How long can a drug stay in the system?

Approximate detection times.

Drug
Urine
Saliva
 
Amphetamine
1-4 Days
Up to 2 Days
 
Barbiturates
1 Day (Short acting drugs)
2-3 Weeks (long acting drugs)
Up to 2 Days
 
Benzodiazepines
3-7 Days
3 Weeks (prlonged use)
Up to 2 Days
 
Cocaine
2-4 Days
7 Days (chronic use)
Up to 2 Days
 
Methadone
3 Days
Up to 2 Days (Occasional Use)
Up to 3-5 Days (Chronic Use)
 
Methamphetamine
See Amphetamine
See Amphetamine
 
Phencyclidine (PCP)
5-8 Days
Up to 30 Days (chronic use)
Up to 2 Days
 
THC
5 Days (moderate use)
10 Days (heavy use)
30+ Days (chronic use)
Up to 2 Days
 

Note: The above chart gives approximate detection periods. The ranges depend on frequency of use, body metabolism and rate, body mass, age, drug tolerance etc..

When and Why to Choose:

Oral Fluid (Saliva)
Urine
Hair
Recent use which indicates the user was under influence at time of collection.

Correlates more closely with blood than urine or hair.
Longer detection of drugs and their metabolites.

Economic alternative to saliva and hair.
90 Day Detection

Drugs used in chronic manner.

Assists in history of drug use.