How Long Does Demerol Stay in Your System?

Demerol (meperidine) can typically stay in your system for approximately one to three days, but individual factors such as metabolism, dosage and frequency of use can influence the exact timeline.

The drug’s half-life, or the time it takes for half the drug to leave the body, ranges from one to five hours. Demerol can be detected in hair for up to 90 days, urine for two to four days, saliva for one to three days and blood for about 24 hours.

Factors like metabolism, dosage, frequency of use and physical health can affect detection times.

Duration of Demerol’s Effects

How long the effects of Demerol last can vary greatly based on all the same factors that impact how long Demerol will remain in the system. These include factors like the route of administration, individual metabolism and health, and other drugs that are used.

In general, the estimated duration of effect of Demerol is largely impacted by route of administration.

• Oral ingestion: When Demerol is taken orally in the form of tablets or capsules, its effects typically begin within 30 minutes to an hour and can last for approximately four to six hours.
• Intramuscular injection: When Demerol is administered via intramuscular injection, the onset of effects is usually faster than oral ingestion, occurring within 15 to 30 minutes.[1] The duration of action can last for around two to four hours.
• Intravenous injection: With intravenous administration, Demerol’s effects are felt almost immediately, often within a few minutes.[2] The duration of action is relatively short, however, lasting for about one to two hours.

These timeframes are approximate and can vary widely even in the same person. One cannot always expect to feel the effects of Demerol in the exact same time frame even if the drug is ingested the same way each time. Metabolism, slight changes in the purity of the product, other substances that it is cut with, overall health and more can significantly impact the individual experience of Demerol use.

Additionally, the duration of pain relief may not necessarily match the duration of other effects, such as sedation or respiratory depression.

Demerol’s Half-Life

The half-life of Demerol refers to the time it takes for half of the drug to be eliminated from the body.[3] 

Again, the exact timeline will vary based on individual details, but the estimated half-lives for different ingestion types include the following:

• Oral ingestion: Its average half-life is approximately two to five hours. This means that it takes about this long for half of the ingested dose to be eliminated from the body.
• Intramuscular injection: The half-life of Demerol after intramuscular injection is similar to oral ingestion, ranging from two to five hours.
• Intravenous injection: The half-life of Demerol after intravenous injection is shorter, averaging around two to three hours.

It is important to note that the effects of Demerol use last far less time than the drug remains in the system. For example, though the effects of oral ingestion of Demerol last only about five hours, half of that dose is still in the body at the five-hour mark. 

That means that taking another dose right away can mean that there is an even higher level of Demerol in the system than prescribed. This can increase the risk of overdose and lengthen the amount of time that Demerol remains in the body.

How Long Does Demerol Remain in Your System?

The detection window for Demerol can vary depending on the drug testing method used.[4] Drug testing variations include the following:[4]

• Hair tests: Demerol can be detected in hair follicle tests for a longer time period compared to other methods. In general, Demerol can be detected for up to 90 days or longer after use, as hair growth provides a long historical record of chemical exposure.
• Urine tests: Demerol can generally be detected in urine for about one to two days after last use. However, this detection window can vary depending on various factors, such as the person’s metabolic process, the dose taken, the frequency of doses, other medications and underlying health. In most cases, these issues will lengthen the amount of time that Demerol is detectable in urine. 
• Saliva tests: Demerol can typically be identified in saliva for a shorter duration compared to urine. It is usually detectable within 24 to 48 hours after use, but the exact detection window can vary.
• Blood tests: Demerol has a relatively short detection window in blood tests, and it usually only shows up in the first 24 hours after use.

Factors That Impact Length of Detectability

Several factors can influence the length of detectability of Demerol in drug screenings. In some cases, these factors shorten that window, but in others, they make the window longer.

These factors include the following:

• Dosage: Higher doses of Demerol may take longer to be eliminated from the body, potentially extending the detection window.
• Frequency of use: Regular or chronic use of Demerol can lead to its accumulation in the body, resulting in a longer detection period compared to occasional or one-time use.
• Individual metabolism: Metabolic rate varies among individuals and can affect how quickly Demerol is processed and eliminated from the body. Faster metabolism may result in a shorter detection window, while slower metabolism does the opposite. 
• Body mass: Body composition, including factors like body fat percentage and hydration levels, can influence the distribution and elimination of Demerol, potentially impacting the detectability window.[5]
• Route of administration: The method of Demerol administration (oral ingestion, intramuscular injection, or intravenous injection) can affect how quickly the drug is absorbed, metabolized and eliminated, potentially impacting detection times.
• Testing method sensitivity: Different drug testing methods have varying levels of sensitivity and detection thresholds. Some methods may be able to detect lower concentrations of Demerol, which makes it easier to identify in the bloodstream for a longer period after last use.

How Does the Body Metabolize & Break Down Demerol?

Demerol is primarily broken down and processed in the liver. The process involves several enzymatic reactions, but the main pathway of Demerol metabolism is through several enzymes including cytochrome P450. These enzymes break down Demerol into a substance Normeperidine. 

Normeperidine is an active metabolite that has similar opioid properties to Demerol but with a much longer half-life.[6] It is important to note that normeperidine can accumulate in the body with repeated or prolonged use of Demerol. High levels of normeperidine may lead to adverse health effects and medical complications, such as seizures and central nervous system excitation.[7]

After metabolism, Demerol and its metabolites are eliminated from the body primarily through the kidneys via urine, while some small amounts may also be excreted in feces. The elimination half-life of Demerol is approximately two to five hours, meaning it takes about this long for half of the drug to be cleared from the body, while the other half of the dose will remain. 

Individual factors such as liver function, genetic variations in enzymes and overall health can influence the rate of Demerol metabolism and elimination. For this reason, it is not always easy to guess whether or not Demerol will show up on a drug test even if attention is paid to specific timelines and elimination estimates.