Venlafaxine (Effexor, Effexor XR) is an anti-depression and anti-anxiety medication. The drug is affecting the pain (increasing the pain tolerance) and it might be used to treat clinical neuropathic pain.
The most common side effects of venlafaxine are gastrointestinal problems: nausea, vomiting, diarrhea or constipation, anorexia, abdominal pain and flatulence. The medication affects the nervous system, causing both therapeutic and side effects. Patients frequently report dizziness, tiredness, sleeping problems, nervousness, anxiety, depression and decreased libido. Sometimes, venlafaxine might cause seizures, and the manufacturer recommends stopping the therapy in those patients. Antidepressants (including venlafaxine) often affect the sleep, causing sleep abnormalities. Patients may experience insomnia, somnolence, abnormal dreams or other sleep issues. Respiratory side effects are quite common and they include cases of pharyngitis, sinusitis and yawning, and rarely pneumonitis .
Venlafaxine is known to elevate the blood pressure, resulting in hypertension, and the condition is dose dependant. The medication increases the heart beat and pulse rate and may lead to cardio- and cerebro-vascular conditions. In regular therapeutic doses the use of this medication might lead to angina pectoris, angioedema, bradycardia, hypotension, arrhythmias, cerebral ischemia, cold feet or hands, and to severe heart problems, including infarction, coronary artery disease, congestive heart failure, heart arrest, etc. Many venlafaxine patients experience sweating, and some acne, contact dermatitis, pruritus, rash and redness of the skin, eczema, striae and some other skin problems. Patients treated with venlafaxine often report abnormal bleeding, usually ecchymosis (bruises). Alopecia (hair loss) is one of the known side effects of this drug, and the condition is reversible. New hair starts 2 to 4 weeks after the stop of venlafaxine.
Use of venlafaxine is affecting male and female sexual function, and is connected to the both increased and decreased libido, abnormal ejaculation, impotence and abnormal female orgasm. Asthenia (body weakness) is often reported in treated patients, and also headache, flu syndrome and some accidental injuries. The most severe muscular problem connected to venlafaxine is rhabdomyolysis. Psychiatric side effects could be hallucinations, mania, delusions, pschysosis or suicidal and homicidal ideas, depression or paranoid reactions. Ocular side effects are rare, most common are blurred vision and angle-closure glaucoma. Venlafaxine is known to affect the body weight. Some of the patients lose and other gain weight, during the treatment. The medication might be the reason for some metabolic changes, increase of cholesterol, lipids, enzymes in the blood and increase or decrease of blood sugar. Use of this drug is connected to the toxic hepatitis and it may have some effects to the endocrine system, causing galactorrhea and affecting the thyroid hormones.
In cases of overdose venlafaxine causes hypertension, tachycardia, mydriasis and transient arrhythmia.
If the medication is stopped suddenly there is a great chance that the patient would develop withdrawal symptoms. Severity of symptoms depends on the dose and length of the venlafaxine treatment and those usually includes headache, sweating, nausea, vomiting, diarrhea, tremor, agitation, anxiety. Symptoms usually last up to 48 hours after the last dose of venlafaxine and are improved once the therapy continues.