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Clonidine Half-Life & Full Clearance Time From System

clonidine in system

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Most people taking Catapres are unaware of how long it remains in their system. However, this is something all users should know, as the clonidine half-life can impact everything from having a drink with dinner to when it is safe to take other medications. Here is what users should know, from the half-life to clonidine and drug tests.

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Learn About Clonidine In System:

How Long Does Clonidine Stay In One’s System?

Knowing how long clonidine dose remains in the system is important for any user. Not only should those taking the medication be empowered in their knowledge, but sometimes, they will need to be able to safely time taking other substances with the drug.

Clonidine peak time is three to five hours after taking the medication orally; when injected or taken via a patch, peak time hits sooner. This is when the medication is at its most concentrated. Catapres half-life is reached at roughly 14 hours for most patients. This can extend to 33 hours in pediatric patients.

However, those with poor renal function may not reach clonidine plasma half-life—when the plasma concentration is at half of that seen at its peak—for 41 hours. As such, these individuals need to take extra care when starting medications or other substances that can interact with Catapres. Clonidine’s total body clearance (CL) is 219±92 mL/min on average, though it tends to be slower for women than for men.

It is important to note that the specifics on peak time, half-life, and full clearance can vary significantly between patients and even between routes of administration. As such, users worried about these aspects should consult with their doctor.

Factors That Impact How Long Clonidine Stays In The System

While there is plenty of data on how long Catapres stays in the system and its half-life, patients need to remember that the numbers given are averages, and their ability to clear the drug will vary. There are numerous factors that impact the half-life of clonidine and its full clearance from the body. These include:

  • the formula of the medication taken
  • the dose used
  • how often the medication was taken
  • the height and body mass of the user
  • how hydrated the patient is
  • the reason why it is taken (for example, someone taking clonidine for sleep is less likely to have struggles metabolizing it than someone with circulation problems)
  • if the user is physically active
  • the patient’s metabolic rate
  • problems with kidney function
  • drug and alcohol use
  • gender
  • other accompany medical conditions
Because there are so many factors at play, patients should not take general half-life and full elimination timelines as hard and fast rules. Always work directly with a doctor when there are concerns about Catapres interactions.

Does Clonidine Show Up On A Drug Test?

Drug testing for the clonidine class of drug is incredibly rare. However, there are tests that can detect it. Blood pressure medications are not common drugs of abuse, even when they have abuse potential. As such, most of the time, they will only be tested if there is a specific reason. For example, if abuse of Catapres is suspected, a doctor might order a clonidine drug test. Otherwise, users should not anticipate being screened for it.

Urine Test

Assuming that someone is being tested for clonidine presence, they can expect that their urine test will deliver a positive result if the medication has been taken in the last three days. Catapres has a total clearance of 177 mL/min and a renal clearance of 102 mL/min. A urine clonidine drug test is the most common test for the medication.

catapres drug test

Blood, Saliva, and Hair Tests

Clonidine drug test does not usually include blood, saliva, or hair screening. However, it is still possible in certain cases. This would typically occur if there is a specific reason for testing, and presence needs to be verified outside of the urine testing window. Patients should verify the details of testing with the lab in advance.

Clonidine And False Positives

With any medication, patients might worry about getting a false positive on a drug screening, especially if they must take them for employment. Clonidine drug test false positives are so rare as to be statistically insignificant. While other ADHD medications do cause false positives at a semi-high rate, because Catapres is not designed for ADHD treatment, it acts differently on the body.

Where there is greater concern regarding false results is in medical testing for types of cancers; specifically, pheochromocytoma and paragangliomas that secrete epinephrine, norepinephrine, or both. This is because Catapres can lower these chemicals in the body by as much as 50 percent. While the medication should be suppressed in advance of sample collection, this is not always done. Additionally, certain types of medications can prevent suppression, including β-adrenergic blockers, tricyclic antidepressants, and thiazide diuretics. For those who need frequent testing for epinephrine or norepinephrine presence, it might be best to consider clonidine alternatives.

Recovering From Clonidine Misuse

Not everyone who takes clonidine does so by following their doctor’s orders. Some abuse the medication. For those who are looking to stop use and live a sober life, drug rehab facilities are the place to start. These centers offer a wide range of substance abuse treatment options to meet the needs of every patient.

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  1. Catapres® (clonidine hydrochloride, USP). Boehringer Ingelheim International. 2009.
  2. Basker S, Singh G, Jacob R. Clonidine in paediatrics – a review. Indian Journal of Anaesthesia. 2009; 53(3): 270–280.
  3. Sullivan PA, De Quattro V, Foti A, Curzon G. Effects of clonidine on central and peripheral nerve tone in primary hypertension. Hypertension. 1986; 8(7): 611-7.
Isaak Stotts

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.


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