Modern psychopharmacology is largely the story of chemical neurotransmission

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  Concept of Citalopram's half-life Citalopram has a half-life of approximately 36 hours. This means that after taking a dose of citalopram, the amount of the drug in your bloodstream will decrease by half every 36 hours. It takes approximately 5 half-lives for a drug to reach steady state. Steady state is the point where the amount of drug entering your body is equal to the amount of drug leaving your body. In the case of citalopram, it would take approximately 5 half-lives, or 180 hours, for the drug to reach steady state. How frequently should citalopram be dosed based on its half-life? Citalopram is typically dosed once daily. This is because the drug has a long half-life and remains in your bloodstream for a long time. Dosing citalopram once daily is sufficient to maintain a steady state concentration of the drug in your bloodstream. Example Let's say you start taking a 20 mg dose of citalopram once daily. After 36 hours, the amount of citalopram in your bloodstream will be 10 mg. After another 36 hours, the amount of citalopram in your bloodstream will be 5 mg. And so on. After 180 hours, the amount of citalopram in your bloodstream will be 0.625 mg. This is the point where citalopram has reached steady state. At steady state, the amount of citalopram entering your body each day is equal to the amount of citalopram leaving your body each day. This means that you can continue to take a 20 mg dose of citalopram once daily and your blood concentration of the drug will remain stable. Conclusion Citalopram is an SSRI antidepressant that is approved by the FDA for the treatment of major depressive disorder and generalized anxiety disorder. Citalopram has a half-life of approximately 36 hours and it takes approximately 5 half-lives for the drug to reach steady state. Citalopram is typically dosed once daily to maintain a steady state concentration of the drug in the bloodstream.  

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FDA-approved medication currently used in psychiatry: Citalopram

Citalopram is a selective serotonin reuptake inhibitor (SSRI) antidepressant that is approved by the FDA for the treatment of major depressive disorder and generalized anxiety disorder.