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Efexor (venlafaxine)

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Efexor (venlafaxine) (Contd)

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.

Disturbances of the gut such as diarrhoea, constipation, nausea, vomiting or abdominal pain

Dry mouth

Difficulty in sleeping (insomnia)

Sleepiness

Dizziness

Sweating

Nervousness

Weakness or loss of strength (asthenia)

Sexual problems

Headache

Loss of appetite

Weight changes

Pain in the muscles and joints

Abnormal dreams

Agitation and anxiety

Confusion

Pins and needles (paraesthesia)

Tremor

Awareness of your heartbeat (palpitations)

Visual disturbances

Blood disorders

Abnormal heart beats (arrhythmias)

The side effects listed above may not include all of the side effects reported by the drug's manufacturer. For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to ensure that the combination is safe.

This medicine must not be taken at the same time as, or within two weeks of taking a monoamine oxidase inhibitor (MAOI). These include the following:

MAOI antidepressants, eg isocarboxazid, phenelzine, tranylcypromine

the MAO-A inhibitor antidepressant, moclobemide

the MAO-B inhibitors for Parkinson's disease, rasagiline and selegiline

the antibiotic linezolid.

Conversely, an MAOI medicine should not be started until at least one week after stopping venlafaxine. This is because using these medicines together can cause a serious and potentially life-threatening interaction.

If venlafaxine is taken with other medicines that enhance serotonin in the brain, there may be an increased risk of side effects such as agitation, restlessness and diarrhoea, known as the 'serotonin syndrome'. Other medicines that increase serotonin activity include the following:

SSRI antidepressants, eg fluoxetine, paroxetine, sertraline (SSRIs should only be used in combination with venlafaxine under specialist supervision)

lithium

the herbal remedy St John's wort (Hypericum perforatum)

tramadol

tryptophan

triptans for migraine, eg sumatriptan.

Venlafaxine should not be used in combination with sibutramine.

Venlafaxine may increase the blood levels of the following medicines, and this may increase the risk of side effects from these medicines:

clozapine

haloperidol

tricyclic antidepressants such as desipramine.

Venlafaxine may decrease the blood level of the anti-HIV medicine, indinavir. This may possibly decrease the effectiveness of the indinavir, but the clinical importance of the interaction is not yet known.

Cimetidine may increase the blood level of venlafaxine. This is not usually a problem, but if you are elderly or have liver problems you should be monitored more closely by your doctor if you are taking these two medicines together.

The antibiotic erythromycin and the antifungal ketoconazole may also increase the blood level of venlafaxine. These anti-infectives should be avoided where possible in people taking venlafaxine.

Venlafaxine may enhance the anti-blood-clotting effect of anticoagulant medicines, such as warfarin. If you are taking an anticoagulant your blood clotting time (INR) should be monitored when you start or stop taking venlafaxine and after any dose changes.

There may be an increased risk of bleeding if venlafaxine is taken by people who are taking any of the following medicines, which are known to affect the ability of the blood to clot:

anticoagulants such as warfarin

antiplatelet medicines such as aspirin, dipyridamole

non-steroidal anti-inflammatory drugs (NSAIDs) eg ibuprofen, diclofenac.

Other medicines containing the same active ingredient

Efexor XL

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