Long QT syndrome (LQTS) is a condition in which repolarization of the heart after a heartbeat is affected. It results in an increased risk of an irregular heartbeat which can result in fainting, drowning, seizures, or sudden death. Some people are born with a genetic mutation that causes long QT syndrome (congenital long QT syndrome). Long QT syndrome may also be caused by certain medications, mineral imbalances, or medical conditions (acquired long QT syndrome).
Many commonly used drugs can prolong the QT interval, especially if used in combination with other substances which affect their metabolism. Prolongation of the QT interval can cause life-threatening polymorphic ventricular tachycardia also known as torsade de pointes. Women and certain susceptible people are more prone to prolongation of the QT interval. This predisposition could be congenital or due to conditions such as hypokalaemia, hypomagnesaemia, renal failure or cardiac failure. Susceptible patients need an electrocardiogram before and after starting drugs that can prolong the QT interval. If a drug prolongs the QT interval beyond normal limits, the benefits of continuing the drug should be weighed against the relatively rare risk of potentially life-threatening arrhythmias.
What is Prozac?
Prozac is an antidepressant. It is mainly used to treat major depression, obsessive-compulsive disorder, and panic disorder. Also known by its generic name, fluoxetine, Prozac is a selective serotonin reuptake inhibitor (SSRI). Around 1 in 10 people in the United States (U.S.) are thought to use SSRI drugs, and 1 in 4 women in their 40s and 50s.
Prozac first appeared in the U.S. in 1988 and it became one of the most widely prescribed antidepressants in the country. It remains popular, although newer drugs are now available, such as sertraline and citalopram.
It is available as a liquid, tablet, capsule, and as a delayed-release, long-acting capsule. It is suitable for adults and it can be used in some cases for children over the age of 10 years.
How Prozac works
Prozac is in a class of medications called selective serotonin reuptake inhibitors (SSRIs). It works by increasing the amount of serotonin, a natural substance in the brain that helps maintain mental balance.
People taking Prozac may see an improvement in their symptoms after 1 to 2 weeks, although it usually takes between 4 and 6 weeks before patients feel the full benefits. That’s because it takes around a week for fluoxetine levels to build up in the body, and then a few weeks longer for the body to adapt and get used to it.
Other symptoms related to low serotonin levels, like the disruption of normal sleep patterns or loss of appetite, can also show marked improvement within a few weeks. Such physical improvements are usually a good sign that the medication is working as hoped. The reason it takes some time for anti-depressants like Prozac to work is that they need to build up in the body.
Can Prozac cause QT prolongation?
Yes, a study published in the British Journal of Pharmacology reported that Prozac can cause QT interval prolongation and arrhythmias. The potential for QT prolongation to occur should be considered as part of the risk-benefit assessment prior to prescribing antidepressants like Prozac.
People taking Prozac should also avoid grapefruit juice because it can increase the risk of QT prolongation by inhibiting the metabolism of the drug. Women are more susceptible than men to Prozac-induced QT prolongation. Renal failure, cardiac failure, and hepatic failure are also risk factors.
Fluoxetine oral capsules have boxed warnings. A boxed warning is a serious warning from the Food and Drug Administration (FDA).
Risk of suicidal thoughts and behaviors in certain people. Like other drugs used to treat depression, fluoxetine may increase the risk of suicidal thoughts and behaviors. Specifically, the drug may increase this risk in people ages 24 years and younger. This side effect is more likely to occur when you first start taking the medication and any time your doctor adjusts your dosage.
In studies, antidepressant use didn’t increase the risk of suicidal thoughts and behaviors in people older than age 24 years. And in people ages 65 years and older, these drugs actually decreased this risk.
What other side effects can Prozac cause?
Mild side effects of Prozac that have been reported include:
• diarrhea
• dry mouth
• feeling anxious
• fatigue (having less energy than usual)
• hot flashes
• indigestion
• loss of appetite
• nausea or vomiting
• sexual side effects*
• sweating more than usual
• swelling or irritation in your throat and nasal cavity
• tremors
• unusual dreams
• weakness
Mild side effects of many drugs may go away within a few days or a couple of weeks. But if they become bothersome, talk with your doctor or pharmacist..
Serious side effects
Serious side effects from Prozac can occur, but they aren’t common. If you have serious side effects from fluoxetine oral capsules, call your doctor right away. But if you think you’re having a medical emergency, you should call 911 or your local emergency number.
Serious side effects of Prozac that have been reported include:
• trouble sleeping
• abnormal or heavy bleeding
• low sodium level
• serotonin syndrome (a condition in which you have a buildup of the brain chemical serotonin in your body)
• weight loss*
• allergic reaction*
Prozac may decrease appetite and cause weight loss in children. Your child’s doctor will watch his or her growth carefully. Talk to your child’s doctor if you have concerns about your child’s growth or weight while he or she is taking this medication. Talk to your child’s doctor about the risks of giving Prozac to your child.
Prozac may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.
If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).
