What is it used for?

• Schizophrenia.
• Treatment of psychotic or manic symptoms of schizoaffective disorder.

How does it work?

• Invega tablets contain the active ingredient paliperidone, which is a type of medicine called an atypical antipsychotic.
• Paliperidone works in the brain, where it affects various neurotransmitters, in particular dopamine and serotonin (5HT). Neurotransmitters are chemicals that are stored in nerve cells and are involved in transmitting messages between the nerve cells.
• Dopamine and serotonin are neurotransmitters known to be involved in regulating mood and behaviour, amongst other things. Psychotic illness is considered to be caused by disturbances in the activity of neurotransmitters (mainly dopamine) in the brain. Schizophrenia is known to be associated with an overactivity of dopamine in the brain, and this may be associated with the delusions and hallucinations that are a feature of this disease.
• Paliperidone works by blocking the receptors in the brain that dopamine acts on. This prevents the excessive activity of dopamine and helps to control schizophrenia.
• Schizophrenic patients may experience 'positive symptoms' (such as hallucinations, disturbances of thought, hostility) and/or 'negative symptoms' (such as lack of emotion and social withdrawal). Paliperidone is effective in relieving both positive and negative symptoms of schizophrenia, whereas older antipsychotics are usually less effective against the negative symptoms.
• Paliperidone also relieves 'affective symptoms' that are associated with schizophrenia, such as depression, guilt feelings or anxiety.
• Invega tablets are prolonged-release tablets. They are designed to release the paliperidone slowly and continuously to help provide steady blood levels of the medicine over 24 hours. These tablets must not be broken, crushed or chewed, as this would damage the prolonged-release action.

How do I take it?

• Invega tablets should be swallowed whole with liquid, in the morning. They must not be broken, chewed or crushed.
• The tablets can be taken either before or after breakfast, but it is important to stick to a set routine of either before or after breakfast, as otherwise the amount of medicine absorbed into the blood from the gut may fluctuate.
• If you forget to take a dose you should not take a double dose to make up for it. Just take your next dose as usual.
• Unless your doctor tells you otherwise, you should not suddenly stop taking this medicine, even if you feel better and think you don't need it any more. This is because the medicine controls the symptoms of the illness but doesn't actually cure it. This means that if you suddenly stop treatment your symptoms could come back. When treatment with this medicine is stopped, it should be done gradually, following the instructions given by your doctor.

Use with caution in

• Elderly people.
• Severely decreased liver function.
• Decreased kidney function.
• Diabetes.
• People with disease involving the heart and blood vessels (cardiovascular disease) for example heart failure, angina or previous heart attack.
• People with a personal or family history of an abnormal heart rhythm seen as a 'prolonged QT interval' on a heart monitoring trace or ECG.
• People taking other medicines that can increase the risk of a 'prolonged QT interval'.
• People with a history of stroke or mini-stroke (TIA).
• Elderly people with dementia and a risk of stroke (other similar antipsychotic medicines are associated with an increased risk of stroke and death in this group of people).
• People with a personal or family history of blood clots (venous thromboembolism), for example in a vein of the leg (deep vein thrombosis) or in the lungs (pulmonary embolism).
• People with other risk factors for getting a blood clot, for example smoking, being overweight, taking the contraceptive pill, being over 40, recent major surgery or being immobile for prolonged periods.
• People with low blood pressure (hypotension).
• People who are dehydrated.
• People with a history of seizures, eg epilepsy.
• People with conditions that increase the risk of epilepsy or convulsions, eg brain damage or withdrawal from alcohol.
• Parkinson's disease.

Not to be used in

• People who are allergic to risperidone.
• Breastfeeding.
• This medicine is not recommended for people who have any severe narrowing or blockage in their gut, or for people who have difficulty swallowing.
• This medicine is not recommended for people with severely decreased kidney function.
• This medicine is not recommended for children less than 15 years of age, as its safety and efficacy have not been established in this age group.
• Invega 3mg tablets contain lactose and should not be taken by people with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption. Other strengths of Invega do not contain lactose.
• This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.

If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

• The safety of this medicine during pregnancy has not been established. It should not be used in pregnancy, particularly in the first and third trimesters, unless considered essential by your doctor. If the medicine is used during the third trimester it could cause side effects or withdrawal symptoms in the baby after birth and the baby may need extra monitoring because of this.
• This medicine passes into breast milk and could be harmful to a nursing infant. It should not be used during breastfeeding. Mothers who need to take this medicine should not breastfeed and should bottle feed instead. 

Side effects

Very common

• Sleepiness or sedation.
• Difficulty sleeping (insomnia).
• Headache.
• Abnormal movements of the hands, legs, face, neck and tongue, eg tremor, twitching, rigidity (extrapyramidal effects).
• Increased salivation.
• Anxiety, restlessness and agitation (akathisia).

Common 

• Sore throat.
• Cough.
• Blocked nose.
• Infection of the breathing passages, eg sinusitis, flu, bronchitis.
• Dry mouth.
• Disturbances of the gut such as nausea, vomiting, constipation, diarrhoea, indigestion or abdominal pain.
• Changes in appetite or weight.
• Depression.
• Mania.
• Dizziness.
• Faster or slower than normal heart beat.
• Abnormal heart rhythm seen as a 'prolonged QT interval' on a heart monitoring trace or ECG.
• Drop in blood pressure causing dizziness that occurs when moving from a lying down or sitting position to sitting or standing.
• High blood pressure.
• Pain in the muscles, joints or back.
• Rash or itching.
• Feeling weak or tired.
• Fever.
• Stopping of menstrual periods in women.

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.

Paliperidone is a metabolite of risperidone and so may potentially cause some of the side effects reported with risperidone.

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?

There may be an increased risk of drowsiness and sedation if paliperidone is taken with any of the following (which can also cause drowsiness):

• alcohol
• barbiturates, eg amobarbital, phenobarbital
• benzodiazepines, eg diazepam, temazepam
• MAOI antidepressants, eg phenelzine
• sedating antihistamines, eg chlorphenamine, hydroxyzine
• sleeping tablets, eg zopiclone
• strong opioid painkillers, eg morphine, codeine
• tricyclic antidepressants, eg amitriptyline.

Paliperidone may enhance the blood pressure-lowering effects of medicines that lower blood pressure, including medicines used to treat high blood pressure (antihypertensives) and medicines that lower blood pressure as a side effect, eg benzodiazepines. If you are taking medicines that lower blood pressure you should tell your doctor if you feel dizzy or faint after starting treatment with this medicine, as your doses may need adjusting.

There may be an increased risk of abnormal heart rhythms (prolonged QT interval on a heart monitoring trace or ECG) if this medicine is taken in combination with any of the following medicines:

• antiarrhythmics (medicines to treat abnormal heart beats), eg amiodarone, procainamide, disopyramide, sotalol
• the antihistamines astemizole, mizolastine or terfenadine
• arsenic trioxide
• atomoxetine
• certain antidepressants, eg amitriptyline, imipramine, maprotiline
• certain antimalarials, eg halofantrine, chloroquine, quinine, mefloquine, Riamet
• certain other antipsychotics, eg thioridazine, haloperidol, sertindole, pimozide
• cisapride
• dronedarone
• droperidol
• intravenous erythromycin or pentamidine
• methadone
• moxifloxacin
• saquinavir.

There may also be an increased risk of a prolonged QT interval if medicines that can alter the levels of salts such as potassium or magnesium in the blood, eg diuretics such as furosemide, are taken in combination with paliperidone.

Paliperidone may oppose the effect of medicines for Parkinson's disease that work by stimulating dopamine receptors in the brain, for example levodopa, ropinirole, pergolide, bromocriptine.

Paliperidone may oppose the effect of anticonvulsant medicines used to treat epilepsy.

Paliperidone may increase blood sugar levels and disturb the control of diabetes. People with diabetes may need an adjustment in the dose of their antidiabetic medication.

Paliperidone may oppose the effect of histamine (used to treat leukaemia) and is not recommended for people having this treatment.

Medicines that may speed up the passage of Invega tablets through the gut, for example metoclopramide, could affect the absorption of paliperidone into the bloodstream.

The following medicines may speed up the breakdown of paliperidone in the body and so could make it less effective. If you take any of these medicines your doctor may need to increase your dose of paliperidone:

• carbamazepine
• rifampicin
• the herbal remedy St John's wort (Hypericum perforatum).
• This medicine should not be used in combination with risperidone.

References:

https://www.medbroadcast.com/drug/getdrug/invega

https://www.netdoctor.co.uk/medicines/brain-nervous-system/a8663/invega-paliperidone/

https://www.medicines.org.uk/emc/product/6816/smpc#gref

https://www.ema.europa.eu/en/documents/product-information/invega-epar-product-information_en.pdf

https://www.drugs.com/invega.html

https://www.webmd.com/drugs/2/drug-146745/invega-oral/details

https://www.rxlist.com/invega-drug.htm