Toxicology screen (patient information)

Editor-in-Chief: C. Michael Gibson, M.S.,M.D. [mailto:mgibson@perfuse.org] 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

Source
http://www.nlm.nih.gov/medlineplus/ency/article/003578.htm