Toxicology screen (patient information)
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Editor-in-Chief: C. Michael Gibson, M.S.,M.D. [1] Phone:617-632-7753; Associate Editor-In-Chief: Lakshmi Gopalakrishnan, M.B.B.S.
Overview
A toxicology screen refers to various tests to determine the type and approximate amount of legal and illegal drugs a person has taken.
How is a toxicology screen performed?
Toxicology screening is most often done using a blood or urine sample. However, it may be done soon after swallowing the medication, using stomach contents that are obtained through gastric lavage or after vomiting.
How to prepare for a toxicology screen?
- No special preparation is needed.
- If able, tell your health care provider what drugs (including over-the-counter medications) you have taken, including when and how much.
- This test is sometimes part of an investigation for drug use or abuse. Special consents, handling and labeling of specimens, or other special procedures may be required.
How will a toxicology screen feel?
- Blood test: When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
- Urine test: A urine test involves normal urination. There is no discomfort.
Why is a toxicology screen performed?
- This test is often done in emergency medical situations.
- It can be used to evaluate possible accidental or intentional overdose or poisoning.
- It may help determine the cause of acute drug toxicity, to monitor drug dependency, and to determine the presence of substances in the body for medical or legal purposes.
- Additional reasons the test may be performed:
- Alcoholism
- Alcohol withdrawal state
- Altered mental state
- Analgesic nephropathy (kidney poisoning)
- Complicated alcohol abstinence ([[Delirium tremens (patient information)|delirium tremens)
- Delirium
- Dementia
- Drug abuse monitoring
- Fetal alcohol syndrome
- Intentional overdose
- Seizures
- Stroke secondary to cocaine
- Suspected sexual assault
- Unconsciousness
- If the test is used as a drug screen, it must be done during a certain time period after the drug has been taken or while forms of the drug can still be detected in the body. Examples are below:
- Alcohol: 3 to 10 hours
- Amphetamines: 24 to 48 hours
- Barbiturates: up to 6 weeks
- Benzodiazepines: up to 6 weeks with high level use
- Cocaine: 2 to 4 days; up to 10 to 22 days with heavy use
- Codeine: 1 to 2 days
- Heroin: 1 to 2 days
- Hydromorphone: 1 to 2 days
- Methadone: 2 to 3 days
- Morphine: 1 to 2 days
- Phencyclidine (PCP): 1 to 8 days
- Propoxyphene: 6 to 48 hours
- Tetrahydrocannabinol (THC): 6 to 11 weeks with heavy use
What are normal results?
- Normal value ranges for over-the-counter or prescription medications may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
- A negative value usually means that alcohol, prescription medications that have not been prescribed, and illegal drugs have not been detected.
- A blood toxicology screen can determine the presence and level (amount) of a drug in your body.
- Urine sample results are usually reported as positive (substance is found) or negative (no substance is found).
What do abnormal results mean?
- Elevated levels of alcohol or prescription drugs can be a sign of intentional or accidental intoxication or overdose.
- The presence of illegal drugs or drugs not prescribed for the person indicates illicit drug use.
What are the risks?
- Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
- Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Considerations
Substances that may be detected on a toxicology screen include:
- Alcohol (ethanol) -- "drinking" alcohol
- Amphetamines
- Antidepressants
- Barbiturates and hypnotics
- Benzodiazepines
- Cocaine
- Flunitrazepam (Rohypnol)
- Gamma hydroxybutyrate (GHB)
- Marijuana
- Narcotics
- Non-narcotic pain medicines including acetaminophen and anti-inflammatory drugs
- PCP
- Phenothiazines (antipsychotic or tranquilizing medications)
- Prescription medications, any type