Serotonin and Noradrenaline Re-uptake Inhibitors (SNRIs)

This new class of drug (unrelated to other antidepressants) is used in the management of depression and anxiety.¹ Venlafaxine is the first and only drug available in this class in the UK. Both venlafaxine and its major metabolite, O-desmethylvenlafaxine (ODV), inhibit serotonin and norepinephrine (and to a lesser extent dopamine) reuptake into nerves.

Venlafaxine should generally be used under specialist supervision, this is particularly so in severely depressed or hospitalised patients² who need doses of 300mg daily or more.
It should not be prescribed to children aged under 18,¹ because increased risk of self-harm and suicidal thoughts and little evidence for efficacy in this group.²

Milnacipran and duloxetine are other SNRIs in development.³ They may be better tolerated and not have venlafaxine's cardiovascular toxicity (particularly in overdose).

• Major depression including depression accompanied by anxiety¹
• Generalised anxiety disorder

(see individual drug monographs for full list)

• Uncontrolled hypertension (monitor BP in all patients)²
• Patients at high risk of ventricular arrhythmia - e.g. patients with significant LV dysfunction,¹ heart failure, and patients with ECG rhythm abnormalities
• Severe hepatic or renal impairment, and patients with electrolyte imbalances
• Pregnancy or breast feeding
• Children (aged less than 18)¹
• Not to be used concurrently or within 2 weeks of an MAOIs

• Perform a baseline ECG and check BP to help exclude pre-existing hypertension or heart disease
• Avoid in patients with ECG abnormal - eg showing evidence of IHD or arrhythmia - especially QT abnormal
• Reduce dose in hepatic or renal impairment
• Full therapeutic effect may not be apparent over the first two weeks of treatment
• Watch and monitor mental state carefully as this may deteriorate (agitation)

• Repeat BP check within one month or starting drug or dose change, and check at least 6 monthly thereafter
• Ensure patient is reviewed regularly (particularly if recently starting drug or adjusting dose) e.g. for worsening restlessness, agitation, mania, current suicide risk

It is usual to taper dose slowly over a few weeks to avoid withdrawal symptoms.

• Hypertension - if this develops reduce dose or discontinue and consider starting alternative agent (take advice of specialist)⁴
• Serotonin Syndrome