Venlafaxine Side Effects

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Answer the side-effect intent for venlafaxine without diagnosing; distinguish common from serious reactions and give safe next-step/reporting guidance.

What is venlafaxine?

Venlafaxine contains the active ingredient Venlafaxine hydrochloride.

• Active ingredient — Venlafaxine hydrochloride
• Registration number — 43/1.2/0577; 43/1.2/0578; 43/1.2/0579; 52/1.2/0438
• Registration holder — Adcock Ingram Limited

It is approved for:

• Venlafaxine XR Adco is an antidepressant that belongs to a group of medicines called serotonin and norepinephrine reuptake inhibitors (SNRIs)
• This group of medicines is used to treat depression and other conditions such as anxiety disorders
• It is thought that people who are depressed and/or anxious have S5 lower levels of serotonin and noradrenaline in the brain
• It is not fully understood how antidepressants work, but they may help by increasing the levels of serotonin and noradrenaline in the brain

Common side effects of venlafaxine

Not everyone gets side effects. The effects below are those listed in the South African approved leaflet, grouped using the leaflet’s own frequency wording.

Frequent side effects

• decreased appetite
• difficulty sleeping
• abnormal dreams, nervousness
• decreased libido, abnormal ejaculation/orgasm (males)
• dizziness, drowsiness, shaking
• paraesthesia (abnormal sensation, typically tingling or pricking)
• altered taste
• blurred vision, dilated pupils, vision loss, inability of the eye to automatically change focus from distant to near objects
• hot flushes
• yawning
• nausea, dry mouth, constipation, vomiting, stomach pain
• an abnormally high level of muscle tone or tension, back pain
• inability to pass urine; difficulties passing urine
• impotence
• tiredness, lack of energy, pain
• weight gain, weight loss
• increased cholesterol

Less frequent side effects

• over activity, racing thoughts and decreased need for sleep (mania)
• feeling over-excited (hypomania)
• hallucinations
• derealisation (feeling that one’s surroundings are not real), apathy (lack of interest)
• abnormal orgasm
• involuntary muscle jerks or twitches; fits
• feeling dizzy (particularly when standing up too quickly)
• sensitivity to sunlight; bruising

Frequency unknown side effects

• sensation of whirling and loss of balance
• blood disorders such as granulocytes in the blood, deficiency of all types of blood cell caused by failure of bone marrow development, red cells, white cells, and platelets deficiency (pancytopaenia), platelets deficiency in the blood (thrombocytopaenia) (will be determined by a blood test)
• excessive water retention (known as SIADH)
• abnormal breast milk production
• decrease in blood sodium levels
• increased appetite
• confusion, feeling separated (or detached) from yourself
• agitation
• grinding of teeth (especially during sleep)
• headache
• a sensation of restlessness or an inability to sit or stand still
• involuntary movements of the muscles
• balance disorder
• muscular spasm and abnormal posture
• angle-closure glaucoma
• ringing in the ears
• low blood pressure
• inflammation of the lungs
• coughing, wheezing and shortness of breath which may be accompanied by a high temperature
• sore throat, runny nose, sneezing
• vomiting blood, black tarry stools (faeces) or blood in stools which can be signs of bleeding in the gastrointestinal tract
• severe abdominal or back pains, feeling sick and vomiting which could indicate inflammation of the pancreas
• diarrhoea
• severe weight loss (anorexia)
• indigestion, burping, wind (flatulence)
• increased liver function tests (determined by a blood test)
• itchiness, yellow skin or eyes, dark urine, or flu-like symptoms, which are symptoms of inflammation of the liver (hepatitis)
• excessive sweating (including night sweats)
• hives, hair loss, swelling of the legs and arms
• bulging, rash-like lesion that is red, pink, purple, or brown
• muscle pain
• increased frequency in urination
• involuntary leakage of urine
• menstrual irregularities such as increased bleeding or increased irregular bleeding
• chills
• unexpected bleeding, e.g. bleeding gums, blood in the urine or in vomit, or the appearance of unexpected bruises or broken blood vessels (broken veins)
• extended bleeding – if you cut or injure yourself, it may take slightly longer than usual for bleeding to stop
• heavy vaginal bleeding shortly after birth (postpartum haemorrhage)

Serious side effects and warning signs

This leaflet does not set out a separate list of serious side effects. The general warning signs below apply to any medicine.

General warning signs that apply to any medicine

How long can side effects last?

How long a side effect lasts depends on the effect, the product, how long it has been used, and the person. Some effects ease within days as the body adjusts. Others continue for as long as the product is used. A few can persist after stopping, and some need review rather than waiting.

• Settling effects — mild effects that ease over the first days or weeks of use
• Ongoing effects — effects that continue while the product is being used and improve after stopping
• Persistent effects — effects that continue after stopping and need medical review
• Delayed effects — effects that appear after weeks or months rather than immediately

Which of these applies to a particular effect is a clinical question. If a side effect is not settling, is getting worse, or is affecting your daily life, that is worth a conversation with a pharmacist or doctor regardless of how long it has been going on.

Factors that may affect side effects

The approved leaflet identifies the following cautions and factors.

Do not use it at all if

• if you are hypersensitive (allergic) to venlafaxine or to any of the other ingredients of Venlafaxine XR Adco (listed in section 6)
• if you are taking monoamine oxidase inhibitors (MAOI’s), a medicine also used to treat depression or Parkinson’s disease, or have taken it in the last 14 days (also, you must wait at least 7 days after you stop taking Venlafaxine XR Adco before you take any MAOI)
• if you are under the age of 18
• if you are pregnant or breastfeeding your baby

Use with care, and tell your doctor, if

• If you use other medicines that taken together with Venlafaxine XR Adco could increase the risk of developing serotonin syndrome
• If you have eye problems, such as certain kinds of glaucoma (increased pressure in the eye)
• If you have a history of high blood pressure
• If you have a history of heart problems
• if you have a history of myocardial infarction or unstable heart disease
• If you have a history of fits (seizures)
• If you have a history of low sodium levels in your blood (hyponatraemia)
• If you have a tendency to develop bruises or a tendency to bleed easily (history of bleeding disorders), or if you are taking other medicines that may increase the risk of bleeding e.g., warfarin (used to prevent blood clots)
• If you are pregnant as there may be an increased risk of heavy vaginal bleeding shortly after birth
• If you have a history of high cholesterol
• If you are taking weight loss medicines
• If you have a history of, or if someone in your family has had, mania or bipolar disorder (feeling over- excited or euphoric)
• If you have a history of aggressive behaviour
• If you need to have screening tests for phencyclidine and amphetamine. Thoughts of suicide and worsening of your depression or anxiety disorder If you are depressed and/or have anxiety disorders, you can sometimes have thoughts of harming or killing yourself. These may be increased when you first start taking antidepressants, since these medicines all take time to work, usually about two weeks, but sometimes longer. You may be more likely to think like this:
• If you have previously had thoughts about killing yourself or harming yourself
• If you are a young adult. Information from clinical trials has shown an increased risk of suicidal behaviour in young adults (less than 25 years old) with psychiatric conditions who were treated with an antidepressant. If you have thoughts of harming or killing yourself at any time, contact your doctor or go to a hospital straight away. Dry mouth Venlafaxine XR Adco may cause a dry mouth, this may increase the risk of caries and dental hygiene is very important. Diabetes Your blood glucose levels may be altered due to Venlafaxine XR Adco. Therefore, the dosage of your diabetes medicines may need to be adjusted. Sexual problems Venlafaxine XR Adco (so called SNRIs) may cause symptoms of sexual dysfunction. In some cases, these symptoms have continued after stopping treatment. Talk to your doctor before taking Venlafaxine XR Adco, especially if you have:
• History of bleeding disorders, or if you are pregnant Children and adolescents Do not give Venlafaxine XR Adco to children and adolescents under the age of 18 years. Suicide-related behaviours (suicide attempt and suicidal thoughts) and anger (predominantly aggression, oppositional behaviour and anger) were more frequently observed among children and adolescents

Pregnancy and breastfeeding

• If you are pregnant or breastfeeding, think you may be pregnant or are planning to have a baby, please consult your doctor, pharmacist or other healthcare provider for advice before taking Venlafaxine XR Adco
• Pregnancy Do not take Venlafaxine XR Adco if you are pregnant
• If your baby was exposed to Venlafaxine XR Adco late in the third trimester, your baby might have symptoms of not feeding properly when born
• If your baby has these symptoms when it is born and you are concerned, contact your doctor and/or midwife who will be able to advise you
• If you take Venlafaxine XR Adco near the end of your pregnancy there may be an increased risk of heavy vaginal bleeding shortly after birth, especially if you have a history of bleeding disorders
• Your doctor or midwife should be aware that you are taking Venlafaxine XR Adco so they can advise you

Interactions and medicines to check

The approved leaflet names these interactions.

• Monoamine Oxidase Inhibitors (MOAI) which are used to treat depression or Parkinson’s disease must not be taken with Venlafaxine XR Adco. Tell your doctor if you have taken these medicines within the last 14 days (MAOIs: see the section What you need to know before you take Venlafaxine XR Adco)
• Serotonin syndrome: A potentially life-threatening condition or Neuroleptic Malignant Syndrome (NMS)-like reactions may occur with Venlafaxine XR Adco treatment, particularly when taken with other medicines. Examples of these medicines include:
• Triptans (used for migraine)
• Other medicines to treat depression, for instance SNRIs, SSRIs, tricyclics, or medicines containing lithium
• Medicines containing amphetamines (used to treat attention deficit hyperactivity disorder (ADHD), narcolepsy and obesity)
• Medicines containing sibutramine (used for weight loss)
• Medicines containing tramadol, fentanyl, tapentadol, pethidine, or pentazocine (used to treat severe pain)
• Medicines containing linezolid, an antibiotic (used to treat infections)
• Medicines containing moclobemide, a MAOI (used to treat depression)
• Medicines containing dextromethorphan (used to treat coughing)
• Medicines containing methadone (used to treat opioid drug addiction or severe pain)
• Medicines containing methylene blue (used to treat high levels of methaemoglobin in the blood)
• Products containing St. John’s Wort (also called Hypericum perforatum, a natural or herbal remedy used to treat mild depression)
• Products containing tryptophan (used for problems such as sleep and depression)
• Antipsychotics (used to treat a disease with symptoms such as hearing, seeing or sensing things which are not there, mistaken beliefs, unusual suspiciousness, unclear reasoning and becoming withdrawn) Signs and symptoms of serotonin syndrome may include a combination of the following: restlessness, hallucinations, loss of coordination, fast heartbeat, increased body temperature, fast changes in blood pressure, overactive reflexes, diarrhoea, coma, nausea, vomiting. In its most severe form, serotonin syndrome can resemble Neuroleptic Malignant Syndrome (NMS). Signs and symptoms of NMS may include a combination of fever, fast heartbeat, sweating, severe muscle stiffness, confusion, increased muscle enzymes (determined by a blood test)
• Tell your doctor immediately or go to the casualty department at your nearest hospital if you experience any of the above symptoms. You must tell your doctor if you are taking medicines that can affect your heart rhythm such as:
• Anti-dysrhythmics such as quinidine, amiodarone, sotalol or dofetilide (used to treat abnormal heart rhythm)
• Antipsychotics such as thioridazine
• Antibiotics such as erythromycin or moxifloxacin (used to treat bacterial infections)
• Antihistamines (used to treat allergy) The following medicines may also interact with Venlafaxine XR Adco and should be used with caution. It is especially important to mention to your doctor or pharmacist if you are taking medicines containing:
• Ketoconazole (an antifungal medicine)
• Cimetidine (an antacid), especially if you are elderly or have liver problems
• Imipramine, bupropion or fluoxetine (antidepressants)
• Ritonavir (an antiretroviral used for HIV/AIDS)
• Haloperidol or risperidone (to treat psychiatric conditions)
• Metoprolol (a beta blocker to treat high blood pressure and heart problems) Venlafaxine XR Adco with food and alcohol You should not take any alcohol when taking Venlafaxine XR Adco

What to do if you experience side effects

If you think you are having a side effect, the response depends on how severe it is. Use the warning signs above first — if any of those apply, treat it as urgent.

If the symptom is severe or frightening

Get medical help immediately. Call 10177 for an ambulance, or 112 from a mobile phone, or go to the nearest emergency department. Take the product and its packaging with you if you can.

If the symptom is mild but bothering you

• Write down what the symptom is, when it started, and how it relates to when you take the product
• Check the leaflet that came with the product to see whether the symptom is listed
• Speak to your pharmacist — for many questions this is the fastest route to a useful answer
• Contact the prescriber if the symptom is affecting your daily life or is not settling

You can also report a suspected side effect in South Africa. Reporting does not replace getting medical advice, and you do not need to be certain the product was the cause.

When to seek urgent medical help

Some symptoms need medical attention straight away rather than an appointment in a few days. Do not wait to see whether they settle.

Get same-day medical advice if you have

• A high fever, or a rash together with feeling generally unwell
• Yellowing of the eyes or skin, or unusually dark urine
• Unusual bruising or bleeding that you cannot explain
• Severe or persistent vomiting or diarrhoea, especially if you cannot keep fluids down
• A sudden change in mood, or thoughts of harming yourself
• Any symptom that is rapidly getting worse

How to report a suspected side effect in South Africa

South Africa has an official system for reporting suspected side effects, run by the South African Health Products Regulatory Authority (SAHPRA). Reports from the public and from healthcare professionals are how safety signals get detected after a product is already in use.

Who can report

Anyone can report — you do not have to be a healthcare professional, and you do not need to prove that the product caused the problem. A suspicion is enough. Patients, caregivers and family members can all submit a report.

What to have ready

• The name of the product, its strength and form, and the batch number if you have it
• Why it was being used, and when it was started and stopped
• What the suspected reaction was, when it began, and how long it lasted
• Any other medicines, supplements or remedies being used at the same time
• Basic details about the person affected — age and sex are usually enough

How to report

SAHPRA accepts adverse reaction reports through its e-Services reporting system and through the Med Safety mobile app. Healthcare professionals can also report through the same routes. Current forms and access points are published on the SAHPRA site.

• SAHPRA Health Products Vigilance — the main vigilance and reporting hub
• SAHPRA e-Services — current adverse reaction reporting access

For a fuller walkthrough see how to report an adverse drug reaction.

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