One reader asked whether it would be safe to abruptly stop use of an antidepressant medication. As a general rule, it's not a good idea to do so.
One of the reasons why it's not a good idea: you may experience "Withdrawal Symptoms" (also known as "Discontinuation Symptoms").
Withdrawal symptoms may begin anywhere from 24 hours to 1 week after stopping antidepressant medications. The time frame depends on the each medication's "elimination half-life" (how long it takes for half of the drug to be eliminated from the body).
In a nut shell:
Short half-life = more likely to experience withdrawal symptoms
Long half-life = less likely to experience withdrawal symptoms
You can think of it this way:
McDonald's large size portion of french fries typically contains about 90 french fries.
Imagine that McDonald's decided to start giving fewer french fries per order.
In one scenario, they might reduce the number of french fries by 1 french fry per day.
It would take 45 days (1.5 months) for the number of fries in the order to be reduced by half.
In another scenario, they might reduce the number of fries by 1 french fry per week.
It would take 45 weeks (over 10 months) for the number of fries in the order to be reduced by half.
Customers are more likely to notice that McDonald's is "under-filling" their french fries sooner when the amount of fries served is cut in half over the course of 1.5 months (i.e., a shorter "half life"). It would likely take longer for customers to notice that fries are missing from their order if the amount of fries served is very gradually cut in half over the course of 10 months (i.e., a longer "half life").
Similarly, a person's body is more likely to "notice it" when a medication is more quickly removed from the body.
Withdrawal symptoms may include:
Flu-like symptoms (Nausea, Upset stomach, Sweating, Flushing)
Troubles sleeping, Unusual dreams
Dizziness, Light-headedness
Tremor (shakiness)
Anxiety, Agitation, Depression, Irritability
"Brain Zaps" (strange, painless electric jolt-like sensations in your head/body)
Post-SSRI Sexual dysfunction (increased or decreased libido, arousal, orgasm, genital sensations)
Withdrawal symptoms may be uncomfortable. They may be a nuisance.
They are unlikely to be dangerous or life-threatening (unless perhaps you were operating heavy machinery and suffered a bout of significant dizziness or shakiness, or something of that sort).
The discontinuation symptoms would disappear quickly if you resumed use of the antidepressant medication. Even if you don't resume use of the antidepressant medication, the discontinuation symptoms will resolve over time as your body readjusts.
Which antidepressant medications are the biggest "offenders"?
Paxil and Venlafaxine.
Due to their short half-lives, just one late or missed dose can cause withdrawal symptoms.
Prozac, on the other hand, has the longest half-life.
Abrupt discontinuation of Prozac (even high doses of Prozac) is unlikely to cause withdrawal symptoms at all.
If someone is having a hard time tapering off of Paxil or Venlafaxine because of uncomfortable withdrawal side-effects, one option may be to switch from the Paxil/Venlafaxine over to Prozac. Then taper and discontinue the Prozac.
It is also possible to use a liquid formulation of an antidepressant medication which allows you to more gradually reduce the dose one drop at a time (like taking out just one french fry from a serving at a time!).
Venlafaxine (Effexor) half-life = 5 hours, 99% out of body in 1 day
Duloxetine (Cymbalta) half-life = 12 hours, 99% out of body in 2.5 days
Desvenlafaxine (Pristiq) half-life = 12 hours, 99% out of body in 2.5 days
Paroxetine (Paxil) half-life = 24 hours, 99% out of body in 4.4 days
Sertraline (Zoloft) half-life = 26 hours, 99% out of body in 5.4 days
Escitalopram (Lexapro) half-life = ~ 30 hours, 99% out of body in 6.1 days
Citalopram (Celexa) half-life = 36 hours, 99% out of body in 7.3 days
Fluoxetine (Prozac) half-life = 4 - 6 days, 99% out of body in 25 days
Norfluoxetine (the active metabolite of Prozac) half-life = 7 - 15 days
When it comes to the risk of withdrawal side-effects due to abrupt discontinuation of an antidepressant medication, Fluoxetine clearly has an advantage. On the other hand, if you needed to clear a medication out of someone's system quickly, Fluoxetine users would be at a disadvantage. If, for example, you wanted to start a new medication that could not be used safely together with an antidepressant medication, you would have to wait 5 whole weeks after stopping Fluoxetine before you could start the new medication. It takes that long for both the Fluoxetine and its active metabolite, Norfluoxetine, to be eliminated from the body.
Hope this information is helpful!