Effexor Half-Life: How Long Venlafaxine Stays In System

Last Updated: December 19, 2019

Authored by Nena Messina, Ph.D.

Individual factors such as age, genetics, liver and renal function, and dosing play a critical role in how long Effexor stays in the system. There is a difference in Effexor drug half-lives of immediate-release and extended-release formulations. It’s highly recommended not to start taking venlafaxine without proper consultation of a health-care provider. Use this medication due to prescription recommendations to avoid severe health damage.

How Long Does Effexor Stay In System?

How long does it take for Effexor to get out of the system?

The immediate-release elimination venlafaxine half-life is about 5 ± 2 hours, while elimination half-life of Effexor XR  is about 10.7 ± 3.2 hours.

How many days should pass to a drug leave a system completely after stopping it?

Some patients may excrete the medication in just 16.5 hours, while it may take 1.6 days for others to completely excrete it.

Will venlafaxine show on a drug test?

Effexor drug tests fall basically into two categories, screening tests, and confirmatory tests. Due to the lack of specificity of the screening tests for this drug, confirmatory tests will distinguish venlafaxine from other medications.

effexor urine drug test

Time Of Staying In Urine

Effexor may show up on a urine drug test after 48 hours of its administration. Effexor false-positive urine immunoassay screening tests for phencyclidine and amphetamine have been reported. This is due to the lack of specificity of the screening tests. False-positive test results may be expected for several days following venlafaxine stopping. Gas chromatography and mass spectrometry are confirmatory Effexor drug tests that will distinguish venlafaxine from phencyclidine.

Time Of Staying In Blood

Steady-state concentrations of venlafaxine in plasma are attained within 3 days of oral multiple-dose therapy. As a result, blood samples may be collected within 72 hours for the estimation of venlafaxine.

Time Of Staying In Hair

According to a study published in the US National Library of Medicine, these antidepressant drugs can be detected in the hair follicle for at least 16 months after intake. As a result, venlafaxine also may be detected after about 1.5 years of its intake.

Factors Influencing Time Of Venlafaxine Stay In System

Individual Features

Individual factors play a crucial role in how long Effexor XR lasts in the system. Two persons may not clear Effexor at the same time.

  • Patient Age. There are several age-related factors that may prolong venlafaxine excretion time. The elderly with restricted hepatic blood flow and decreased kidney functions may have a prolonged excretion of the drug. The elimination half-life of venlafaxine is longer in neonates than adults, ranging between 12 and 15 hours. The steady-state venlafaxine half-life is increased in the elderly than the younger persons by 24%.
  • Patient’s Body Mass And Fats. A person’s body mass and fat percentage may affect medication metabolism and excretion. The persons with a small body mass who take venlafaxine may excrete it slowly as they ingested a greater quantity of the medication relative to the size of their systems. On the other hand, the one with greater body mass may excrete it quickly.
  • Genetics. Effexor mechanism of action and its metabolism and excretion may be affected by genetic variations. A patient with poor medication metabolism always has prolonged clearance time. According to the National Center for Biotechnology Information, patients who carry two inactive copies of CYP2D6 “poor metabolizers” may have decreased capacity for metabolization of Effexor, leading in less active metabolites in their body. On the other hand, those who carry more than two copies of functional CYP2D6 alleles “ultrarapid metabolizers” may have an increased capacity for its metabolism, leading in more active metabolites in their bodies.
  • Food. It is recommended to take this medication with food. According to the US National Library of Medicine, food decreases the rate of absorption of venlafaxine tablets, with no effect on the extent of absorption.
  • Renal And Hepatic Functions. The elimination half-life of Effexor is usually prolonged in patients with liver problems. A patient with hepatic fibrosis or cirrhosis generally retains the medication in the body more than those with normal hepatic functions. Moreover, patients with renal impairment problems may retain about 55% more of the dose than those with normal kidney functions.
  • PH Of Urine. A low PH of urine (acidic urine) will accelerate the excretion of the drug out of the system, while high PH of urine (alkaline urine) would help in venlafaxine reabsorption from urinary bladder into the blood again. As a result, alkaline urine would retain the medication in the body more than acidic urine.

Dose Taken

A patient who takes low doses of the medication would metabolize and excrete it quickly. For instance, patients who take a dose of venlafaxine tablets at 37.5 mg daily would likely metabolize and excrete it faster than those who take a dose of venlafaxine ER 150mg capsules mg daily.

Mixing With Other Drugs

Mixing Effexor with other medications may cause an increase or decrease in venlafaxine concentration in the blood. Dangerous venlafaxine drug interactions occur when a person mixes it with CYP2D6 enzyme inhibitors such as Fluoxetine, Paxil, and bupropion. Mixing together can prolong the clearance time of venlafaxine as enzyme inhibitors decrease its metabolism and excretion. Mixing CYP2D6 enzyme inducers such as Haloperidol, Glutethimide, and Rifampin with Effexor can decrease its concentration in the blood as these medications accelerate venlafaxine metabolism and excretion. As a result, the therapeutic efficacy of venlafaxine was decreased when it was mixed with CYP2D6 inducer.

effexor staying in system

Frequency Of Use

High frequency of venlafaxine use at greater than recommended doses may increase drug concentration in the body. Therefore, the side effects of Effexor may appear. On the other hand, those who take Effexor irregularly or intermittently are less likely to attain peak concentration of the drug throughout the system. In this case, the drug may be ineffective in treating depression.

Venlafaxine Absorption And Metabolization

The Effexor drug class is SNRI. It is taken orally and absorbed from the gastrointestinal tract into the bloodstream. The sustained-release Effexor tablet is more slowly absorbed than immediate-release venlafaxine tablets. About 92% of the Effexor dose is absorbed orally.

Effexor and its metabolites are primarily excreted via the kidneys. The drug is excreted as 5% unchanged venlafaxine, 55% O-desmethylvenlafaxine, and 27% other minor inactive metabolites.

Clear Effexor From System Safely

There are several natural ways to speed up the Effexor clearance from the body safely: 

  • Drinking plenty of water would increase urine flow. Increasing the urinary flow rate would excrete the medication out of the body faster.
  • Changing the PH of the urine to be acidic would excrete the medication quickly. The urine could be acidic by drinking lemon juice or taking vitamin c.
  • Using CYP2D6 inducers would reduce the half-life of the drug and quickly excrete the drug in the urine. The use of enzyme inducers should be done under medical supervision.

If there is a need to stop the Effexor use, a doctor may also consider the difference between Prozac and Effexor or other drugs for anxiety and depression to choose an alternative medication.

An Effexor addiction may occur when a person continues to misuse a drug. Treating addiction to the Effexor as soon as possible will help to get rid of adverse health complications. Do not hesitate to find a rehab for drug addicts and start specialized treatment with the support of medical professionals.

Page Sources

  1. SUPPLEMENT APPROVAL. Food and Drug Administration. https://www.accessdata.fda.gov/drugsatfda_docs/appletter/2012/020151s059,020699s100ltr.pdf.
  2. Jain RT, Panda J, Srivastava A. Two Formulations of Venlafaxine are Bioequivalent when Administered as Open Capsule Mixed with Applesauce to Healthy Subjects. Indian Journal of Pharmaceutical Sciences. 2011; 73(5): 510–516. doi:10.4103/0250-474X.98989. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3425062/.
  3. Troy SM, Schultz RW, Parker VD, Chiang ST, Blum RA. The effect of renal disease on the disposition of venlafaxine. Clinical Pharmacology & Therapeutics. 1994; 56(1): 14-21. https://www.ncbi.nlm.nih.gov/pubmed/8033490.
  4. Shen M, Xiang P, Wu H, Shen B, Huang Z. Detection of antidepressant and antipsychotic drugs in human hair. Forensic Science International. 2002; 126(2): 153-61. https://www.ncbi.nlm.nih.gov/pubmed/12084493.
  5. Boucher N1, Koren G, Beaulac-Baillargeon L. Maternal use of venlafaxine near term: correlation between neonatal effects and plasma concentrations. Therapeutic Drug Monitoring. 2009; 31(3): 404-9. doi: 10.1097/FTD.0b013e3181a58fb4. https://www.ncbi.nlm.nih.gov/pubmed/19455083.
  6. Klamerus KJ1, Parker VD, Rudolph RL, Derivan AT, Chiang ST. Effects of age and gender on venlafaxine and O-desmethylvenlafaxine pharmacokinetics. Pharmacotherapy. 1996; 16(5): 915-23. https://www.ncbi.nlm.nih.gov/pubmed/8888087.
  7. Dean L. Venlafaxine Therapy and CYP2D6 Genotype. 2015 Jul 27. In: Pratt V, McLeod H, Rubinstein W, et al., editors. Medical Genetics Summaries. Bethesda (MD): National Center for Biotechnology Information (US). https://www.ncbi.nlm.nih.gov/books/NBK305561/.
  8. Troy SM1, Parker VP, Hicks DR, Pollack GM, Chiang ST. Pharmacokinetics and effect of food on the bioavailability of orally administered venlafaxine. The Journal of Clinical Pharmacology. 1997; 37(10): 954-61. https://www.ncbi.nlm.nih.gov/pubmed/9505987.
  9. Venlafaxine. U.S. National Library of Medicine. https://pubchem.ncbi.nlm.nih.gov/compound/venlafaxine#section=Information-Sources.

Published on: November 29th, 2019

Updated on: December 19th, 2019

About Author

Nena Messina, Ph.D.

Nena Messina is a specialist in drug-related domestic violence. She devoted her life to the study of the connection between crime, mental health, and substance abuse. Apart from her work as management at addiction center, Nena regularly takes part in the educational program as a lecturer.


Leave a comment