The usefulness of saliva drugs of abuse testing
compared to urinary drug screening

The use of saliva as a specimen matrix for drugs of abuse screening has been cited in the literature for many years (1). There has been a comparison between saliva and urine as a specimen matrix for drugs of abuse screening that proposed the following (2) : -

One of the major disadvantage of salivary drug testing is the shorter detection times for drugs compared to urine analysis – approximately 1 day compared to 3 days as a general rule. This has obvious implications for drug screening of individuals suspected of drug abuse (3). In addition, although specific for classes of drugs and there is the potential to observe whether or not someone is under the influence of drugs at the time of screening, saliva cannot generally be screened using the standard methods that have been optimised to the likely concentrations of parent and metabolite in urine (2).

The method of saliva collection may also impact on the analytical findings determined. If the collection is stimulated to obtain sufficient specimens for testing, then it is known that the saliva flow rate is increased, leading to increased saliva pH, resulting in lower concentrations of cocaine being found. (4). This could therefore lead to false negative results being generated since cocaine was not detected more than 2 hours post intravenous drug administration.

The problem of sample volumes was discussed with respect to heroin and cocaine detection (5). It was found that to determine heroin and cocaine excretion profiles using a sensitive technique required the collection of 5 mL of saliva over a period of 30 seconds by getting subjects to expectorate 3-4 times following stimulation with citric acid. It was acknowledged that this stimulation would reduce the amount of drug present in saliva by between 25 and 54 times, again giving rise to concerns regarding drug detection times.

The detection time for cocaine following intravenous, intranasal and smoking has been found to be around 6 hours or less post administration (6). Other disadvantages of saliva as a specimen matrix for drugs of abuse screening were described as variable nature of saliva pH affecting drug excretion and detection, the influence of collection devices and procedures on drug concentration, and the possibility of saliva being contaminated by drug residues in the oral or nasal cavities.

The issue of oral contamination has been further commented upon whilst trying to determine the correlation of saliva to plasma codeine concentrations (7). It was found that despite the extensive decontamination procedures used (brushing teeth and vigorously rinsing the mouth following codeine administration) elevated saliva codeine concentrations were detected due to oral cavity contamination. This has an obvious impact on the screening for opiates in saliva since someone could take an over-the-counter codeine preparation and be detected as positive for opiates.

 To summarise, the primary advantages of saliva drug testing could be described as: - 

1)      A relatively non-invasive technique with specimen collection that can be observed without embarrassment to the person under investigation.

2)      Little chance of sample adulteration since the whole sample collection procedure can be supervised.

3)      Commercial screening devices are available for saliva monitoring that have been evaluated by some police forces for roadside drug screening use.

 The disadvantages of saliva drug testing are: - 

1)      Small specimen volumes restricting the number of analyses that can be performed

2)      Contamination of the mouth may affect drugs screening results

3)      Adulteration feasible due to oral contamination

4)      Difficult to collect from those abusing stimulants such as amphetamines and ecstasy

5)      Routine screening procedures not always applicable to screening saliva

6)      Low concentrations make detection difficult and necessitate the use of expensive equipment

It can be seen that there are both pros and cons associated with saliva as a specimen matrix for drugs of abuse screening. However, from what has been stated above, it can be seen why the majority of people employed with drugs of abuse screening tend to use urine as the specimen of choice.

References

 1)      Schramm et al. Drugs of abuse in saliva: A review. J. Anal. Toxicol. 1992; 16: 1 – 9

 2)      Cone et al. Saliva drug analysis. In Handbook of analytical therapeutic drug monitoring and toxicology. 1997; CRC Press. London.

 3)      Spieler. Pharmacology of drugs in alternative fluids. In Proceedings of Blood, Sweat and Tears conference. 1995; Cozart Bioscience. Abingdon.

 4)      Kato et al. Cocaine and metabolite excretion in saliva under stimulated and nonstimulated conditions. J. Anal. Toxicol. 1993; 17: 338-341

 5)      Jenkins et al. Comparison of heroin and cocaine concentrations in saliva with concentrations in blood and plasma. J. Anal. Toxicol. 1995; 19: 359-374

 6)      Cone et al. Cocaine disposition in saliva following intravenous, intranasal and smoked administration. J. Anal. Toxicol. 1997; 21: 465-475

 7)      O’Neal et al. Correlation of saliva codeine concentrations with plasma concentrations after oral codeine administration. J. Anal. Toxicol. 1999; 23: 452-459