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How Long Does Buspar Stay In Your System And Its Mechanism Of Action

Last Updated: June 17, 2022

Authored by Isaak Stotts, LP

Reviewed by Michael Espelin APRN

Buspirone, brand name Buspar, is used as an anxiolytic agent prescribed regularly for generalized anxiety disorder. Does Buspirone work immediately? It is not suitable for use if one requires immediate effect, this is why doctors prescribe its use for a long duration. So, how does Buspirone work? Patients have to take them over weeks for them to work properly. Although it is not a controlled substance and is deemed generally safe, one may wonder if it can stay in the system long enough to cause problems on a drug test. Buspar half-life is relatively short which means it leaves the system quickly rendering it safe to use. Though Buspirone leaves the system quite rapidly, its metabolites can be found in different body systems for a certain period.

Buspirone Mechanism of Action

Buspirone mechanism of action has yet to be fully understood. It has been established, however, that it has neither anticonvulsant nor muscle relaxant properties. Nonetheless, it has mildly sedating properties this is why it is used as an anxiolytic, making Buspar relatively safe during pregnancy. How does Buspirone work? Does Buspar affect serotonin? Based on the product information, Buspar exhibits a high affinity for serotonin receptors. More specifically, it demonstrates a high affinity for serotonin 5HT1A receptors and a weak affinity for 5HT2 receptors. The medicine stimulates the activity of 5ht1a and 5ht2 receptors. As a result, serotonin levels are regulated and anxiety and its symptoms are alleviated. About 90% of the Buspar dosage taken is readily absorbed by the body through the blood, approximately 40 to 90 minutes following intake. Although, it may take several weeks before positive clinical results become apparent. The delayed Buspirone mechanism of action is due to the adaptation of the 5HT1A receptors. One cannot speed up the adaptation of the body to the drug by a deliberate dose increment. Any modifications to the treatment routine may cause adverse reactions, such as for example Buspar sexual side effects.

Does Buspirone Work Immediately?

Buspirone is used as an anxiolytic agent, but how long does Buspar take to work? Buspar doesn’t work immediately. It takes anywhere from 3-4 weeks for it to start showing its effect. One has to take it every day for at least 14 days with good compliance to keep a certain level of medicine in the system to feel any better. If the patient is looking for immediate management or has low compliance to medication, they can contact their health care provider for a better alternative to Buspirone for their anxiety management.

A doctor makes tests how long buspar stays in the system.

How Long Does Buspar Stay In Your System?

We know how long does Buspar take to work but how long does Buspar stay in your system once it has started working? Buspirone has a relatively short half-life and it gets degraded quickly in the system. According to the half-life of Buspar, it can stay anywhere from 24 to 48 hours in the system depending on the dose, previous medical condition, and metabolic status of the body. It gets eliminated in urine, saliva and may get absorbed in the hair where it is broken down by different enzymatic actions.

How Long Does It Stay In Urine?

In a general drug screening, it is not detected in urine because of a lack of specifically aimed tests for buspirone. However, By special testing methods, it can be detected in urine for up to 24 to 36 hours. In the meantime within 24 hours, 62% of metabolites get eliminated in the urine as a by-product. This duration is non-specific and can be challenged in case of renal impairment or any other metabolic abnormality.

How Long Does It Stay In Blood?

Buspar has a relatively short half-life. It is rapidly absorbed in the system despite having a delayed effect, it can be detected in blood shortly after administration. After the first dose of drugs it can be detected in blood in 18-24 hours. This duration varies for each individual person, dose, medical condition, hepatic or renal impairment, and type of test used to detect the drug in the blood.

How Long Does It Stay In Saliva?

Buspar stays in saliva for 24 hours after the last dose given the normal circumstances and no previous medical conditions. It is rapidly absorbed and excreted in the saliva of the patient. It starts appearing in saliva after an hour of the initial dose and may stay there if the maintenance dose of drugs is given to the patient. It can be detected for 24 hours after the last oral dose.

How Long Does It Stay In Hair?

There are no studies stating the exact duration for which it can be detected in hair. As a general rule, drugs stay the longest in hair follicles. Some sources state that It may take up to 90 days for drugs to clear out of the hair but no scientific evidence supports this.

Buspar Half-Life

According to FDA data, the Buspar half-life after a single dose of 10mg to 40mg is 2-3 hours. It has a relatively short half-life as it has extensive first-pass metabolism. It is rapidly absorbed, metabolized in the liver, and reaches its peak plasma concentration in an hour. However, several factors can influence the half-life of Buspirone, such as for instance Buspirone interactions with other drugs or alcohol. Furthermore, Buspirone is metabolized by the liver and excreted by the kidneys, so any damage to either of these organs can prolong the half-life (the extent depends on the individual case), and may cause some Buspar withdrawal symptoms. This is why Buspirone is not recommended for patients with impaired renal or hepatic function. It has been discovered that people living with these health conditions may experience increased plasma levels and a prolonged Buspirone half-life in the body.

Does Buspirone Show Up On Drug Tests?

Naturally, one might wonder if there are special drug tests for Buspirone and its metabolites. The answer is – no. First of all, this medicine is not a controlled one. It does not show the same psychological and physical addiction potential as other controlled substances. It is considered relatively safe if taken in recommended doses and according to medical advice.  Secondly, it is not included in standard drug tests (5-12 panel tests). It requires special testing kits which should be directed toward the drug in order to get detected. As it is not a controlled substance, a special screening for Buspirone is hardly ever done even in military recruits. At the same time, there is an increasing concern that Buspirone may show up as benzos or one of its metabolites. As of now, no evidence would support this claim.

Factors Affecting How Long Buspar Stays In The System

How long Buspar stays in the system depends on various factors. It is metabolized in the liver showing extensive first-pass metabolism. The initial concentration of the drug in the system depends on the dose of the drug and the time for which one is taking Buspar.

Other Factors Which Can Affect the Time Duration of the Drug in the System Are:

  • age of the patient
  • dose of the drug
  • the weight of the patient
  • any metabolic impairment
  • hepatic or renal dysfunction
  • Previous medical condition
  • Race
  • Genetics

Hepatic or renal impairment can delay its elimination leading to the accumulation of drugs in the system and prolonged effects.  Genetic causes can impair the metabolism of the drug due to alteration of enzymatic activity in different races and individuals. Can Buspirone cause weight gain? The answer would also be yes.

How To Get Buspar Out Of The System Safely?

With a relatively short Buspar half-life, Buspirone is a medication that doesn’t alter the result of the screening to cause any trouble. Besides, the possibility of the false-positive on Buspar is close to zero. If one wants to make sure to get the Buspar of their symptoms, tapering dose until clinical testing comes back negative is the best way to do this.

Even though Buspar’s addictive properties are very weak, yet the probability of medication abuse is still present. Buspar common side effects like relaxation and sedation are primary reasons for abuse. If a close or a loved one is suspected of abusing the drug, it is time to get information and contact a local drug rehabilitation facility. There, a patient will undergo either a long-term or short-term drug rehabilitation program. These programs are usually multi-staged and include not only the initial detox but also physical and psychological treatment. The idea of such a treatment is to identify the initial cause of the problem, resolve the issue, and provide supportive therapy afterward.

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Page Sources

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Published on: July 10th, 2020

Updated on: June 17th, 2022

About Author

Isaak Stotts, LP

Isaak Stotts is an in-house medical writer in AddictionResource. Isaak learned addiction psychology at Aspen University and got a Master's Degree in Arts in Psychology and Addiction Counseling. After graduation, he became a substance abuse counselor, providing individual, group, and family counseling for those who strive to achieve and maintain sobriety and recovery goals.

Medically Reviewed by

Michael Espelin APRN

8 years of nursing experience in wide variety of behavioral and addition settings that include adult inpatient and outpatient mental health services with substance use disorders, and geriatric long-term care and hospice care.  He has a particular interest in psychopharmacology, nutritional psychiatry, and alternative treatment options involving particular vitamins, dietary supplements, and administering auricular acupuncture.