Generality
Venlafaxine is an active ingredient used in the treatment of depressive disorders and anxiety states .
This molecule, therefore, is able to exert both an antidepressant and anxiolytic action, mainly as a function of the dosage administered to the patient.
More in detail, venlafaxine is a selective inhibitor of serotonin and noradrenaline reuptake . The inhibitory action is exercised through the inhibition of the activity of the transporters assigned to the re-uptake of the neurotransmitters mentioned above (SerT and NET, respectively).
Venlafaxine was introduced to the US market in 1993 by the pharmaceutical company Wyeth (subsequently purchased by Pfizer) under the trade name of "Efexor". In Italy, the date of the first marketing authorization for this medicinal product based on venlafaxine dates back, instead, to 1998.
Examples of Specialties Venlafaxine-containing medicines
- Efexor®
- Ixilania®
- Zaredrop®
Therapeutic indications
When is the use of Venlafaxine indicated?
The administration of venlafaxine is indicated:
- In the treatment of major depression episodes;
- In the prevention of recurrences of major depression episodes;
- In the treatment of anxiety disorders, such as:
- Generalized anxiety disorder;
- Social anxiety disorder;
- Panic disorders (panic attacks), with or without agoraphobia.
Warnings
Warnings and Precautions for the use of Venlafaxine
Before taking venlafaxine medicines, you must tell your doctor if you are in one or more of the following conditions:
- You are being treated with medicines able to increase serotoninergic transmission and / or able to alter the heart rhythm (to find out what they are, see the following chapter "Pharmacological Interactions");
- You suffer from heart disease (including changes in heart rhythm), hypertension or other disorders of the vascular system ;
- One suffers, or has suffered in the past, from hyponatremia ;
- There is a tendency for bleeding to develop and / or you are on medication that can increase the risk of bleeding (such as, for example, anticoagulants);
- One suffers or has a history of seizures ;
- One is suffering from eye diseases such as glaucoma;
- There is a history of aggressive behavior ;
- There is a family history of mania or bipolar disorder .
Did you know that ...
The intake of venlafaxine may cause changes in blood glucose levels, therefore, in diabetic patients it may be necessary to adjust the dosages of the antidiabetic therapy to which they are subjected.
Suicidal thoughts
Patients with psychiatric disorders, such as anxiety and especially depression, are exposed to an increased risk of suicidal thoughts and / or behavior and an increased risk of self - harm . Since the effect of venlafaxine is not immediate but takes a few weeks to establish itself, it may be useful to monitor patients until there is an improvement in anxiety or depression. The same patients can seek help by talking to their doctor or family members.
Use in children and adolescents.
Venlafaxine should not be given to children and adolescents under 18 years of age. However, the final decision is always up to the doctor, after a careful evaluation of the patient.
Please note
Venlafaxine is able to interfere with the ability to drive and use machines . Therefore, these activities should not be performed during therapy with this active ingredient.
Pharmacological Interactions
Interactions between Venlafaxine and Other Drugs
Due to the dangerous and sometimes fatal drug interactions that can occur, venlafaxine should not be taken in combination with drugs capable of increasing serotonergic transmission, such as:
- Monoamine oxidase inhibiting drugs (MAOIs);
- Selective serotonin reuptake inhibitors (SSRIs);
- Triptans, drugs used to treat migraine;
- Tricyclic antidepressants (TCA);
- Antipsychotics ;
- Tramadol and other opioid analgesics ;
- Tryptophan- based medicines;
- Dextromethorphan-based medicines;
- Methadone- based medicines;
- Methylene blue based products
- Preparations based on St. John's Wort (or St. John's wort), a plant with antidepressant properties.
Also, before taking venlafaxine you need to tell your doctor if you are taking drugs that can alter your heart rhythm, what are the antiarrhythmics, some types of antihistamines, some types of antibiotics (such as macrolides and quinolones) and some types of antipsychotics .
Finally, we recall that also the intake of azole antifungals, antivirals and metoprolol can interfere with the activity of venlafaxine.
If you are taking one or more of the above mentioned drugs, you should inform your doctor before starting treatment with venlafaxine.
However, your doctor must also be informed if you are taking - or have recently been taken - drugs or substances of any other type, including non-prescription medicines (SOP), OTC drugs, or herbal and herbal products and homeopathic products.
Side effects
Side effects caused by the intake of Venlafaxine
Venlafaxine can cause side effects just like any other drug. However, these effects do not occur equally in all individuals. In fact, not all patients experience side effects or manifest them in the same way, as each person responds differently to the administration of the drug.
However, the main side effects that can occur during venlafaxine therapy are listed below (to obtain more detailed information, we recommend reading the package insert for the medicinal product prescribed by the doctor).
Psychiatric disorders
The side effects that venlafaxine can cause psychically are manifold and consist of:
- Confusion;
- depersonalization;
- Nervousness;
- Insomnia;
- Libido reduction and anorgasmia;
- Hallucinations and derealization;
- Mania.
Furthermore, in some cases, subtle and aggressive ideas may also occur.
Nervous system disorders
Venlafaxine therapy can also lead to the appearance of disorders affecting the nervous system, such as:
- Headache;
- dizziness;
- Drowsiness;
- Tremors;
- Hypertonia;
- paresthesia;
- myoclonus;
- Psychomotor restlessness;
- Balance disorders;
- dysgeusia;
- Syncope;
- Convulsions.
Cardiovascular disorders
Treatment with venlafaxine may cause palpitations, tachycardia, vasodilation, hypotension and orthostatic hypotension.
Eye disorders
Venlafaxine therapy can cause various problems also at the ocular level, giving rise to side effects such as blurred vision, accommodation disorders and mydriasis. In rare cases, the active ingredient may also favor the appearance of closed-angle glaucoma.
Gastrointestinal disorders
During treatment with venlafaxine the following side effects of the digestive system may occur:
- Dry mouth (this side effect increases the risk of onset of dental caries, for this reason, it is recommended to maintain an accurate oral hygiene);
- Nausea and / or vomiting;
- Diarrhea or constipation;
- Gastrointestinal bleeding.
Urinary tract disorders
Venlafaxine therapy may cause dysuria and incontinence or urinary retention.
Other side effects
Other side effects that could occur with venlafaxine are:
- Even severe allergic reactions in sensitive individuals, angioedema and Stevens-Johnson syndrome;
- Photosensitivity reactions;
- Hyponatremia;
- Alopecia;
- Appetite reduction;
- Tinnitus and vertigo;
- Hyperhidrosis and night sweats;
- Changes in liver function;
- Menorrhagia or metrorrhagia;
- Premature ejaculation or erectile dysfunction;
- Fatigue and fatigue;
- Increase in body weight and cholesterolemia.
Serotonin syndrome
Like many serotonin reuptake inhibitors, venlafaxine can potentially give rise to serotonin syndrome or serotonin poisoning . The risk of developing this syndrome - characterized by an excess of serotoninergic activity at central level - increases if the active ingredient in question is administered in combination with other drugs capable of enhancing the serotonin signal.
The serotonin syndrome can occur in mild, moderate or severe form and the symptoms that characterize it usually appear very quickly.
As for the mild form, the patient can manifest:
- Tachycardia;
- Chills;
- Increased sweating;
- Headache;
- mydriasis;
- Tremors;
- muscle twitching;
- spasms;
- Accurate reflexes.
In the case of moderate intoxication, however, they can occur:
- Accentuation of intestinal sounds (borborigmas);
- Diarrhea;
- Hypertension;
- Temperature.
Finally, when the syndrome manifests itself in severe form, there is a marked increase in heart rate and blood pressure. The patient may also enter a state of shock with body temperatures exceeding 40 ° C. In addition, rhabdomyolysis (rupture of skeletal muscle cells and their release into the bloodstream), convulsions and renal failure may occur.
Abstinence symptoms
Discontinuation of venlafaxine therapy, especially if abrupt, can lead to withdrawal symptoms which consist of:
- dizziness;
- paresthesia;
- Sleep disorders;
- Asthenia;
- Anxiety;
- agitation;
- Nausea and / or vomiting;
- Tremors;
- Headache.
Generally, these symptoms occur in mild form and are self-limiting, but in some patients they may also occur severely.
Overdose
In the event of an overdose of venlafaxine it is possible to experience vomiting, tachycardia or bradycardia, hypotension, convulsions and altered state of consciousness. In the most serious cases, death may also occur.
Therefore, in case of ingestion of excessive doses of venlafaxine, it is necessary to immediately contact the medical help, or go to the nearest emergency room bringing the medicine pack with you.
Action mechanism
How does Venlafaxine work?
Venlafaxine is a selective inhibitor of serotonin and noradrenaline reuptake (NSRI), two neurotransmitters whose deficiency is thought to be responsible for the onset of psychiatric disorders such as depression (monoaminergic hypothesis). The onset of anxiety disorders, on the other hand, seems to be correlated above all to a deficit of serotonin and not of noradrenaline.
However, both venlafaxine and the main product of its metabolism - O-desmethylvenlafaxine (ODV) - are able to interact with transporters assigned to serotonin and noradrenaline reuptake - respectively, SerT and NET - hindering its activity . Thanks to this mechanism of action, the aforementioned neurotransmitters remain in the synaptic wall for a longer period of time with a consequent increase in serotoninergic and noradrenergic transmissions and improvement in the symptoms of psychiatric disorders for which the use of the drug is indicated.
Please note
Venlafaxine does not inhibit serotonin and noradrenaline transporters in equal measure, but has a greater affinity for SerT (the serotonin transporter).
Not surprisingly, at relatively low doses - up to 150 mg per day - the active ingredient in question acts mainly as a selective inhibitor of serotonin reuptake, while at higher doses it is also able to inhibit noradrenaline reuptake.
Method of use and Posology
How to take Venlafaxine
Venlafaxine is available in pharmaceutical formulations suitable for oral administration, such as tablets, prolonged-release tablets, capsules, controlled-release hard capsules and oral solution.
The tablets and capsules should be swallowed whole with the help of a drink of water; while the oral solution must be previously diluted in water. The drug should be taken at the same time every day, preferably in the morning or evening.
Please note
Venlafaxine should be taken on a full stomach . Furthermore, it should be remembered that during therapy with this active ingredient alcohol consumption MUST BE AVOIDED .
The dose of venlafaxine to be administered to each patient must be established by the doctor on a strictly individual basis. However, the usual starting dose is 37.5-75 mg of active ingredient per day. After that, the doctor will gradually increase the amount of drug to be administered until the optimal dosage is reached which allows the patient to control the symptomatology.
Usually, the maximum achievable dosage for treating depressive disorders is 375 mg of venlafaxine per day; while for the treatment of anxiety disorders, the maximum daily dose is 225 mg.
In no case should the treatment be suspended without the doctor's express indication.
Pregnancy and breastfeeding
Can Venlafaxine be taken during pregnancy and during breastfeeding?
The use of venlafaxine during pregnancy increases the risk of onset of persistent pulmonary hypertension in the newborn, a serious condition that occurs within 24 hours after the birth of the child. Therefore, before taking medicines containing venlafaxine, you must inform your doctor of your pregnancy. This health figure will establish - after a careful evaluation of the relationship between the possible risks to the fetus / newborn and the expected benefits for the mother - whether venlafaxine can be taken by the pregnant woman or not.
As for nursing mothers, venlafaxine is excreted in breast milk . Therefore, before taking this active ingredient you must tell your doctor if you are breast-feeding. Also in this case, it will be the latter who decides whether the mother can continue breastfeeding, or whether she must stop breastfeeding to take venlafaxine.
Contraindications
When Venlafaxine should not be used
The use of medicinal products based on venlafaxine is contraindicated:
- In case of known hypersensitivity to venlafaxine and / or to one or more of the excipients contained in the medicinal product to be taken;
- In patients on therapy - or who have taken less than 14 days - monoamine oxidase inhibitors (used in the treatment of depressive disorders and Parkinson's disease) or other drugs able to increase serotonin transmission .
