Pharma 6: Antidepressant And Antipsychotic Drugs Flashcards
Selective Serotonin Reuptake Inhibitors
Fluoxetine Citalopram
Fluoxetine Citalopram Selectivity to serotonin transporter
300-3000 greater for serotonin than noradrenaline
Fluoxetine, citalopram Adverse effects
Safer than TCAs and MAOI so they’ve replaced them
Fluoxetine, citalopram Therapeutic uses
-Very effective in treating “moderate” depression - Less effective than TCAs in treating severe depression -Treats bulimia nervosa, OCD, anorexia nervosa, panic disorder.
Pharmacokinetics of Fluoxetine, Citalopram
- Absorbed orally - Fluoxetin—>potent inhibitor of CYP2D6 (metabolized TCAs, antipsychotics, antiarrythmatics, B antagonists) - If pt has hepatic impairment—> reduce dose of SSRI
Fluoxetine, Citalopram Adverse effect
-nausea -anxiety -insomnia -anorexia -weight loss -tremors -sexual dysfunction
Antidepressants and <18 years
CAUTION! Possibly causes excitement, insomnia aggression in first few weeks Possibly increased suicidal ideation Lower seizure thresholds
Serotonin syndrome Caused by: S/S:
All SSRI can potentially cause this especially when used with MAOI Characterized by: tremor, hyperthermia, CV collapse—>death
Discontinuation syndrome Caused by S/S
Potentially caused by SSRI after their abrupt withdrawal ((Fluoxetine—>lowest risk due its longer T1/2 and active metabolite)) S/S: headache, malaise, flu like, agitation, irritability, nervousness, sleep difficulties
Venlafaxine, Duloxetine (SNRI) MOA
-Inhibit serotonin and noradrenaline reuptake -Little activity at a-adrenergic, muscuranic, histamine receptor—> less of the side effects resulting from these receeptors
Venlafaxine Pharmacokinetics
Minimal inhibition or CYP450 Substrate for CYP2D6
VENLAFAXINE Side effects
-Nausea -Headache -Sexual Dysfunction -Disziness -Insomnia -Sedation -Constipation High dose—> HTN, TACHYCARDIA
Duloxetine Metabolism
Highly metabolized in liver—> inactive metabolites !Avoid in pt with liver dysfunction
Duloxetine side effects
Gi (common); nausea, dry mouth, constipation Others: insomnia, dizziness, somnolence, sweating, sexual dysfunction. May increase bp and hr
Duloxetine drug-drug interaction
Moderate inhibitor of CYPD26–> increase conc of drugs (antipsychotics) metabolized by it
Tricyclic antidepressants
Imipramine
Imipramine MOA
TCA Therapeutic —>Inhibit serotonin and noradrenaline reuptake +block serotonergic, a adrenergic, histaminic, muscarinic receptors—> adverse effects?
Imipramine Therapeutic uses
Moderate-severe depression Some anxiety disorders eg anxiety attacks
Imipramine Pharmacokinetics
Well absorbed orally Metabolized by hepatic microsomal system—> sensitive to agents that induce/inhibit CYP450?
Imipramine Adverse effects
Antimuscarinic: blurred vision, dry mouth, urinary retention and constipation A adrenergic block: Orthostatic hypotension, dizziness, reflex tachy CV: arrhythmia and SD Sedation: in first few weeks of use Weight gain
Imipramine Precautions
If bipolar pt—> antidepressants may cause a switch to manic behavior Suicidal pt—> LIMITED QUANTITIES OF TCA cuz low TI there4 lethal imipramine dose is 5-6 maximal dose.
TCA Interaction with MAOI
Mutual enhancements—> htn, hyperpyrexia, convulsions, coma
TCA Interaction with direct acting adrenergic drugs
Potentiate effects of biogenic amine drugs by preventing their removal from synaptic cleft
TCA Interaction with ethanol and cns depressants
Toxic sedation
TCA Interaction with indirect acting adrenergic drugs
Block effects of indirect acting sympathomimetic drugs by preventing the drugs from reaching their intracellular sites or action
MAOI
Phenelzine
Phenelzine MOA
Inactivate reversibly/irreversibly MAO—> accumulation of serotonin, NA and dopamine in synaptic cleft
Function of MAO
Inactivates monoamines like norepinephrine, serotonin and dopamine from synaptic vesicle
Phenelzine Consequences of inhibiting MAO
Inhibits MAO in the liver and gut that catalyze oxidative deamination of drugs and toxic substances like tyramine → increase in concentration of tyramine and other drug-drug or food-drug interactions
Phenelzine
Therapeutic uses
- used in patients who are depressed and are unresponsive or allergic to TCA and SSRI or patients with strong anxiety
- Patients with atypical depression
- LAST LINE because of risk of drug driug and drug food interractions.
Phenelzine
Pharmacokinetics
Well abosorbed orally
Metabolized in liver
Excreted rapidly in urine
Phenelzine
Adverse effects
- Drowsiness
- orthostatic hypotension
- blurred vision
- dry mouth
- dysuria
- constipatiopn
- tremors
- OD→Convulsions
Phenelzine when used with other anti-depressants (SSRI) causes
SEROTONIN SYNDROME
Significance of tyramine
- found in aged cheese and meats, chicken liver red wine smoked fish etc
- inactivated by MAO in gut
- tyramine causes release of large quantities of CATECHOLAMINES from stores in nerve terminals→HYPERTENSIVE CRISIS
ie. occipital headache, stiff neck, tachycardia, nausea, hypertension, arrhthmias, seizures, stroke??
Atypical Antidepressant
MIRTAZAPINE
Mirtazapine
MOA
- Antagonizes presynaptic a2-adrenoreceptors→ enhances serotonin and noradrenaline NT
- May also antagonize 5-HT2 receptors…antidepression
- Potent antihistamine effect →sedating useful for depressed pt with difficulty sleeping
- NO ANTIMUSCURANIC (vs TCA)
- NO SECUAL DYSFUNCTION (vs SSRI)
+increase apetie→weight gain
Schizophrenia
Pathophysiology
possibly dysfunction of the mesolimbic or mesocortical dopaminergic neuronal pathways
Dopamine hypothesis of schizophrenia
- ANTIpsychotic properties are explained by post synaptic dopamine antagonism
- Drug induced psychosis is a high risk with drugs that incerease dopamine availability like cocaine, amphetamines, L dopa
- Potential complication of PD pt on L dopa
Limitations of Dopamine Theory
- doesn’t explain cognitive deficits
- D-lysergic acid, 5-HT2A agonist also produces psychotic symptoms ie not just dopamine
First Generation Antipsychotics
Chlorpromazine
Thioridazine
Haloperidol
FGA
MOA
- Block D2 dopamine receptors→ lower dopaminergic NTion in the four dopamine pathways→ antipsychotic effects
- Competetive antagonist of H1, M1, a1 adrenoreceptors
FGA and extrapyramidal symptoms
Particulary HALOPERIDOl→bind tighlty to dopaminergic neuroreceoptors
Less likely with CHLORPROMAZINE→bind weakly
SGA drugs
Aripiprazole
Clozapine
Olanzapine
Second generation antipsychotics
MOA
“atypical antipsychotics”
Antagonize dopamine, srotonin and other receptors
SGAs and extrapyramidal symptoms
Lower incidence of EPS than FGA→FIRST LINE
SGAs are associated with..
Metabolic side effects:
- diabetes
- hyperchol
- weight gain
Antipsychotic effects (on positive symptoms)
All antipsychotics can reduce hallucinations and delusions associated with schizophrenia
ie they reudce the postive symptoms by blocking D2R in the mesolimbic system
!NOTE: Blocking D2R in the nigrostriate pathway—> EPS—> dystonias, parkinson like symptoms, akathisia and tardige dyskinesia. Less so in SGA
Negative symptoms of schizophrenia are mostly responsive to
SGA eg Clozapine
Antiemetic effect of antipsychotics
All antipsychotics have antiemetic effect due to blocking D2R of the chemoreceptor trigger zone
!EXCEPT aripiprazole
Anitcholonergic effects of antipsychotics
CHLOROPROMAZINE, CLOZAPINE, OLANZAPINE
produce anticholinergic effects like blurred vision, confusioj and inhibiiot of Gi and ut
!anticholinergic effect—> decrease risk of EPS
Other effects of antipsychoyics
- Block a adrenergic receptors—> orthostatic hypotension and lightheadedness
- alter temperature regulating mechanisms—>poikilothermia
- block D2R in pituitary—>hyperprolactin
- potent antagonists of H1 histamine receptors chlorpromazine, olanzapine, clozapine—> sedation
- some cause sexual dysfunction
Statistics on the adverse effects of antipsychotics
Can occur in virtually all patients and can be significant in 80% of cases
Adverse effect—> EPS
Extrapyramidal motor effects
due to disturbance in balance between dopaminergic and cholinergic system
- HIGH RISK* haloperidol, fluphenazine—> preferentially block D2R
- LOW RISK* THIORIDAZIN—> strong anticholinergic activity
Adverse effect—> tardive dyskinesia
- Due to long term treatment
- giving up antipsychotics may reduce symptoms
- may be permanent
Neuroleptic malignant syndrome
- Potentially fatal
- reaction to antipsychotics
- must discontinue
Other adverse effects of antipsychotics
- drowsines
- confusion
- dry mouth
- urinary retention
- constipation
- loss of visual accomodation
- hypotension
- orthostatic hypotension
- impaired thermoregulation
- amennorrhea
- galctorrhea
- gynecomastia
- infertility
- ed
- weight gain
- exacerbate DM hyperlipidemia
- QT prologation thioridazine
Cautions and contraindications of antipsychotics
- lower seizure threshold
- elderly pt with dementia related psychosis→ increased risk of mortality
- pt ith mood disorders→monitored for worsening of symptoms and suicidal ideation or behaviors