How does it work?

Venlafaxine tablets are a type of antidepressant known as aserotonin and noradrenaline reuptake inhibitor (SNRI).This type of medicine acts on nerve cells in the brain.

In the brain there are numerous different chemical compoundscalled neurotransmitters. These act as chemical messengers between the nervecells. Serotonin and noradrenaline are two such neurotransmitters and havevarious functions that we know of.

When serotonin and noradrenaline are released from nerve cellsin the brain they act to lighten mood. When they are reabsorbed into the nervecells, they no longer have an effect on mood. It is thought that whendepression occurs, there may be a decreased amount of serotonin andnoradrenaline released from nerve cells in the brain.

Venlafaxine works by preventing serotonin and noradrenaline frombeing reabsorbed back into the nerve cells in the brain. This helps prolong themood lightening effect of any released serotonin and noradrenaline. In thisway, venlafaxine helps relieve depression. It is also helpful for relievingdepression that is accompanied by anxiety.

Once you are feeling better, your doctor will usually ask you tocontinue taking this medicine to minimise the chances of your depression comingback, or to prevent you from becoming depressed in the future. The length oftime you take the medicine will vary from person to person, but should be forat least six months after things are back to normal.

It may take between two to four weeks for the benefits of thismedicine to appear, so it is very important that you keep taking it, even if itdoesn't seem to make much difference at first. If you feel your depression hasgot worse, or if you have any distressing thoughts or feelings in these firstfew weeks, then you should talk to your doctor.

What is it used for?

• Depressive illness, including depression associated with anxiety.

Warning!

• Depression is associated with an increased risk of suicidal thoughts, self-harm, and suicide. You should be aware that this medicine may not start to make you feel better for at least two to four weeks. However, it is important that you keep taking it in order for it to work properly and for you to feel better. If you feel your depression or anxiety has got worse, or if you have any distressing thoughts or feelings about suicide or harming yourself in these first few weeks, or indeed at any point during treatment or after stopping treatment, then it is very important to talk to your doctor.
• This medicine may reduce your ability to drive or operate machinery safely. Do not drive or operate machinery until you know how this medicine affects you and you are sure it won't affect your performance.
• It is recommended that you avoid drinking alcohol while taking this medicine.
• You should not suddenly stop taking this medicine, as this can cause withdrawal symptoms such as headaches, tremor, agitation or anxiety, nausea, vomiting, sweating, dizziness, palpitations, diarrhoea, pins and needles or electric shock sensations, emotional instability, difficulty sleeping and abnormal dreams. Withdrawal symptoms are temporary and are not due to addiction or dependence on the medicine. They can usually be avoided by stopping the medicine gradually, usually over a period of weeks or months, depending on your individual situation. Follow the instructions given by your doctor when it is time to stop treatment with this medicine. On rare occasions some people have experienced withdrawal symptoms after accidentally missing a dose of this medicine.
• The use of venlafaxine has been associated with the development of unpleasant or distressing restlessness and the need to move about, often accompanied by an inability to sit or stand still. This is most likely to occur within the first few weeks of treatment. If you experience these symptoms you should consult your doctor.
• This medicine may cause your blood pressure to increase, particularly if you are taking doses higher than 200mg per day. It is recommended that your blood pressure is regularly monitored while you are taking this medicine. If your blood pressure does increase, your doctor may need to reduce your dose of this medicine or stop treatment with it altogether.
• This medicine can occasionally cause your blood pressure to drop when you move from a lying down or sitting position to sitting or standing, especially when you first start taking the medicine. This may make you feel dizzy or unsteady. To avoid this try getting up slowly. If you do feel dizzy, sit or lie down until the symptoms pass.
• This medicine may sometimes cause an increase in blood cholesterol levels, and for this reason your doctor may want to monitor your cholesterol levels while you are taking this medicine.
• Antidepressants may cause the amount of sodium in the blood to drop - a condition called hyponatraemia. This can cause symptoms such as drowsiness, confusion, muscle twitching or convulsions. Elderly people may be particularly susceptible to this effect. You should consult your doctor if you develop any of these symptoms while taking this medicine so that your blood sodium level can be checked if necessary.
• Following a review of data from clinical trials of venlafaxine in children under 18 years of age, the Committee on Safety of Medicines has concluded that venlafaxine is ineffective for treating depressive illness in this age group and actually increases the risk of harmful outcomes such as self-harm and potentially suicidal behaviour. Venlafaxine is not licensed for any use in children aged under 18 years and should not be used to treat depressive illness in this age group. It is not recommended for other uses in this age group as its safety and efficacy have not been established.

Use with caution in

• Elderly people.
• Young adults.
• History of suicidal behaviour or thoughts.
• History of mania or hypomania.
• People also receiving electroconvulsive therapy (ECT).
• People taking antipsychotic medicines.
• History of drug dependence or abuse.
• Decreased kidney function.
• Decreased liver function.
• Liver cirrhosis.
• History of fits (seizures), eg epilepsy.
• People at increased risk of bleeding.
• People taking medicine to prevent blood clotting (anticoagulants, eg warfarin).
• Heart disease.
• People who have recently had a heart attack.
• Raised pressure in the eye (intraocular pressure), eg glaucoma.
• People with a known risk for closed-angle glaucoma.

Not to be used in

• Children and adolescents under 18 years of age (see warning above).
• People who have taken a monoamine-oxidase inhibitor (MAOI) in the last 14 days (see below for more information).
• People with a very high risk of abnormal heart beats (ventricular arrhythmias), such as people with significant left-sided heart failure or uncontrolled high blood pressure (hypertension).
• Uncontrolled epilepsy.
• Breastfeeding.

This medicine should not be used if you are allergic to one orany of its ingredients. Please inform your doctor or pharmacist if you havepreviously experienced such anallergy. If you feel you haveexperienced an allergic reaction, stop using this medicine and inform yourdoctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy orbreastfeeding. However, other medicines may be safely used in pregnancy orbreastfeeding providing the benefits to the mother outweigh the risks to theunborn baby. Always inform your doctor if you are pregnant or planning apregnancy, before using any medicine.

• The safety of this medicine in pregnancy has not been established. It is not recommended for use during pregnancy unless considered essential by your doctor. There is the potential that the medicine could cause withdrawal symptoms in the new-born baby if the medicine is taken by the mother in the third trimester or up until birth. Seek medical advice from your doctor if you get pregnant or plan to have a baby while you are taking this medicine. If you get pregnant and decide to stop taking venlafaxine you should not do so suddenly - see the warning above about withdrawal symptoms.
• This medicine passes into breast milk. As this could be harmful to a nursing infant, mothers taking this medicine should either not breastfeed, or not take this medicine. This will depend on how important the medicine is for the mother's health. Seek medical advice from your doctor.

Label warnings

• Take this medication with or after food.
• Warning. May cause drowsiness. If affected do not drive or operate machinary.

Side effects

Medicines and their possible side effects can affect individualpeople in different ways. The following are some of the side effects that areknown to be associated with this medicine. Just because a side effect is statedhere does not mean that all people using this medicine will experience thator 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 sideeffects reported by the medicine'smanufacturer. For moreinformation about any other possible risks associated with this medicine,please read the information provided with the medicine or consult your doctoror pharmacist.

How can this medicine affect other medicines?

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

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

• 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 atleast one week after stopping venlafaxine. This is because using thesemedicines together can cause a serious and potentially life-threateninginteraction.

If venlafaxine is taken with other medicines that enhanceserotonin in the brain, there may be an increased risk of side effects such asagitation, restlessness and diarrhoea, known as the 'serotonin syndrome'. Othermedicines 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 withsibutramine.

Venlafaxine may increase the blood levels of the followingmedicines, and this may increase the risk of side effects from thesemedicines:

• clozapine
• haloperidol
• tricyclic antidepressants such as desipramine.

Venlafaxine may decrease the blood level of the anti-HIVmedicine, indinavir. This may possibly decrease the effectiveness of theindinavir, but the clinical importance of the interaction is not yetknown.

Cimetidine may increase the blood level of venlafaxine. This isnot usually a problem, but if you are elderly or have liver problems you shouldbe monitored more closely by your doctor if you are taking these two medicinestogether.

The antibiotic erythromycin and the antifungal ketoconazole mayalso increase the blood level of venlafaxine. These anti-infectives should beavoided where possible in people taking venlafaxine.

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

There may be an increased risk of bleeding if venlafaxine istaken by people who are taking any of the following medicines, which are knownto 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

Venlafaxine is also available as modified release capsules under the following brand names: