How Venlafaxine Works
Venlafaxine works by making more serotonin and norepinephrine available in the body. Unlike the other SNRIs, Venlafaxine inhibits more serotonin reuptake than norepinephrine. This causes more serotonin to be available in the body.
Storage, Dosage & How to use Venlafaxine
Venlafaxine comes in 25mg, 37.5mg, 50mg, 75mg, and 100mg tablets. The tablets are pale peach colored, and shield shaped with a flat-face bevelled edge. The recommended starting dose is 75mg per day, taken in two to three doses with food. Take this medication at the same time each day. Store the medication away from moisture and heat.
If the tablet or capsule is difficult to swallow – do not chew or crush it. If you have the capsule, open it into a spoonful of apple sauce, then swallow immediately without chewing.
Depending on how the drug is tolerated and whether or not the desired effect is achieved, the dose may be increased to 150mg per day. The dosage must be increased over a period longer than four days. Maintenance doses may be 75mg to 225mg per day, depending on individual diagnoses.
The most common side effects are:
- headache, dizziness, drowsiness, tiredness
- anxiousness, nervousness, jittery
- sleep disturbances, unusual dreams
- fast heart rate, blurred vision
- nausea, vomiting, diarrhea, constipation
- changes in weight and appetite
- dry mouth, yawning
- increased perspiration
- sexual problems
Other common side effects, not listed here, might occur. Sleep, appetite, and level of energy usually improve within one to two weeks. Contact your provider for any unusual symptoms or changes.
The most serious side effects that require emergency assistance are:
- suicidal ideation in young patients
- allergic reaction
- hives, rash
- difficulty breathing
- swelling of the face, tongue, throat
- serotonin syndrome
Serotonin syndrome is a dangerous-to-life side effect that requires urgent care. Read in the Interactions and Contraindications sections for the progression of symptoms caused by Serotonin syndrome.
Other possible serious side effects that require immediate medical help:
- Nose bleeds, bleeding gums, abnormal vaginal bleeds, any bleeding that will not stop
- Headache, confusion, problems thinking or remembering, weakness, unsteady gait
- Blurred vision, eye pain, red eyes, seeing halos around lights
- Cough, chest tightness, trouble breathing
- Rigid muscles, high fever, sweating, confusion, fast or uneven heart rate, tremors, feeling faint
Should any of the above serious effects occur, contact your prescribing Provider immediately. For allergic reactions, contact emergency services immediately. In the case of serotonin syndrome, contact your Provider immediately and follow their instructions.
Warnings & Precautions
Some foods, herbal products, and other medications increase serotonin. Ingested while receiving Venlafaxine therapy, serotonin may increase rapidly in the body. Serotonin syndrome is a life-endangering effect of too much serotonin. Symptoms range from mild to severe, and possibly death. Before beginning Effexor treatment, inform your Prescribing Provider of all medications, supplements, and herbal products(including caffeine) that you are currently taking.
In children, teens, and young adults, Venlafaxine may initially increase suicidal thoughts and feelings when beginning this therapy. Suicidal ideation may also increase at any time of the therapy if the dosage is altered. Observe for new or sudden mood swings, behavior, the expression of worsening depression or suicidal thoughts. Contact the prescribing Provider immediately should this occur.
Danger of Weaning Too Quickly
To stop taking Venlafaxine, you and your Provider must create a weaning program, because it is NOT safe to stop the medication in one day. Stopping the medication too quickly can cause agitation, headaches, dizziness, confusion, nightmares, nausea, vomiting, diarrhea, and tingling electric sensations. Stopping this medicine too quickly can cause a relapse of depression.
Narrow Angle Glaucoma
Do NOT take this medication if you have uncontrolled narrow-angle glaucoma.
Use of MAO Inhibitors
Do NOT use Venlafaxine within seven days before, or for 14 days after, taking an MAO inhibitor.
Do NOT take this medication if you have had allergic reactions to Venlafaxine(Effexor) or to desvenlafaxine(Pristiq).
Before beginning Venlafaxine, tell the Provider if you are using stimulants, opioids, NSAIDs, herbal remedies, other anti-depressants or mental illness medications. Also report medications taken for Parkinson’s disease, migraine headaches, serious infections, or medications that prevent nausea and vomiting. Medications for these conditions used with Venlafaxine can cause serotonin syndrome. Serotonin syndrome is a life-endangering effect of too much serotonin. Symptoms range from mild to severe, and possibly death.
Newborns of mothers taking Venlafaxine late in the third trimester may require prolonged hospitalization, respiratory support, and tube feedings after birth.
Do not breast feed when receiving Venlafaxine therapy.
Venlafaxine may increase blood pressure. High blood pressure typically has no noticeable symptoms. Monitor blood pressure vigilantly, especially when beginning use of this therapy. Discuss changes with the Provider to manage hypertension.
Be aware that this drug can cause false results on drug-screening urine lab tests.
Also, avoid activities such as driving or managing heavy equipment and machinery, until your body adjusts to the medication. Reaction time may be impaired.
Venlafaxine is not advised with certain health conditions. Discuss the benefits and risks of receiving Venlafaxine therapy with your prescribing Provider, if you have any of the following:
- narrow angle glaucoma
- liver disease
- kidney disease
- bipolar disorder
- chronic pain
- heart disease
- high cholesterol
- thyroid disorder
- bleeding problems
- low levels of sodium
A number of medications given for these conditions can also interfere with the safe and effective use of Venlafaxine. Review all of your medications with the healthcare provider. The following are known to have adverse interactions with Venlafaxine:
- Anti-inflammatory drugs(NSAIDs)
- MAO Inhibitors
Also, be aware that any stimulant can increase the effect of venlafaxine causing dangerous symptoms to escalate.
Using any medication or product that increases uptake of serotonin
Symptoms may begin with diarrhea, shivering, increased anxiety, agitation, restlessness, insomnia, headaches, rigid muscles, mild fever, and goosebumps.
Signs of serotonin syndrome worsening begin with increasing the heart rate and blood pressure. The patient’s pupils may become dilated. There will be a loss of muscle coordination, twitching, heavy perspiration, and confusion.
Severe serotonin syndrome symptoms include high fever, seizures, irregular heartbeat with unconsciousness, and eventually death, if untreated.