How venlafaxine works
Venlafaxine is a drug from the group of selective serotonin-norepinephrine reuptake inhibitors (SSNRIs). It has an antidepressant (mood-lifting) and drive-increasing effect.
The two neurotransmitters serotonin and norepinephrine transmit nerve signals between brain cells by being released from one cell and then binding to specific docking sites (receptors) on the next cell. The neurotransmitters are then reabsorbed into the first nerve cell, thereby inactivating it.
Venlafaxine inhibits this reuptake, allowing norepinephrine and serotonin to remain active and thus effective for longer. The result is a mood-lifting and drive-increasing effect. The effect usually occurs with a time delay of about two weeks.
Absorption, breakdown and excretion
Venlafaxine is usually used in salt form as venlafaxine hydrochloride. It is absorbed into the blood via the intestinal wall after ingestion by mouth and metabolized primarily by the liver. Bioavailability is about 45 percent (meaning 45 percent of the amount of active ingredient taken by mouth can be utilized by the body). After metabolization by the liver, venlafaxine is largely excreted by the kidneys.
When is venlafaxine used?
Venlafaxine is approved for:
- Depression, including maintenance therapy to prevent recurrence of new depressive episodes.
- Generalized anxiety disorder
- @ Social anxiety disorder (social phobia)
- Panic disorder with/without claustrophobia (agoraphobia)
How venlafaxine is used
Venlafaxine is used in oral form as a tablet or capsule with or without delayed release (sustained release). Sustained-release preparations are taken only once daily, while those without sustained-release are taken two to three times daily.
For depressive syndromes as well as generalized anxiety disorder, therapy is usually with a dosage of 75 milligrams per day initially. If needed, the physician may increase the dose to 150 milligrams per day. The maximum dose is 375 milligrams per day.
Regular intake of venlafaxine is important for the success of the therapy, otherwise the amount of active norepinephrine and serotonin outside the nerve cells may decrease.
What are the side effects of venlafaxine?
Very often (that is, in more than one in ten people treated), taking venlafaxine causes headache, gastrointestinal upset (such as nausea, vomiting, and constipation), sweating, dry mouth, and an increased risk of tooth decay due to dry mouth.
Rarely (in one in ten to one hundred people treated), weight loss, unusual dreams, insomnia, and decrease in sexual desire (loss of libido) occur while taking venlafaxine.
Occasionally (in one in one hundred to one thousand people treated), venlafaxine may cause weight gain, skin reactions, orgasmic disturbances in women, and changes in taste.
What should be considered when taking venlafaxine?
Contraindications
Venlafaxine is contraindicated in:
- Hypersensitivity to the active substance or any of the other ingredients.
- concomitant use of a monoamine oxidase (MAO) inhibitor due to risk of serotonin syndrome
Serotonin syndrome is a life-threatening condition with increases in blood pressure, agitation, convulsions, and body overheating.
The antidepressant should be used with caution in the following cases:
- Suicidal thoughts (venlafaxine increases drive before its antidepressant effects kick in).
- @ epilepsy
- @ increased intraocular pressure (glaucoma)
Interaction
- Medicines to suppress the immune system (immunosuppressants such as tacrolimus, ciclosporin, sirolimus)
- antifungal drugs (antifungal drugs such as lotrimazole, ketoconazole, itraconazole)
- various antidepressants (e.g. amitriptyline, clomipramine, imipramine, citalopram, escitalopram, fluoxetine, norfluoxetine, sertraline)
- strong painkillers from the opiate/opioid group (e.g. alfentanil, codeine, fentanyl, methadone)
- cholesterol-lowering drugs (statins such as atorvastatin, lovastatin, simvastatin)
- erectile dysfunction drugs (sildenafil, tadalafil, vardenafil)
Judgment and reaction may be impaired, especially at the beginning of treatment and also when stopping venlafaxine.
Age Limitation
Venlafaxine is not recommended for the treatment of children and adolescents under 18 years of age. Efficacy and safety of the drug have not been adequately established in this age group.
Pregnancy and lactation
Various studies have provided no evidence of an increased risk of malformation with the use of venlafaxine. Therefore, use can be continued during pregnancy if the setting is stable.
For new-onset depression during pregnancy and breastfeeding, preference should be given to one of the better-studied agents, citalopram and sertraline.
How to obtain medication with venlafaxine
Venlafaxine is available by prescription in Germany, Austria, and Switzerland in all dosages. It may only be taken on a doctor’s instructions.
How long has venlafaxine been known?
Venlafaxine was approved in Germany in 1995 as the first drug from the group of selective serotonin-norepinephrine reuptake inhibitors. It was initially approved for the treatment of depression; later, other indications were added.
The patent expired in December 2008. Since then, numerous generics (preparations identical to the active ingredient) have come onto the market.
