Celexa (Citalopram): Mechanism of action, Overdose symptoms, Cautions

Celexa (citalopram hydrobromide), the generic name of which is Citalopram, is an antidepressant drug that belongs to selective serotonin reuptake inhibitors (SSRI) with a chemical configuration unlike other SSRIs or of tri/tetracyclic, or other existing antidepressant agents.

Citalopram`s molecular formula is C₂₀H₂₂BrFN₂O.

Uses

Celexa (citalopram) is approved to treat the following conditions:

• major depression
• depressive attacks and panic disorders, with or without agoraphobia (in selected countries)
• obsessive-compulsive disorder (in selected countries)

Mechanism of action

The human brain functions through the use of special elements called neurotransmitters, also known as serotonin and norepinephrine. These neurotransmitters convey signals between nerve cells. Research indicates that anomalies in neurotransmitter activity can influence behavior and mood. Although low levels of norepinephrine and serotonin do not necessarily trigger depression, it is broadly believed that increase of these chemicals is correlated with mood improvements in depressed people.

All drugs in selective serotonin reuptake inhibitor class have the same universal mechanism of action. SSRIs appear to ease symptoms of depression by hindering the reuptake (reabsorption) of serotonin by specific nerve cells in human brain. In this way, more serotonin is left available, which augments neurotransmission and elevates the mood. SSRIs are designated as selective since they appear to affect serotonin considerably more when compared to other neurotransmitters. Accordingly, these drugs work by permitting the brain to extract the best use of the decreased amounts of serotonin, which is available at the time. Eventually, the levels serotonin that is produced by the body might normalize, and in some cases, the SSRI can be cut down or altogether withdrawn.

SSRI antidepressants are known to be at least ten times more selective for inhibiting the serotonin reuptake as opposed to norepinephrine reuptake. Yet, SSRIs vary in their selectivity and effectiveness in inhibiting serotonin reuptake and several of them can significantly impact other receptors and transporters in the brain.

The most popular SSRI drugs are:

• Celexa (citalopram)
• Lexapro (escitalopram)
• Prozac (fluoxetine)
• Paxil (paroxetine)
• Zoloft (sertraline)

Each SSRI drug has a unique list of various pharmacologic actions. This explains the differentiation in their tolerability and effectiveness.

Half-life as SSRI differentiator

The half-life of a drug is the time interval needed to reach steady-state plasma concentrations. It can be used to determine the approximate time after which the drug will be eliminated from the body if treatment is stopped.

Celexa has a shorter half-life of 20-35 hours (as opposed to 50-75 hours for other SSRIs). Thus the steady-state concentrations (and therapeutic effect) are achieved much faster.

Antidepressants with comparatively short half-lives are appropriate for patients with multiple co-morbidities and multiple-drug regimens since they can be taken once per day. A shorter half-life allows physicians to shift more quickly to another antidepressant drug if the treatment fails or if undesirable drug effects occur.

Celexa vs Other SSRIs

Celexa vs. Zoloft

Both Celexa and Zoloft have the lowest likelihood of enzyme inhibition, which marks them the optimal SSRIs for patients who are at risk of drug interactions.

Zoloft (sertraline) has a wider range of licensed indications, when compared to Celexa, that include major depressive disorder, PTSD, panic disorder, obsessive-compulsive disorder, a premenstrual dysphoric disorder in adults. The newest indication is the social anxiety disorder.

Zoloft may be the finest choice when beginning treatment for moderate or severe major depression because of its favorable balance between benefits, side effects, and price.

Zoloft is more likely to trigger insomnia and diarrhea than Celexa.

Unlike Celexa, Zoloft is not to be taken with diuretic medications.

Celexa vs. Lexapro

Lexapro (escitalopram) acts a bit quicker than Celexa, and it’s a good choice when the doctor wants to achieve a rapid antidepressant response.

Lexapro (escitalopram) may be better in effectiveness compared with Celexa for treating major depressive disorder.

Lexapro as the newest generation drug in the SSRIs class is also the most expensive SSRI medicine.

Celexa vs. Prozac

Prozac (fluoxetine) begins acting more slowly when compared to Celexa. Therefore, Prozac is the best SSRI for patients with poor compliance or those who are prone to interrupting treatment or missing doses.

Prozac is a more activating SSRI than Celexa, and it shouldn’t be used by patients prone to agitation.

Doses

All feasible dosages of Celexa may not be described here. The dosage and frequency of treatment depend on:

• the age of a person
• the condition being treated
• the severity of your condition
• the reaction to the first dose
• other health conditions that the patient might have

The initial dose is 20 mg split into two parts. The dose might be increased up to 40 mg per day after a week. It should be noted that 60 mg does not deliver more effectiveness than 40 mg. It usually takes several weeks of treatment before the full effects are felt by the patient. Doses are frequently gradually adjusted uphill to find the best dose.

Adult dosage (18–60 years)

• The initial dose is 20 mg.
• Your doctor might recommend an increase in dosage. Doses can be increased only once per week.
• The maximum dose is 40 mg. Higher doses are unnecessary and increase the risk of QT prolongation.

Child dosage (0–17 years)

Celexa is effective and safe for use in children below the age of 18.

Senior dosage (61+ years)

20 mg once daily is the maximum dose. The kidneys of senior adults don’t work as well as they used to, which means it can take your body longer to process medications. Consequently, the drug is eliminated much slower. This escalates your risk of side effects.

Special considerations

• Cytochrome P450 2C19 poor metabolizers: do not take over 20 mg of Celexa once daily.
• People with liver disease: do not take over 20 mg of Celexa daily. The levels of Celexa in your body might increase and cause more side effects in liver disease patients.

Missed dose

Take a missed dose as soon as you remember. Skip the missed dose and continue your usual schedule if it is about the time of the next dose. You do not need to double the dose to catch up with effective dose.

Overdose

If you take too much Celexa, you may develop symptoms of serotonin syndrome, including:

• agitation
• hallucinations
• fever
• diarrhea
• nausea
• confusion
• coordination troubles
• muscle rigidity
• muscle trembling
• speeding heartbeat
• sweating
• vomiting
• coma

If any of these symptoms occur, seek help at the nearest emergency department.

Withdrawal symptoms

You shouldn’t stop taking Celexa without consulting your doctor first. Stopping Celexa too swiftly can produce serious symptoms such as high or low mood, headache, anxiety, feeling restless, irritability, changes in sleep habits, perspiring, nausea, faintness, electric shock-like feelings, or confusion. The doctor may recommend lowering the dose gradually as it can be harmful to stop taking medications abruptly.

Storing conditions

Store Celexa at room temperature in a dry, dark place. The storage place must be inaccessible to children and pets. Do not pour citalopram into a drain or flush it down the toilet.

Side Effects

The side effects in adults for Celexa differ from the side effects in children.

If these effects are minor, they might disappear within a couple of weeks. If the effects are more severe, you should consult your pharmacist or doctor.

Serious side effects

Get in touch with your doctor immediately if serious side effects manifest themselves.

These effects (and their symptoms) may include:

Sexual side effects

In both men and women, sexual side effects are usual with antidepressants, so your concern is reasonable.

Undesired consequences for your sexual function can include:

• a change in your sex drive
• problems with arousal, comfort and satisfaction
• erectile problems
• orgasm problems

Celexa, as an antidepressant drug of SSRI type, is rather likely to cause sexual side effects (the probability is around 72%). For some patients, sexual side effects are insignificant or may disappear as their bodies adjust to citalopram. For others, sexual side effects may remain a problem.

Your doctor may suggest one of these strategies:

• Waiting some weeks to see whether sexual side effects disappear.
• Engaging in sexual activity prior to your daily intake of Celexa.
• Modifying the dose of Celexa to lower the risk of sexual side effects.
• Transferring to another antidepressant that is less likely to instigate sexual side effects.
• Adding a drug that improves sexual function, such as sildenafil (Viagra), tadalafil (Cialis) or vardenafil (Levitra).

Discontinuing medication because of sexual side effects is not an unusual problem, and for most patients this means depression reappears. Work with your physician to find an efficient antidepressant or combination of drugs that will ease your sexual side effects while managing your depression.

Celexa and weight gain

There is research showing that anyone taking SSRIs like Celexa for a 6 to 12 months is likely to gain some weight.

Why Celexa causes weight gain

There hasn’t been much academic research carried out as to why antidepressants in general – and SSRIs in particular – make people prone to gaining weight. Most patients were told in the past that Celexa wouldn't produce any weight gain. However, according to new information it probably will, but most medical experts don’t understand why.

Below are some theories of how Celexa can drive weight gain:

• Appetite increase
• Carbohydrate cravings
• Body’s fat storage
• Drug interactions (in patients with slower metabolism)
• Hormonal abnormalities
• Improved taste
• Motivation deficit
• Side effects (becoming lazier than usual, sleepy, not engaging in physical activity)

Factors influencing weight gain on Celexa

How much weight can I gain from Celexa?

Among other SSRIs, Celexa appears to be the least likely to produce weight gain, according to some recent studies. You can realistically expect an average weight gain of 10 lbs over the course of Celexa treatment (after taking the drug for over 6 months).

Will everyone gain weight while on Celexa?

Those patients taking add-on treatments, such as stimulants increasing activity in the CNS, may gain no weight. Other patients who take especially astute care of their diet and exercise routine may not have trouble with the extra pound. Some studies indicate that 25% of patients taking SSRI antidepressants will gain weight.

Celexa and weight loss

Interestingly, some patients reported losing weight while on Celexa. It is not clear why Celexa triggers weight loss; one explanation is related to side effects such as nausea, diarrhea, and loss of appetite. A second possible explanation is citalopram may enable some overweight patients to regain energy and re-discover motivation to exercise and stay away from emotional eating.

Precautions

Drug Interactions

Medicines that might interact with Celexa include:

1. Serotonin-enhancing drugs

A potentially lethal condition called serotonin syndrome may ensue when Celexa (citalopram) is taken with other medicines, which can boost serotonin levels in human body. Also, this may occur after an increase in dosage.

2. Drugs affecting heart rhythm

Do not take Celexa with drugs that affect your heart rhythm. Taking both Celexa and these drugs may boost your risk of arrhythmia.

3. Bleeding risk enhancing drugs

Celexa might boost your risk of bruising or bleeding, especially if you’re also taking other drugs increasing bleeding risk.

4. Tricyclic antidepressants (TCAs)

Caution should be applied when taking Celexa with TCAs. This increases the levels of the TCA in your body and correspondingly higher risk of side effects.

5. Drugs that cause drowsiness or sedation

Taking Celexa may boost the effects of medicines causing sedation.

6. Inhibitors of Cytochrome P450 2C19

Cytochrome P450 2C19 is a protein that helps to break down drugs, including Celexa. Some medicines are known to inhibit or slow down, the actions of this protein. When Celexa and drugs slowing down the actions of Cytochrome P450 2C19 are taken at the same time, it can result in the excessive amount of citalopram in the human body.

Celexa and alcohol

Don’t drink alcohol when taking Celexa. Citalopram can result in increased sleepiness. It can disturb your ability to think clearly, make decisions, or react quickly. Alcohol consumption can boost these effects.