Pain management drugs have been on the market for many years and consist of a variety of drug classes including benzodiazepines and opiates (both synthetic and semi-synthetic). In recent years, prescriptions for various pain medications have risen dramatically. For instance, in 2011, the opiate hydrocodone was the most prescribed drug in America.1 Pain clinics, sometimes referred to as “pill mills,” have made it easier to obtain these medications because they are able to both prescribe and fulfill medications. While a good portion of patients who are prescribed these medications have a valid medical reason, it is also very clear that the ease of obtaining such prescriptions has led to increased abuse of these drugs. According to a 2010 study, an estimated 34 million people were reported to have abused pain relievers in their lifetime.2 With so many prescriptions being written for pain medications, the FDA has begun to regulate the number of refills a patient can receive and has also considered changing the classifications of some pain medications to those that are more restrictive.1
Due to the increase in both the use and abuse of pain management drugs, contract clinical and hospital labs are seeing an increase in patient samples that must be screened for a wide variety of these types of drugs. These analyses include screening for compliance and therapeutic drug monitoring as well as for identification of possible drug abuse/misuse. Many of these assays can be very challenging due to the low cut-off levels for certain pain medication panels (often at 20 to 25 ng/mL for compliance testing3) and also due to challenges from potential matrix interferences and even isomeric drug compounds (e.g., isomeric opiate species). In order to be profitable, labs that perform pain panel testing must find a means to rapidly and accurately screen for a variety of drug compounds while keeping costs at a minimum. To address these challenges, many drug testing facilities are increasingly turning to liquid chromatography with tandem mass spectrometry (LC/MS/MS) assays to obtain the necessary sensitivity and specificity for their routine, high-throughput drug screening.
Traditional pain management drug screening techniques
Pain management drug screening was traditionally performed by using an enzyme-linked immunosorbent assay (ELISA). These tests are relatively simple to use, do not require much development time, and can screen for a variety of drug compounds in a single assay.
Although ELISA screens are quick and simple, they are sometimes not available for all drug compounds of interest and cannot quantify the amount of analyte in a patient sample. Instead, a simple positive or negative result is determined based on the cut-off levels of the test. In cases where positive results are detected, confirmation may be done by gas chromatography with mass spectrometry (GC/MS) or LC/MS/MS to determine the concentration of drugs present. Although confirmation tests are performed for positive ELISAs, there is a risk that a false negative may be overlooked. In a study performed by Mikel et al.4 from Millenium Laboratories Research Center, a large percent of positive results for a variety of compounds were not detected by an ELISA and were incorrectly reported as negative (Table 1).
Table 2. Compound classification of 41 pain-management drugs
Rapid analytical method
With hundreds or even thousands of patient samples in the queue, contract clinical and hospital labs must perform rapid, yet accurate, analytical methods to detect and quantify pain management drugs. As previously mentioned, LC/MS/MS has grown to become a popular means for analyzing and quantifying pain management drugs because it provides the sensitivity needed to detect down to very low concentration levels within a sample and can also screen for a variety of pain management drugs in a single run. Developing a reliable LC/MS/MS method for analyzing a large panel of pain management drugs requires the use of an HPLC column that can resolve each compound, provide fast run times, and deliver reproducible results. On the instrument side, the mass spectrometer used must provide the sensitivity to accurately detect each compound.
Recent advances in HPLC/UHPLC column technologies include core-shell HPLC/UHPLC columns that contain a durable, homogenous porous shell which is grown on a solid silica core. This technology provides the speed and efficiencies of a smaller particle size without increasing the backpressure. This allows labs to achieve the performance advantages of UHPLC methods on a traditional HPLC without the need to invest in new capital equipment. When analyzing a panel of pain management drugs, the power of core-shell HPLC/UHPLC columns can greatly increase analysis speed, efficiencies, and resolution of target compounds. Using a 2.6-micron core-shell HPLC column, 41 pain management drugs are separated in less than five minutes (Figure 1). Coupled with a sensitive mass spectrometer, target compounds (α-hydroxyalprazolam, for example) are accurately quantified down to low concentration levels (Table 3), making LC/MS/MS a reliable means to screen for and confirm the presence or absence of pain management drugs.
Figure 1. Rapid separation of 41 pain-management drugs using a core-shell technology HPLC column
Table 3. Recovery, reproducibility and linearity of α-Hydroxyalprazolam
As the use and abuse of pain management drugs increases, contract clinical laboratories and hospital laboratories must find a way to quickly and accurately screen and confirm the presence of a variety of pain management drugs. Traditional techniques such as ELISA are not able to quantitate the amount of drugs present and can produce false negative results. With new advances in sample preparation and LC/MS/MS, laboratories can more accurately screen for a large panel of drug compounds in a single analysis and can accurately quantitate low levels of drug compounds.
Erica Pike is Clinical Industry Marketing Manager for Torrance, California-based Phenomenex.
- FDA panel wants limits on hydrocodone painkillers. USA Today. January 25, 2013.
- National Survey on Drug Use & Health. Substance Abuse and Mental Health Services Administration (SAMHSA). 2010.
- Evans M, Ma’Ayteh B, Constantine J. Therapeutic drug monitoring. Pract Pain Management. 2005;5(5).
- Mikel C, Almazan P, West R, et al. LC-MS/MS extends the range of drug analysis in pain patients. Ther Drug Monit. 2009;31(6):746-748.