Toxicology screen (patient information)

A toxicology screen refers to various tests to determine the type and approximate amount of legal and illegal drugs a person has taken.

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.

• 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.

• 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.

• 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

• 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).

• 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.

• 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)

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

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

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