Tag: Tricyclic Antidepressants

Tricyclic Antidepressants

TRICYCLIC ANTIDEPRESSANTS

Q. 1

All of the following are predictable adverse effects of tricyclic antidepressants, EXCEPT:

 A

Decrease in seizure threshold

 B

Weight gain

 C

Insomnia

 D

Dry mouth

Q. 1

All of the following are predictable adverse effects of tricyclic antidepressants, EXCEPT:

 A

Decrease in seizure threshold

 B

Weight gain

 C

Insomnia

 D

Dry mouth

Ans. C

Explanation:

Tricyclic antidepressants produce sedation rather than arousal.
Use of tricyclics can be therapeutic for insomnias associated with depression.
Other effects include antimuscarinic effects (dry mouth, blurred vision, tachycardia, urinary retention), a-adrenergic effects (orthostatic hypotension), weight gain, and a decrease in seizure threshold, which means that patients are more susceptible to having seizures.
 
Ref: O’Donnell J.M., Shelton R.C. (2011). Chapter 15. Drug Therapy of Depression and Anxiety Disorders. In L.L. Brunton, B.A. Chabner, B.C. Knollmann (Eds),Goodman & Gilman’s The Pharmacological Basis of Therapeutics, 12e.

Q. 2

All of the following is are serotonin-dopamne antagonist except:

 A

Zotepine

 B

Loxapine

 C

Sertindole

 D

All

Q. 2

All of the following is are serotonin-dopamne antagonist except:

 A

Zotepine

 B

Loxapine

 C

Sertindole

 D

All

Ans. B

Explanation:

B  i.e. Loxapine 


Q. 3

Narrow therapeutic index is seen with –

 A

Desipramine

 B

Lithium

 C

Penicillin

 D

a and b

Q. 3

Narrow therapeutic index is seen with –

 A

Desipramine

 B

Lithium

 C

Penicillin

 D

a and b

Ans. D

Explanation:

Ans. is ‘a’ i.e., Desipramine; ‘b’ i.e., Lithium

Drugs with low therapeutic index (High alert drugs)

o Amphotericin B

o Aminoglycosides

o Carbamezapine

o Cyclosporine

o Clindamycin

o Clonidine

o Digoxin

o Disopyrami de

o Dimercapral

o Guanethidine

o Isoetharine

o I soproterenol

o Levothyroxine

 

Lignocaine

o Lithium

o Metaproterenal

o Minoxidil

o Primidone

o Procainamide

o Phenytoin

o Quinidine

o Tricyclic antidepressants

o Theophylline

o  Warfarin

o Valproate

Note : Desipramine is a Tricyclic antidepressant.

Quiz In Between


Q. 4

Cardiac conduction defect seen with Tricyclic antidepressants are due to-

 A

NE & serotonin uptake inhibitor

 B

Antimuscarinic action on heart

 C

Only NE uptake inhibition

 D

Both NE uptake inhibition and antimuscarinic action on heart

Q. 4

Cardiac conduction defect seen with Tricyclic antidepressants are due to-

 A

NE & serotonin uptake inhibitor

 B

Antimuscarinic action on heart

 C

Only NE uptake inhibition

 D

Both NE uptake inhibition and antimuscarinic action on heart

Ans. D

Explanation:

Ans. is ‘d’ i.e., Both NE uptake inhibition and antimuscarinic action on heart

o The commonest cardiovascular effect of tricyclic antidepressant overdose is sinus tachycardia, which is attributable to the inhibition of norepinephrine reuptake and the anticholinergic action.


Q. 5

Which of the following is not a side effect of amitriptyline

 A

Constipation

 B

Fine tremors

 C

Weight loss

 D

Dry mouth

Q. 5

Which of the following is not a side effect of amitriptyline

 A

Constipation

 B

Fine tremors

 C

Weight loss

 D

Dry mouth

Ans. C

Explanation:

Ans. is ‘c’ i.e., Weight loss

TCAs (e.g. amitriptyline) cause weight gain


Q. 6

True about Imipramine is:         

September 2007

 A

Antiepileptic

 B

Antidepressant

 C

Anxiolytic

 D

Antipsychotic

Q. 6

True about Imipramine is:         

September 2007

 A

Antiepileptic

 B

Antidepressant

 C

Anxiolytic

 D

Antipsychotic

Ans. B

Explanation:

Ans. B: Antidepressant

Imipramine is a tricyclic antidepressant with general pharmacological properties similar to amitriptyline and doxepin. It possesses anticholinergic properties which are responsible for certain of its side effects.

The most prominent action of TCA’s is their ability to inhibit norepinephrine transporter and serotonin transporter located at neural/platelet membrane at low and therapeutically attained concentrations.

Quiz In Between


Q. 7

True regarding bupropion is:     

September 2009

 A

Dopamine reuptake stimulator

 B

It is an antianxiety drug

 C

No precipitation of seizures

 D

Nicotinic receptor antagonist

Q. 7

True regarding bupropion is:     

September 2009

 A

Dopamine reuptake stimulator

 B

It is an antianxiety drug

 C

No precipitation of seizures

 D

Nicotinic receptor antagonist

Ans. D

Explanation:

Ans. D: Nicotinic receptor antagonist

Bupropion/amfebutamone is an atypical antidepressant and smoking cessation aid.

It acts as a norepinephrine and dopamine reuptake inhibitor (NDRI), as well as alpha3 beta4-nicotinic receptor antagonist.

Bupropion belongs to the chemical class of aminoketones and is similar in structure to stimulants cathinone and diethylpropion, and to phenethylamines in general.

Bupropion is an effective antidepressant on its own but it is particularly popular as an add-on medication in the cases of incomplete response to the first-line selective serotonin reuptake inhibitor (SSRI) antidepressant.

Since it does not inhibit serotonin reuptake at all (or very insignificantly), bupropion does not cause weight gain or sexual dysfunction like the SSRI group of antidepressants.

It precipitates seizures


Q. 8

The tricyclic antidepressant with LEAST autonomic and cardiotoxic effects:             

March 2004

 A

Amitriptyline

 B

Desipramine

 C

Lofepramine

 D

Protriptyline

Q. 8

The tricyclic antidepressant with LEAST autonomic and cardiotoxic effects:             

March 2004

 A

Amitriptyline

 B

Desipramine

 C

Lofepramine

 D

Protriptyline

Ans. C

Explanation:

Ans. C i.e. Lofepramine


Q. 9

Which of the following is a tricyclic antidepressant‑

 A

Vanalafexine

 B

Fluoxetine

 C

Doxepine

 D

Citalopram

Q. 9

Which of the following is a tricyclic antidepressant‑

 A

Vanalafexine

 B

Fluoxetine

 C

Doxepine

 D

Citalopram

Ans. C

Explanation:

Ans. is ‘c’ i.e., Doxepine 

Quiz In Between



Tricyclic Antidepressants

TRICYCLIC ANTIDEPRESSANTS


TRICYCLIC ANTIDEPRESSANTS

  • Drugs with low safety/therapeutic index (TCA poisoning can occur).

MOA:

  • Acts by inhibiting serotonin & noradrenaline reuptake.
Steps:
  • NA & serotonin initially act on pre-synaptic α2 & 5HT receptors.
  • By inhibiting them, transmitter concentration is increased in synaptic cleft.  
  • Decreased firing of locus ceruleus (NA) & nucleus raphe Magnus (5HT).   

Long-term administration:

  • Results in desensitization of pre-synaptic α2 & 5HT receptors –> Enhanced transmission.
  • Thus, despite immediate inhibition of reuptake process, there is long latency (2-3 weeks) for anti-depressant action of TCA & SSRIs.

Metabolism:

  • Metabolized in liver via demethylation.
  • Results in active metabolite formation.
    • Active metabolites of imipramine – Desipramine.
    • Active metabolites of amitriptyline – Nortriptyline.

Important drugs & characteristics:

  • Bupropion, imipramine, amitriptyline, trimipramine, lofepramine, amoxapine, clomipramine, maprotiline, doxepin, dothiepin etc.,
  • Bupropion MOA: 
    • Inhibits dopamine reuptake
  • Amoxapine MOA:
    • Acts by blocking D2-receptors & also inhibits NA uptake.
    • Metabolite of antipsychotic drug “loxapine”.
    • Risk of extrapyramidal symptoms & convulsion.
  • Imipramine – For nocturnal enuresis in children.
  • (Note: DOC for nocturnal enuresis – desmopressin)
  • Lofepramine -TCA with least cardiotoxic nature.

Actions of TCA’s:

  • Most drugs have powerful anti-cholinergic properties
    • Results in dry mouth, bad taste, blurring of vision, epigastric distress, constipation, urinary hesitancy (especially in males with enlarged prostate) & palpitation.
  • Weak α-blocking property.
  • Lowers seizure threshold (particularly bupropion, clomipramine & maprotiline 
  • Have antipsychotic property (amoxapine)

Adverse effects:

  • Weight gain (except bupropion)
  • Tremors & insomnia
    • Due to inhibition of pre-synaptic NT uptake.
    • Mainly amitriptyline.
  • Cause postural hypotension
    • Due to α1 adrenergic blockade
  • Risk of extrapyramidal symptoms & convulsion – 
    • Mainly Amoxapine.
  • Conduction defects, arrhythmias & hypotension – 
    • Due to inhibition of cardiac fast Na+ channels.
    • Mainly with amitriptyline & dosulepin.
  • Hyperthermia, flushing, mydriasis, paralytic ileus, urinary retention, sinus tachycardia – 
    • Due to inhibition of muscarinic ACh receptors
  • Sedation –
    • Due to H1 histamine receptor inhibition

Overdose manifestations:

  • Are mainly anticholinergic
    • Delirium
    • Urinary retention
    • Blurred vision
    • Constipation
    • Cardiac arrhythmia, at toxic levels.

Exam Important

TRICYCLIC ANTIDEPRESSANTS

  • Tricyclic antidepressants are drugs with low safety/therapeutic index.
  • TCA acts by inhibiting serotonin & noradrenaline reuptake, particularly on
  • On long-term administration of TCA, desensitization of pre-synaptic α2 & 5HT receptors occurs resulting in enhanced transmission.
  • Despite immediate inhibition of reuptake process, there is long latency (2-3 weeks) for anti-depressant action of TCA & SSRIs, mainly due to desensitization of pre-synaptic α2 & 5-HT receptors on long-term administration.
  • Active metabolite of imipramine is desipramine.
  • Active metabolite of amitriptyline is Nortriptyline.
  • Bupropion acts by inhibits dopamine reuptake.
  • Amoxapine acts by blocking D2-receptors & also, inhibits NA uptake.
  • Amoxapine is a metabolite of antipsychotic drug “loxapine”.
  • Imipramine is useful in nocturnal enuresis in children.
  • Most TCA’s have powerful anti-cholinergic characteristics, resulting in dry mouth, bad taste, blurring of vision, epigastric distress, constipation, urinary hesitancy (especially in males with enlarged prostate) & palpitation.
  • Bupropion, clomipramine & maprotiline lowers seizure threshold.
  • Amoxapine has antipsychotic property.
  • TCA with least cardiotoxic property is Lofepramine.
  • Tremors & insomnia are caused by TCA, due to inhibition of pre-synaptic NT uptake.
  • TCA causes postural hypotension, due to  α1 adrenergic blockade.
  • There is risk of extrapyramidal symptoms & convulsion, mainly because of Amoxapine
  • TCA causes conduction amitriptyline defects, arrhythmias & hypotension, due to inhibition of cardiac fast Na+ channels.
  • Among TCA drugs, amitriptyline causes arrhythmia, on toxic dosage.
  • TCA drugs cause hyperthermia, flushing, mydriasis, paralytic ileus, urinary retention, sinus tachycardia, due to inhibition of muscarinic ACh receptors.
  • TCA drugs are sedative in nature, mainly due to H1 histamine receptor inhibition.
  • TCA overdose manifestations are mainly anticholinergic.

 

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