Mark asked
Hello, my question is my daughter, age 28 has been on subutex for 1.5 years (16 mg daily). She is 14 days clean and the subutex is still showing up in her urine. Is this possible or probable? She has not been eating or drinking much since, could that be the problem?
Answer
There is no simple answer to your inquiry as many different factors can affect how long a drug is detectable in someones system. Having said that, we can certainly provide you some information that can help you better understand the typical detection times for Subutex (Buprenorphine). Specifically answering your question with all the available information at hand, it is VERY probable that the drug is showing up in the urine, even 15 days after stopping the medication.
Subutex (Buprenorphine) is an opioid drug that is structurally similar to morphine. It is most often used for either pain control or opioid dependence/withdrawal. The drug does have some unusual characteristics that vary from many of the other drugs in the opioid class. While most drugs in the class tend to be metabolized and excreted from the body fairly quickly, buprenorphine hangs around for a long time!
When talking drug tests, a common measure in determining how long a drug lasts in the body is half life. A half life is the amount of time that it takes for 50% of a drug to be metabolized. For example, if a drug has a half life of 10 hours, 10 hours after that drug is absorbed, only 50% will be remaining in the body. Half lives are used to approximate how long a drug will be detectable via a test. The rule of thumb is that it takes about 5 half lives for a drug to become undetectable. Let's use the example of the drug with a 10 hour half-life:
Half Life | Time Elapsed (hours) | % Drug Remaining |
0 | 0 | 100 |
1 | 10 | 50 |
2 | 20 | 25 |
3 | 30 | 12.5 |
4 | 40 | 6.25 |
5 | 50 | 3.125 |
Based on the chart above, we see that after 50 hours, only 3.125% of the original drug is left in our body based on the half-life. It all depends on the sensitivity of the drug test being administered, but 5 half-lives is generally a good mark to predict when a drug will no longer be detectable.
As mentioned previously, buprenorphine acts differently from other opioid drugs in terms of how long it lasts. The average half-life for the drug as recorded in the drug information from the manufacturer is 37 hours! There is also of course variability between how people metabolize drugs. Typically, patients that are on a drug for a long time have detectable levels of the drug in their body for a longer period than someone who took only one or two doses.
In addition to half-life, there are two additional major factors that affect how long a drug is detectable. Firstly, most drugs are either lipophilic (stay in fat) or hydrophilic (do not stay in fat, only in water). Drugs that are lipophilic are actually stored in fat and therefore are released at a slow rate over a long period of time, well after you would think they would be gone based on half-life. Marijuana is a great example of a lipophilic drug. Chronic users have detectable levels in their body sometimes months after they have exposed themselves to it! Subutex is known to be very lipophilic.
The second additional factor is whether or not a drug has detectable metabolites. Metabolites are by-products of metabolism from the original drug. When Subutex is metabolized, it breaks down into a compound known as norbuprenorphine. This by-product has a longer half life than buprenorphine! The half-life has been reported to be around 50-100 hours! Some drug tests look for metabolites and some don't.
If you look at the answer on our website, we have included a picture of a study that was done to determine the pharmacokinetic properties of buprenorhpine and norbuprenorphine. Pharmacokinetics is simply the study of how drugs are absorbed, distributed, metabolized and excreted in the body. Highlighted in red is the information for half-life. We can see there is tremendous variability in half life among the patients in the study! We also see how much longer norbuprenorphine lasts!
In summary, there are 3 major factors to consider when determining how long a drug lasts in the body. Let's apply them all to Subutex (Buprenorphine).
- Is Subutex (Buprenorphine) lipophilic? Yes
- Does Subutex (Buprenorphine) have detectable metabolites? Yes.
- Half life? Subutex (Buprenorphine) ~ 37 hours.
- Half life of norbuprenorphine? ~100 hours.
So based on half-lives, how long could we expect your daughter to have detectable drug levels?
Subutex(Buprenorphine) - Half Life 37 Hours
Half Life | Time Elapsed (hours) | % Drug Remaining |
0 | 0 | 100 |
1 | 37 | 50 |
2 | 74 | 25 |
3 | 111 | 12.5 |
4 | 148 | 6.25 |
5 | 187 | 3.125 |
For the average person, it will take 187 hours (7.8 days) for 5 half lives to occur. Remember that since your daughter has been on the medication for a long time, and adding in the fact that the drug is lipophilic, it may be detectable for a longer period of time. If the drug test is also looking for metabolites:
Norbuprenorphine - Half Life 100 Hours
Half Life | Time Elapsed (hours) | % Drug Remaining |
0 | 0 | 100 |
1 | 100 | 50 |
2 | 200 | 25 |
3 | 300 | 12.5 |
4 | 400 | 6.25 |
5 | 500 | 3.125 |
5 half-lives occur after 500 hours (20.8 days).
As mentioned earlier, it is very probable that the drug is still being detected in the urine after 15 days based on the duration of drug use, the long half life of both the parent drug (Subutex) and metabolite (Norbuprenorphine), and the lipophilicity of the drug. Fortunately, the lipophilicity of the drug usually is not an important factor in urine tests, so that really leaves the variability in half lives. Amount of food or liquid consumed should really have no bearing on drug levels in this case.
My best guess is that your daughter would be drug free after about 25-30 days if the test is looking for metabolites. If there are conditions in her life that requires her to have negative drug tests, the administrators of the drug tests should be well aware of the variability with Subutex. The concentrations of drug measured each test should be decreasing each and every time and hopefully your daughters body will be clear of it soon enough.
