There are a number of different SNRI antidepressants.
|Brand name||Chemical name|
|Mirtazapin - closely related but not identical to SNRI|
Serotonin and noradrenaline (also called norepinephrine) are neurotransmitters made by the cells in the brain. Neurotransmitters are chemicals used by brain cells to connect and communicate with each other. SNRI antidepressants slow the rate that the brain breaks down serotonin and noradrenaline. This leads to an increase in serotonin and noradrenaline activity in the brain. (Mirtazapine has a similar effect by a slightly different mechanism.) This has been shown to improve symptoms of depression and anxiety. It also reduces obsessions and compulsions in obsessive-compulsive disorders (OCD).
Common side effects include:
Interactions with other drugs that affect serotonin can cause a serotonin syndrome. This syndrome involves fever, muscle shakes and seizures. It can be extremely serious and has caused deaths. Another serious problem that can occur is lowered sodium (salt) in the blood (Venlafaxine (Efexor)) SNRIs can also cause raised blood pressure. Lowered blood white cells can occur with Mirtazapine (Remeron/Avanza).
If changing between medications be careful that the overlap of medications does not cause too much serotonin activity. Fluoxetine leaves the body slowly and may exert its effect for more than three days.
SNRIs are usually safe. Overdose causes nausea and drowsiness. Deaths have been reported with very large overdoses.
Apart from the serotonin syndrome, some of the SNRI antidepressants slow the rate at which the body breaks down other medications. This may raise levels of medications such as:
It may be necessary to adjust the dose of other medications when a person is taking an SNRI.
SSRIs must not be taken at the same time as or soon after using Monoamine-oxidase inhibiting drugs (Parnate and Nardil).
There are no scientific studies of the effect of SNRIs on the human foetus. Animal studies show adverse effects at high doses. SNRI antidepressants should be used in pregnancy only if this is necessary for the health of the mother. SNRI antidepressants appear in breast milk. The manufacturers of Venlafaxine (Efexor) recommend that it Efexor be stopped if breast feeding is continuing. No information is available for Nefazadone (Serzone) or Mirtazapine (Remeron/Avanza).
Antidepressants are not addictive. However, you may experience some withdrawal effects on stopping your antidepressant. Reactions vary between medications and between people. All SNRIs have been reported to produce some withdrawal effects - physical discomfort, restlessness and flu-like symptoms - if suddenly stopped. These symptoms are reduced by stopping the medication gradually (over 2 weeks from higher doses). Don't stop taking your medication without seeing a doctor first.
Often the starting dose does not need to be increased. However, sometimes higher doses are needed. Some people break down the medications faster than others and need higher doses.
Tablets are usually taken in the morning as many people find later doses interfere with sleep. However, this is very variable and some people find the medications make them sleepy and, so take them at night. The time of day does not change the effectiveness of the medication.
Food does not affect the absorption of Venlafaxine (Efexor) or Mirtazapine (Remeron/Avanza) so these medications can be taken before or after food. Nefazadone (Serzone) may be less absorbed so should be taken before food.
If a dose is missed, take it as soon as possible. If a night-time dose is missed do not take it in the morning but take only the ordinary night-time dose the next night.
|Name||Chemical name||Common dose||Most common time of dose|
|Efexor||Venlafaxine||75 mgm - 300 mgm||Morning|
|Nefazadone||Serzone||200mgm - 600 mgm||Morning|
|15 mgm - 45 mgm||Evening|
You will need to take the antidepressant for at least 6 to 9 months after your symptoms disappear. Stopping your antidepressant too early increases your chances of suffering a recurrence of depression.
SSRIs have been in use for more than 7 years. Some people have taken them for that length of time. No extra problems have emerged beyond the common side effects mentioned above.
Last reviewed and updated: 8 February 2006