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How Long Does It Take for Klonopin to Kick In?

In most cases, Klonopin should take about 1 to 4 hours to work when taken as prescribed. The effects may last for up to 12 hours.

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You should never take more of your Klonopin or take it in a different way than intended by your doctor to try to speed up the onset of effects. Doing so can increase your risk of complications and overdose and may cause the medication to work differently than intended.

How Klonopin’s Half-Life Affects the Onset of Effects

Klonopin is a brand name for the intermediate-acting benzodiazepine, clonazepam. These drugs are prescribed to treat seizure disorders and also treat panic attacks by decreasing activity in the brain. (1)

Klonopin has a half-life of about 30 to 40 hours, which is how long it takes the body to eliminate around 50 percent of the drug.

Within about four to five half-lives, or 120 to 200 hours, you can expect at least 95 percent of the drug to be eliminated from the body, assuming the body is able to process the drug normally. (2)

Klonopin’s half-life is relevant to how long it takes clonazepam to work because the longer the half-life, the longer it’ll take for this benzo to start working and producing calming effects.

Klonopin is often called a long-acting benzodiazepine but in reality, the term intermediate-acting is arguably more accurate. (3)

Klonopin has a half-life of about 30 to 40 hours, which is how long it takes the body to eliminate around 50 percent of the drug.

Klonopin is often called a long-acting benzodiazepine but in reality, the term intermediate-acting is arguably more accurate. (3)

How Long Does It Take Klonopin to Work?

How Long Does it Take Klonopin to Work?

Taken as prescribed, Klonopin will reach its peak concentrations in the blood within 1 to 4 hours, though you will likely feel some of the calming effects earlier than that. (2) The effects of clonazepam may last up to 12 hours.

Clonazepam is what is called “highly metabolized,” which means most of it will be processed by the body. Very little of it will leave the body unchanged, with as little as 2 percent of Klonopin being excreted in the urine unmetabolized. (2)

Klonopin takes about 1-4 hours to fully work but you may feel calming effects earlier than that.

Factors That Impact Clonazepam Absorption

The method by which a drug is taken can significantly impact the speed of absorption. 

Klonopin is generally taken orally, which is one of the slowest paths of absorption. Note that “slow” doesn’t mean ineffective. It is deliberately prescribed orally to produce the best results in patients who take it as prescribed. 

If the drug is instead snorted, as some people who misuse the medication take it, absorption will be faster. This is generally done to produce a more intense effect, resulting in a “high.” This type of drug misuse can be dangerous, increasing one’s risk for various complications, including: (1), (2)

  • Profound respiratory depression
  • Unconsciousness or coma
  • Severe confusion
  • Klonopin dependence
  • Addiction to Klonopin

Some health conditions can also affect drug absorption, such as some GI diseases, as can some drugs. This is why it’s important to talk openly with your doctor about your health and any drugs you’re taking when being prescribed any medication. The doctor needs to have an accurate understanding of how your body is likely to react to Klonopin and if any dangerous interactions might occur.

Klonopin (Clonazepam) Dosages

Klonopin dosages will depend on why the drug is being taken and can be highly variable among children, as their bodies are more varied than those of adults.

Typical doses include the following: (4)

ConditionTypical Dose
Epilepsy (Adult Dosages)1 mg taken at night, increasing to 4-8 mg over the next 2-4 weeks
Involuntary Muscle Spasms1-2 mg each day
Restless Legs Syndrome500 micrograms to 2mg each day
Children with EpilepsyDosages vary significantly for children, following similar increases over 2-4 week periods

Klonopin Prescribing Info

Dosing varies, but patients are typically started on a small dose, with their dose raised if the drug doesn’t have the desired effect. (1)

In some cases, it can take a few days to a few weeks for Klonopin to fully take effect depending on why it’s being used, such as if it is used to reduce seizures. 

When possible, it is only prescribed in the short term, as long-term use can cause a person to develop physical dependence and increase the risk of engaging in drug misuse or becoming addicted to the drug. (1)

Updated March 21, 2024
  1. Clonazepam. (May 2021). U.S. National Library of Medicine.
  2. Klonopin Tablets (clonazepam) (October 2013). U.S. Food and Drug Administration.
  3. KLONOPIN TABLETS (clonazepam). (October 2013). U.S. Food and Drug Administration.
  4. Benzodiazepines in Older Adults: A Review of Clinical Effectiveness, Cost-Effectiveness, and Guidelines [Internet] (January 2011). McIntosh B, Clark M, Spry C. Ottawa (ON): Canadian Agency for Drugs and Technologies in Health; 2011 Jan. Table 1, Pharmacokinetic Classification of Benzodiazepines Available in Canada.
  5. How and when to take clonazepam. (January 2023). United Kingdom National Health Service.
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