Thank you for your question. The half-life of Celexa is about 35 hours, meaning that it takes 35 hours for 50% of the drug in your body to be eliminated. Then in the next 35 hours, half of the. How Long Does Celexa Take To Leave Your System How long does it take citalopram to leave your system ? – Drugs.com I have been taking citalopram for the last six years. Celexa has a 36 hour half life.meaning it will take 36 hours for 50% of the drug to leave your system and another 36 hours for it to be fully out of your system. 90% of citalopram will be out of your system in about a week so it's safe to say within 2 weeks there will be insignificantly little to no citalopram in your body. this will leave your 5-ht reuptake pumps free for MDMA to work but like i said. your 5-ht receptors will most likely be downregulated for a lot longer. Factors That Influence How Long Citalopram (Celexa) Stays In Your System In comparison to other prescription drugs, Citalopram (Celexa) has a relatively short half-life, lasting around 35 hours. This means that, in most patients, it takes 35 hours after the initial consumption for the drug to be 50 percent cleared from the body provided another dose is not taken during this time. I would get off Celexa as soon as possible before your system is too used to it. I wouldn't think you need to take very long to taper down after only 6 days of use. Maybe try taking it every other day and see how you react, or cut the dose in half. Citalopram has a long half life of around 35 hours meaning it takes 35 hours for the body to clear 50% of the drug from your system. If you take the above factors into account it will take at least 7 days to clear the system. But it may take longer. Therefore, it might stay in your system as long as 250 hours depending on various factors. Doctors give trusted answers on uses, effects, side-effects, and cautions: Dr. Khanna on how long does celexa stay in your system: The half life of Clonazepam is as long as 50 hours. Citalopram has a long half life of around 35 hours meaning it takes 35 hours for the body to clear 50% of the drug from your system. If you take the above factors into account it will take at least 7 days to clear the system.