Venlafaxine

Venlafaxine belongs to the serotonin and noradrenaline reuptake inhibitors (SNRIs). By keeping more of these two messengers available between nerve cells, it helps lift a low mood over a period of weeks rather than days. The UK SmPC lists two uses: treating major depressive episodes and, once the episode has settled, preventing recurrence. Improvement is gradual, and the first few weeks are a period when patients are monitored closely.

Two strengths are available here. With the lower 37.5 mg strength, the smallest pack holds 30 tablets, followed by 60, 90, 120, 180, 240 and 360. The 75 mg strength adds a smaller pack of 10 tablets ahead of the same range from 30 up to 360. These are imported generic tablets; check the pack to see whether they are standard (immediate-release) or prolonged-release, because the two are taken differently.

In the UK, venlafaxine is supplied only on prescription, as a POM. Standard tablets of 37.5 mg and 75 mg are licensed, along with an oral solution and a wide range of prolonged-release capsules and tablets. Among the branded prolonged-release versions are Efexor XL, Vencarm XL, Venaxx XL, Venladex XL and Sunveniz XL. No UK licence covers the imported generic sold here; it is a separate product from the medicines named above.

For standard tablets, the SmPC gives a starting dose of 75 mg a day split into two doses and taken with food, at roughly the same times each day. If the response is inadequate, the dose may be raised in steps no closer than two weeks apart (or, where symptoms are severe, no closer than four days), up to a maximum of 375 mg a day. Each increase follows a clinical review. People with mild or moderate liver problems usually need about half the dose; the same 50% reduction applies to severe kidney impairment and dialysis. Trials in children and teenagers did not show benefit, so it is not advised below the age of 18. Antidepressant treatment normally continues for at least six months after recovery. Someone stable on standard tablets can later be moved to a once-daily prolonged-release product at the nearest equivalent dose, for example 37.5 mg twice daily becoming 75 mg once daily. Older patients need no automatic dose change, but they are kept on the lowest effective dose and watched more closely when it is increased.

Venlafaxine must not be combined with irreversible MAO inhibitors: a 14-day gap is needed after stopping an MAOI and a seven-day gap before starting one. The risk of serotonin syndrome rises when it is taken with triptans, other antidepressants, lithium, tramadol and several other opioids, linezolid or St John's Wort. Blood pressure can rise in a dose-related way, so it is checked before starting and reviewed after each increase; heart rate may also go up. Bleeding is more likely alongside anticoagulants or antiplatelet medicines, and low sodium levels can develop, particularly in older people and those on diuretics. Alcohol is best avoided. Thoughts of self-harm, especially early in treatment, need urgent medical attention.

In clinical studies, more than one person in ten noticed feeling sick, a dry mouth, headaches or heavy sweating, often at night. Stopping abruptly can trigger withdrawal reactions such as dizziness, sensory disturbances, sleep problems, anxiety and nausea. The SmPC advises reducing the dose over at least one to two weeks, and some people need a much slower taper lasting months.

The choice of Venlafaxine, its dose and the length of treatment are for the doctor or prescriber to decide.