Benzoylecgonine / Cocaine – Drug Testing and Elimination
Benzoylecgonine is the main metabolite of cocaine. It is used in Drug Screening Test. Many factors determine how quickly it gets cleared from the body.
It is also used medically as a topical analgesic and muscle relaxant, as in prescription drug Esterom.
When a person takes cocaine or a similar drug, it gets metabolized in the liver to form benzoylecgonine. The metabolite is then excreted out of the body via urine.
The presence of this metabolite is almost a certain indication that a person has consumed the drug.
Therefore, in cocaine users, benzoylecgonine testing in urine is commoner than testing of cocaine itself.
Time taken by a drug to get eliminated from the body
- The amount of drug taken
- How frequently or regularly you are taking it
- Individual body weight and height
- Your overall rate of metabolism, which depends on your levels of activity and health status.
Elimination from Urine
Threshold Value for Detection
Levels of 2 ng/mL or more produce a positive drug test result.
Around 30 to 40% of cocaine is metabolized by enzymes in the liver to form ecgonine methly ester. Another 30 to 40% is hydrolyzed spontaneously without enzymes to form benzoylecgonine.
Both of them are water soluble compounds and are active. While cocaine has a half life of only 1.5 hours, benzoylecgonine has a half life of 7.5 hours.
Types of Drug Screening
Saliva test- Cocaine is detectable in saliva after 5 to 10 minutes of taking the drug. It may be detected in saliva till 2 to 4 days.
Urine test- Detectable after 2 to 5 hours of use, till a period of 3 to 4 days.
Blood testing is more specific. The presence of the drug is detected after 5 to 6 hours till around 5 to 7 days or even more.
Hair test- The drug starts showing in hair after 5 to 7 days till around 80 to 90 days.
Urine testing is most popular because it is painless, easy and inexpensive. Home kits available in the market are also based on urine testing.
Detection in Chronic Users
In long-term or regular users, the drug is stored in the fatty tissues, especially of the liver. After each use, a fraction of the drug consumed is stored, adding up to the stock each time.
This stored drug is released on a continuous basis into the blood stream. So the user is detected positive even if he doesn’t take the drug for some time.
Total cleansing of the user takes 5 to 6 months, after which he can be called drug-free.
False Positive Test Results
People often complain of positive results with urine drug testing for cocaine, when they have not taken this drug at all.
This may happen. False positives do occur.
Firstly, it is not cocaine itself that is screened in urine. Actually it gets out of urine in as little as 12 hours, so its testing would be a waste.
The metabolite of cocaine, benzoylecgonine, is screened by most of the testing labs. This shows in urine till 3 to 5 days, or even a month if the dose taken was heavy.
It’s a fingerprint metabolite of cocaine. No other drug or prescription medicine produces exactly the same metabolite as benzoylecgonine.
However, certain medicines produce metabolites that are similar in structure to benzoylecgonine. So labs with cruder instruments may label you as ‘positive’, if you are consuming these medications.
Some of the medications that may produce false positive test results include local anesthetics that are used by dentists, including lidocaine, Novocain and tonic water.
Apart from these, patients with chronic liver or kidney diseases may also show altered results.
What to do if you get a false positive result?
Immediately request for a confirmation test.
The standard EMIT test used by most labs can be confirmed by GC/MS (gas chromatography/ mass spectrometry) test. This detects the benzoylecgonine structure with more specificity, screening out similar looking compounds.