SSRI's Medications To Treat Depression
Today I'd like to talk to you about the use of selective serotonin reuptake inhibitors, or as they're more commonly known as SSRIs, and the treatment of depression.
First, let's talk a little bit about serotonin which is a hormone that's found in various parts of the body, not just the brain. It can be found in the digestive tract, the central nervous system, the pineal gland and blood platelet cells which are responsible for clotting.
In the brain, serotonin acts as a neurotransmitter and it transmits electrical impulses from one neuron to the next. This is the action of serotonin which has the greatest effect on moodl
There many ways that serotonin regulates the body and brain functioning. It can affect your mood, sleep, appetite, sexual desire and cognition. Changes in the level of serotonin can interfere with these functions and can lead to symptoms that we see in depression.
Role Of Serotonin in Depression
A decrease in serotonin as can call us depressive symptoms. The levels of serotonin can be reduced in a number of ways. There can be:
-a low production of serotonin and brain cells; a decrease in the number of receptor sites that bind serotonin on brain cells;
-an inability to bind properly to these receptor sites;
-a reduction in the storage of a precursor chemical, which is called tryptophan.
Tryptophan is used to make serotonin in brain cells the same way as it's used to make melatonin, which regulates our sleep/wake cycles.
How Do SSRI Work?
As you already know, one of the most widely used treatments for serotonin deficiency are the SSRI. Let's talk a little bit about how SSRIs work.
They bind to postsynaptic neurons and block the resorption of serotonin in the neurons synaptic region. This causes an increase in serotonin levels for that neuron. It allows for there to be more available serotonin binding in the postsynaptic cell receptor sites.
To make this point a little bit clearer let's look at the illustrate on this image. Here you can appreciate that in the highlighted region serotonin is produced in the cell and carried by vesicles to the nerve ending of the presynaptic cell. Then it's released into the synaptic region where it binds to receptor site and the postsynaptic nerve ending. This allows for the electrical impulses to be carried from the presynaptic nerve to the postsynaptic nerve. This is what regulates our bodily functions.
If there's a decrease of serotonin in the synaptic space, there's not going to be enough to bind to the receptor site in order to effectively transmit these impulses from one nerve to the next.
After the serotonin is done binding to a receptor sites, it's usually reabsorbed into back into the presynaptic nerve ending.
If the SSRIs are on board, they can block the resorption of serotonin back into the presynaptic nerve ending. This causes serotonin to stay in the synaptic region longer, which allows for more time to bind to the receptor sites, more time for the neural impulses to be transmitted and for normal following functions to occur.
Staying in the synaptic region longer allows serotonin to regulate the functions of the body more effectively, which can reduce the depressive symptoms.
Types Of SSRIs
There are different types of SSRIs there on the market today. They've been around since 1987 with the introduction of Prozac or Fluoxetine as it's known by its generic name.
There are also others like Paxil, Zoloft, Celexa and Lexapro. They are all now available in their generic forms.
I just like to note that in older adults we need to be a little more careful about prescribing antidepressants. We usually start with the very low doses for older adults and go very slow and increasing the dose until we get to a therapeutic dose.
We use Prozac and Paxil with caution in older adults for a few reasons. First, these two are metabolized in the liver in such a way that they can cause drug-drug interactions with many of the other drugs that older people take.
Secondly, Paxil can cause some slowing of a person's cognitive functioning, which happens more in older adults. It can also cause sedation, which can cause a fall risk for older adults. We try to use this very sparingly and older adults.
Celexa also has some cardiac side effects that can be related to very severe side effects such as palpitations, fainting or sudden death. There's been a limit on the dose range for selects and older adults that we try to use any more than 20 milligrams because these effects are seen at ranges above 20.
I'd also like to call your attention to another SSRI, Luvox. However, it's not used for the treatment of depression.
Common Side Effects Of SSRI's
There are many side effects that you see with SSRIs. I like to bring your attention to a few that also may be symptoms of depression such as headache, reduced libido, insomnia.
Patients may complain about these side effects after the initiation of an SSRI but it's important to ask the patient when the symptom actually started.
It can be a symptom of the depression that they're just not being aware of. They may blame on medication but it's actually more symptom of depression. It's very important to ask when did the symptoms start.
If a patient is having difficulty tolerating an SSRI because of the side effects involved and they don't go away after about a week, it's very important to alert the prescribing physician. The medication can either be reduced, adjusted it in some way or switched to a different medication.
The first line of activity would be to maybe switch to a different SSRI, because they don't all have the same side effects and would all affect the patient in the same way.
Interaction And Contraindications
Finally, I want to alert you to some of the contraindications or interactions that can occur with SSRIs. These antidepressants can increase the blood concentration of medications like warfarin, digoxin. These medications can be monitored in some aspects by lab tests, but some can't.
It's important to know that this interaction can occur, to just be mindful of it and to maybe reduce an SSRI dose if you see that it's interfering with another medication.
Patients with chronic pain, arthritis may use ibuprofen, naproxen on a more frequent basis, which can reduce the levels of SSRIs. The SSRI might need to be increased in these cases.
Lastly, certain agents like alcohol, diuretics, Ambien and other agents can increase SSRI levels. In these cases, we need to be aware because an increase of serotonin in the body can cause some mental status changes, hyperthermia, hypertension, different side effects that we need to be aware of. If that's the case, these medications need to be reduced.
The very high levels of serotonin in the body can produce something called a serotonin syndrome, which may lead to death in some patients. It is very important to monitor patients that have been put on these medications that are also using agents like diuretics and alcohol on a regular basis.