopamine reuptake
- Interferes with the actions of the vesicular monoamine transporter (VMAT) within the cell, preventing the storage/packaging of dopamine and elevating intracellular levels; this causes the DAT to act in reverse, pumping cells into the synaptic cleft instead of reuptaking dopamine
Both of these actions lead to dopamine accumulation
Note: this can occur with other monoamines as well, similar to the actions of cocaine
Additional mechanims likely contribute to its ability to increase synaptic dopamine (and other monoamines)
Do amphetamines cross the placenta?
Yes, amphetamines cross the placenta
How long do amphetamines remain in the body?
The half-life of amphetamine is measured “in hours”
Methamphetamine has a half-life of about 11 hours
What is thought to be the pathophysiology of ADHD?
Thought that dysregulation of dopamine and norepinephrine in certain brain regions contributes to ADHD
How do CNS stimulants relate to ADHD?
Formulations of methylphenidate and amphetamine are considered first-line treatments for ADHD; they can improve symptoms but have some controversy and some potential issues with use
Note that non-stimulant drugs can also be used to treat ADHD
What is methylphenidate (mechanism, onset, half-life)?
CNS stimulant that is considered a first-line treatment for ADHD
Mechanism: Inhibits postsynaptic dopamine (and noreepinephrine) reuptake transporters, like cocaine; has other actions as well
Onset/half-life: Original dose form (Ritalin) has peak levels in blood about 2 hours after oral administration (it is slowly taken up into the brain after oral delivery); half-life is about 2-3 hours
Because of relatively short action, different dosage forms with slow release and even pro-drug forms were developed
What are amphetamine (Adderall) and lisdexamfetamine (Vyvanse)?
CNS stimulants that are first-line drugs for the treatment of ADHD
Lisdexamfetamine (Vyvanse) contains the amphetamine molecule coupled to lysine and may have less abuse potential; it is also approved for binge eating disroder
What are the side effects of CNS stimulants (psychostimulants) for ADHD?
- Appetite reduction, possible growth suppression
- Night-time insomnia
- BP, heart rate increases (concerns for patients with cardiac issues)
- Psychiatric problems
3 reasons ADHD drugs (CNS stimulants) are abused, and 3 possible issues with this abuse
Abused for:
1. Study aids
2. Weight loss
3. High (euphoria)
Possible issues:
1. Side effects from “reformulation”
2. Side effects from stimulants themselves
3. Legal implications (schedule II drugs)
When were antipsychotics first created?
Effective antipsychotics weren’t created until about 1950
What are first generation antipsychotics (FGA),and what are 2 common examples?
“Typical,” “conventional,” neuroleptic, “older drugs” that induce antipsychotic effects through D2 antagonism; specifically, binding affinity to D2 receptors is very strongly correlated with antipsychotic potency (positive symptom amelioration) and a high risk of side effects due to D2 blockade
Less commonly used than SGAs, and have a higher risk of side effects from D2 antagonism
2 common examples:
1. Haloperidol (Haldol)
2. Chlorpromazine (Thorazine)
What are second generation antipsychotics (SGA)?
“Atypical” antipsychotics or “newer drugs” that are typically characterized by 5-HT2A antagonism and D2 antagonism or partial antagonism; SGAs as a group have higher affinity for 5-HT2A receptors than D2 receptors
More commonly used than FGAs, and there is generally a lower risk of causing side effects via D2 antagonism
Treat positive symptom clusters, and although controversial, might have some impact on negative symptoms (or at least not make them worse)
What is psychosis?
Condition characterized by loss of contact with reality; can have multiple causes
What is schizophrenia, and how are its symptoms classified?
Complex mental illness with psychotic and other symptoms
Symptoms can be:
- Positive: excess or distortion of normal function
- Negative: decrease or loss of normal function
- Cognitive: defects in memory and attention
Positive symptom clusters are thought to be the most responsive to antipsychotic drugs
Medications can help, but there is a high rate of medication non-compliance/discontinuance, and some patients have refractory disease
How prevalent is schizophrenia?
Most common psychotic disorder, about 0.3% of the population
Peak incidence is at 15-24 years
Is schizophrenia genetic?
Schizophrenia can have a genetic basis:
- 10% of people who have a first-degree relative with the disorder will develop schizophrenia
- Having a second-degree relative with the disease also increases risk
- If someone has an identical twin with schizophrenia, they have about a 50% chance of also developing the disease
However, it is not purely genetic; complex trait and genetic/environmental interactions possibly contribute to neurodegeneration or dysfunction
What is the dopamine hypothesis of schizophrenia?
The dopamine hypothesis posits that “out of tune” dopaminergic activity (primarily in parts of the striatum and cortex) likely contributes to schizophrenia
This is the earliest concept for the pathophysiology of schizophrenia, and it is important for understanding schizophrenia symptoms, but it does not explain everything
This is why many antipsychotics act at D2 receptors, for drugs that increase dopaminergic activity aggravate/produce psychosis
Where do schizophrenia symptom clusters manifest in the brain?
Positive symptoms:
- Striatum
- Nucleus accumbens
Negative/cognitive symptoms:
- Frontal cortex (DLPFC, VMFC)
What are functions of dopamine/D2 receptors in different parts of the brain (pituitary, striatum, nucleus accumbens)?
Pituitary: limits prolactin release
Part of striatum: regulate movement/motor control (extra pyramidal nervous system)
Nucleus accumbens: reward
Also involved in receiving/processing some emetic (vomiting) signals
What is the serotonin hypothesis of schizophrenia (and 3 underlying reasons for this hypothesis)?
The serotonin hypothesis of schizophrenia suggests that dysregulation of serotonergic systems contributes to the pathophysiology of depression
This originated because:
1. Serotonin (5-HT) receptor agonists, like LSD, produce schizophrenic-like symptoms
2. Atypical antipsychotics (SGAs) have greater affinity for 5-HT2A than D2
3. 5-HT can modulate dopamine signaling
What is the glutamate hypothesis of schizophrenia, and what is one reason for and against this hypothesis?
The glutamate hypothesis of schizophrenia posits that dysfunction in glutamergic signal transduction contributes to the pathophysiology of schizophrenia
A reason for this hypothesis is that phencyclidine (PCP) and ketamine are NMDA antagonists and can heavily mimic the effects of schizophrenia; they also exacerbate psychosis and cognitive symptoms of schizophrenia
However, so far, drugs directly modulating glutamate receptors have failed in clinical trials
What is the acetylcholine hypothesis of schizophrenia (and 3 supports for this hypothesis)?
The acetylcholine hypothesis of schizophrenia suggests that dysfunction in acetylcholine signaling contributes to the pathophysiology of schizophrenia
This has some support because:
1. M4 acetylcholine receptor “knockout mice” had schizophrenia-like behaviors
2. An M4 agonist had efficacy in a phase II clinical trial
3. Clozapine (Clorazil) is a second generation antipsychotic (SGA) that has M4 agonist activities
On what receptors do antipsychotics typically act?
Varies from drug to drug, but all act at D2 receptors; many antipsychotics actually impact several neurotransmitter receptors
What are haloperidol (Haldol) and chlorpromazine (Thorazine), and how do they compare?
First generation antipsychotics (FGAs), AKA typical antipsychotics, that induce antipsychotic effects via D2 receptor antagonism; specifically, D2 receptor antagonism in parts of the striatum is highly correlated to the amelioration of positive cluster symptoms
Haloperidol (Haldol):
- Strong D2 antagonistic activity (high potency)
- Most commonly used FGA
- Higher risk for side effects due to D2 antagonism
Chlorpromazine (Thorazine)
- Not as strong a D2 antagonist as haloperidol (low potency)
- Has actions at other neurotransmitter receptors and can cause side effects due to actions at these other receptors (weight gain, sedation, orthostasis, anti-cholinergic effects)
What are the respective effects of D2 antagonism in the striatum and cortex of those with psychosis?
Striatum: though that dopaminergic activity is too high in psychosis, causing positive symptoms; benefit of reducing D2 activity via D2 antagonism is amelioration of these positive symptoms
Cortex: thought that dopaminergic activity is too low in psychosis, causing cognitive and negative symptoms; it is possible that reducing dopaminergic activity via D2 antagonism has no effect or exacerbates these symptom clusters
5 extrapyramidal side effects (EPSE) associated with D2 antagonism in parts of the striatum
D2 antagonism in parts of the striatum can induce extrapyramidal side effects (EPSE), which can manifest as:
1. Acute dystonia (true EPS)
2. Parkinsonism (true EPS)
3. Akathasia (possible EPS, unclear cause)
4. Tardive dyskinesia (true EPS)
5. Neuroleptic malignant syndrome (possible severe EPS)
What is akathisia, and how does it relate to antispychotic drugs?
D2 antagonism in parts of the striatum can lead to extrapyramidal side effects (EPSE), including the manifestation of akathisia; this is a possible EPS, as the cause is not clear
Akathisia is the most common movement disorder and is characterized by feeling of motor “restlessness”
Rates are thought to be higher with first generation antipsychotic (FGA) drugs than with SGA drugs
What is neuroleptic malignant syndrome, and how does it relate to antipsychotic drugs?
D2 antagonism in parts of the striatum can lead to extrapyramidal side effects (EPSE), including the manifestation of neuroleptic malignant syndrome; possibly an extreme EPS
Neuroleptic malignant syndrome is rare but life-threatening and is often identified early in treatment, though it can be seen after years; severe cases can last for a week after discontinuance
It is characterized by fever, rigidity, mental status changes, and autonomic instability
What is tardive dyskinesia (TD), and how does it relate to antipsychotic drugs?
Tardive dyskinesia (TD) is caused by receptor upregulation in the nigrostriatal tract, leading to involuntary hyperkinetic movements
D2 antagonism in parts of the striatum can lead to extrapyramidal side effects (EPSE), including the manifestation of TD, but only with long-term D2 blockade (late occurring)
The risk of antipsychotics causing this EPSE mirrors that of acute dystonias/Parkinson’s-like effects
What is acute dystonia, and how does it relate to antipsychotic drugs?
D2 antagonism in parts of the striatum can lead to extrapyramidal side effects (EPSE), including the manifestation of acute dystonias
Acute dystonia is a movement disorder caused by D2 antagonism in the nigrostriatal tract, so it is a true EPS
It is characterized by muscle spasms and abnormal postures
What are Parkinson’s-like effects, and how do they relate to antipsychotic drugs?
D2 antagonism in parts of the striatum can lead to extrapyramidal side effects (EPSE), including the manifestation of Parkinson’s-like effects
A Parkinsonism reaction is caused by D2 antagonism in the nigrostriatal tract, so it is a true EPS
It is characterized by slow movement, rigidity, variable tremor, masked facies, and shuffling gait
What is hyperprolactinemia, and how does it relate to antipsychotic drugs?
Hyperprolactinemia is marked by abnormally high levels of prolactin, and is caused by lack of dopamine/D2 action in the pituitary; normally, dopamine/D2 limit prolactin release by the pituitary
In women, this condition causes amenorrhea-galactorrhea and sexual side effects
In men, this condition causes sexual side effects and gynecomastia
D2 antagonism correlates with hyperprolactinemia risk (FGA), but most SGA drugs have low risk of hyperprolactinemia
What are the effects of antipsychotic action in the nucleus accumbens?
The nucleus accumbens is part of the central reward pathway, and D2 blockade in the central reward pathway may lead to “secondary” negative cluster symptoms
How do antipsychotic drugs relate to emesis?
D2 antagonism as caused by antipsychotic drugs has anti-emetic (anti-vomiting) effects in the chemo-receptor trigger zone
Other neurotransmitter receptors involved in emesis are also targeted by some antipsychotics (including SGA drugs)
3 most commonly prescribed second generation antipsychotic (SGA) drugs
- Risperidone (Risperdal) and paliperidone (Invega)
- Clozapine (Clozaril)
- Aripiprazole (Abilify): D2 partial agonist
What are risperidone (Risperdal) and paliperidone (Invega)?
Second generation antipsychotic (SGA) drugs; risperidone is rapidly metabolized to 9-hydroxyrisperidone by CYP-2D6 (except in about 10% of patients), and 9-hydroxyrisperidone is paliperidone (Invega)
Both act as an antagonist at both 5-HT2A and D2 receptors
The two drugs have similar clinical responses and side effects, but there is a higher risk than other SGAs for EPS/TD/hyperprolactinemia, especially at higher doses
May also cause orthostastis
What is clozapine (Clozaril), what are its side effects, and why is it still used?
Clozapine (Clozaril) is a commonly prescribed second generation antipsychotic (SGA) drug that acts as an antagonist at both 5-HT2A and D2 receptors
It has lots of side effects due to actions at multiple neurotransmitter receptors, including:
- Anti-cholinergic effects (constipation), orthostasis, sedation
- Weight gain and other metabolic issues (including dyslipidemia, impaired glycemic control)
- Agranulocytosis (rare but fatal)
- Seizure risk
- Myocarditis
- Sialorrhea
Despite these concerns, it is still used due to:
- People refractory to other drugs
- Suicide risk reduction in those with schizophrenia