NERVOUS SYSTEM: ANTIDEPRESSANTS - VENLAFAXINE + MIRTAZAPINE

Question 1

ADs VENLAFAXINE + MIRTAZAPINE: INDICATIONS

Answer 1

• Option for Tx of major depression where SSRIs are ineffective or not tolerated
• GAD (V)

Question 2

ADs VENLAFAXINE + MIRTAZAPINE: MOA

Answer 2

• Venlafaxine = SNRI, interfering with uptake of these NTs in the synaptic cleft
• Mirtazapine = antagonist of inhibitory pre-synaptic a-2 receptors

Both drugs increase availability of monoamines for neurotransmission

• Venlafaxine is a weaker antagonist of muscarinic and histamine (H1) receptors than tricyclic antidepressants
• Mirtazapine is a potent antagonist of histamine (H1) but not muscarinic receptors
• They therefore have fewer antimuscarinic side effects than tricyclic antidepressants, although mirtazapine commonly causes sedation.

Question 3

ADs VENLAFAXINE + MIRTAZAPINE: ADVERSE EFFECTS

Answer 3

• GI UPSET (dry mouth, nausea, change in weight and diarrhoea/constipation)
• CNS effects = (headache, abnormal dreams, insomnia, confusion and convulsions)
• Less common but serious adverse effects include hyponatraemia and serotonin syndrome
• Suicidal thoughts and behaviour may increase.
• Venlafaxine prolongs the QT interval and can increase the risk of ventricular arrhythmias.
• Sudden drug withdrawal can cause gastrointestinal upset, neurological and influenza-like symptoms and sleep disturbance.
• Venlafaxine is associated with a greater risk of withdrawal effects than other antidepressants.

Question 4

ADs VENLAFAXINE + MIRTAZAPINE: WARNINGS

Answer 4

• Elderly
• Hepatic or Renal Impairment
• V used with caution in all CVD patients

Question 5

ADs VENLAFAXINE + MIRTAZAPINE: INTERACTIONS

Answer 5

• Combo with others AD classes, increase risk of adverse effects