Antidepressants

Question 1

An 18-year-old woman attends the emergency department with drowsiness. She was found lying in the street. Shortly after admission, she has a tonic clinic seizure which is terminated with lorazepam. On examination, you note mydriasis and urinary retention. Her Glasgow Coma Score (GCS) is currently 11 (M5, V3, E3).

An ECG performed in the department is as follows:

ECG Sinus tachycardia (120 beats per minute); QRS duration 140ms; Dominant terminal R wave in aVR; First-degree AV block

What is the most likely cause?

A. Digoxin

B. Dosulepin

C. Ivabradine

D. Quinine

E. Sertraline

Answer 1

B. Dosulepin is correct, The clinical (e.g. seizures, mydriasis, urinary retention) and electrocardiographic features are most in keeping with tricyclic overdose. These agents block sodium channels resulting in CNS and cardiovascular toxicity in overdose in the form of seizures and ventricular dysrhythmias. Tricyclics mediate their cardiotoxic effects via blockade of myocardial fast sodium channels (e.g. QRS prolongation, tall R wave in aVR), inhibition of potassium channels (e.g. QTc prolongation), and direct myocardial depression.

Digoxin is incorrect, The classical digoxin toxic dysrhythmia combines:
Supraventricular tachycardia (due to increased automaticity)
Slow ventricular response (due to decreased AV conduction)
The broad complex tachycardia in this case makes digoxin toxicity less likely. However rarely this can occur in digoxin toxicity due to a bidirectional ventricular tachycardia (VT) with a frontal-plane axis that alternates by 180 degrees with each successive beat.

Ivabradine (for heart failure) is incorrect. Ivabradine toxicity can cause bradycardia, sinus arrest, and heart block.

Quinine is incorrect. Although quinine is also a sodium channel-blocking agent and can cause a wide complex tachyarrhythmia, the presence of mydriasis and urinary retention favours a diagnosis of amitriptyline toxicity.

Sertraline is incorrect. SSRI overdose can predispose to prolonged QTc and Torsades de pointes. Although seizures and mydriasis (e.g. serotonin syndrome) can occur with SSRI toxicity, the electrocardiographic features of a broad complex tachycardia and a dominant terminal R wave in aVR are more consistent with tricyclic toxicity.

Question 2

what class of drug is Dosulepin

Answer 2

tricyclic antidepressant (more sedative)

Question 3

what class of drug is Trazodone*

Answer 3

‘tricyclic-related antidepressant’

Question 4

what are some risk factors of suicide (mnemonic)?

Answer 4

SADPERSONS
S-sex (male)
A-age (young adult/elderly)
D-depression
P-previous attempt (highest risk factor)
E-Ethanol/drug use
R-rational thinking loss (psychoses)
S-sickness (medical illness)
O-organised plan
N-no spouse/other social support
S-stated future intent

Question 5

SSRI side effects (mnemonic)

Answer 5

5Ss:
1. S =Suicidal ideation for 1-2 weeks…
2. S =Stomach (weight gain, N&V, diarrhoea, headaches, dyspepsia) *for 5-10 days…
3. S =Sexual dysfunction
4. S= Sleep (insomnia) for 5-10 days…
5. S= Serotonin syndrome

Others:
-Anxiety and agitation
-QT interval prolongation (especially associated with citalopram)
-Hyponatraemia (especially in elderly)
-Gastric Ulcer (take with PPIs)

Question 6

TCAs side effects: (anticholinergic, mnemonic)

Answer 6

1. Urinary retention
2. Drowsiness
3. Blurred vision
4. Constipation
5. Dry mouth

Question 7

Antidepressant/SSRI discontinuation symptoms (mnemonics):

Answer 7

SSRI discontinuation syndrome :mFINISH mnemonic

(Flu-like symptoms, Insomnia, Nausea, Imbalance, Sensory disturbances, Hyperarousal)

Antidepressant discontinuation symptoms: (FIRM STOP):
o Flu-like symptoms Sweating
o Insomnia Tummy problems (pain, cramps, D&V)
o Restlessness Off balance (ataxia)
o Mood swings Paraesthesia (shocks, tingles, etc.)

Question 8

cautions with TCAs:

Answer 8

-Contraindicated in those with previous heart disease
-Can exacerbate schizophrenia
-May exacerbate long QT syndrome
-Use with caution in pregnancy and breastfeeding
-May alter blood sugar in T1 and T2 diabetes mellitus
-May precipitate urinary retention, so avoid in men with enlarged prostates
-Uses the Cytochrome P450 metabolic pathway, so avoid in those on other CP450 medications or those with liver damage

Question 9

Cautions with SNRIs:

Answer 9

Contraindicated in those with :
1. history of heart disease
2. high blood pressure

Question 10

why are TCAs not 1st line for depression:

Answer 10

they are toxic in overdose eg amitriptyline, dosulepin

Question 11

MAOI examples

Answer 11

isocarboxazid, phenelzine, selegiline, and tranylcypromine

Question 12

why are serotonin & noradrenaline reuptake inhibitors (eg venlafaxine) not recommended as 1st line for depression?

Answer 12

1. risk of hypertension
2. cardiac arrythmias
3. toxicity in overdose

Question 13

A patient with an extensive medical history comes to the GP complaining of erectile dysfunction.

Which of his prescribed drugs is the most likely cause of his symptoms?

A. Thyroxine

B. Sildenafil

C. Citalopram

D. Lithium

E. Amitryptilline

Answer 13

C. Citalopram

Sexual dysfunction is a recognised and common side effect of SSRIs

Not E: Tricyclics do not commonly cause sexual dysfunction. They are strongly associated with anticholinergic activity]

Not D: lithium

Lithium can rarely be associated with erectile dysfunction, but it is a much more commonly seen as a result of SSRIs. Hence, this is not the correct answer