American Society of Regional Anesthesia and Pain Medicine May 2017 - 18
Genotyping and Phenotyping in Pain Management
A
ccording to the American Academy of Pain Medicine, chronic
pain is an epidemic affecting approximately 1.5 billion people
worldwide. With age comes more pain related problems.
Cross sectional studies of patients with neuropathic pain have
shown that even with pharmacological treatment, moderate or
severe pain continues. Part of the difficulty is the heterogeneity
of causes and symptoms that vary from individual to individual.
Physicians who treat patients with pain note a marked variability
in pain responses among patients. Physicians often treat these
patients with the same arsenal of medications on a trial and error
basis. This method may be time consuming and even potentially
harmful to patients. Response to pain and medications may be
partially but significantly influenced by genetic and phenotypic
makeup. In the 1890s, Wilhelm Johannsen was the first to
introduce the terms genotype and phenotype.1 Genotype refers
to the genetic components of an individual. Phenotype refers to
the set of observable characteristics of an individual from the
interaction of its genotype with the environment.
Under or overdosing is possible when patients respond differently
to medications. Without knowledge of a patient's genetic makeup,
treatment plans cannot be tailored to individual patient's needs.
Pain is influenced by many factors, including genetic predisposition,
prior experiences, physiological status, mood, coping skills,
and sociocultural background.2 The extent to which each of
these factors has on the pain
experience is unclear.
Lynn Kohan, MD
Pain Medicine Fellowship
Department of Anesthesiology
University of Virginia Health System
Charlottesville, Virginia
Dalia Elmofty, MD
Department of Anesthesia and
Critical Care
University of Chicago
Chicago, Illinois
Section Editor: Magdalena Anitescu, MD
score of 4-6; and (3) severe pain, a score of 7-10. The DRD1 gene
variant was 33% more prevalent in the low pain group than in the
severe pain group. COMT and OPRK variants were 25% and 19%
more prevalent, respectively, in the moderate pain group compared
to the severe pain group. The DRD2 variant was 25% more common
among those with severe pain than those with moderate pain.3
"Pain is influenced by many factors,
including genetic predisposition, prior
experiences, physiological status,
mood, coping skills, and sociocultural
background."
Several genes likely affect the
pain experience and analgesic
response. Two hereditary
disorders are known to make
individuals insensitive to pain:
hereditary insensitivity to pain
with anhydrosis and familial
dysautonomia. As our knowledge
grows, so may our ability to understand why pain persists in some
patients but not others-despite identical traumas-or why some
people have a low tolerance to pain while others have a much
higher tolerance.
A recent study presented by Dr. Onojjighofia at the American
Academy of Neurology's 66th Annual Meeting suggests that four
genes may be involved in pain tolerance. His study examined
2,721 people diagnosed with chronic pain. The genes involved
were catechol O methyltransferase (COMT), dopamine receptor D2
(DRD2), dopamine receptor D1 (DRD1), and opioid receptor kappa
1 (OPRK1). These four genes help to determine the pain threshold
in individuals. Participants were taking opioid pain medications
and rated pain from a 0 to 10. Patients with 0 pain were excluded
from the study. Patients were divided into three groups according to
pain perception: (1) low pain, a score of 1-3; (2) moderate pain, a
18
2
While these sequence
variations in DNA (SNPs) may
help predict the likelihood of
individual pain sensitivity, DNA
testing should not be used to
diagnose pain according to the
Medical Treatment Utilization
Schedule (MTUS) guidelines.4
Although we may not use
genetic testing to diagnose
pain, genetic testing may affect the selection of medications used
to treat it.
There are several reasons to consider genetic testing. Medications
may be metabolized slowly in individuals with a genetic
polymorphism that eliminates or decreases enzyme activity. Such
patients may be at risk of an adverse drug reaction (ADR) or
therapeutic failure. In addition, drug therapy may be ineffective if a
drug is metabolized too quickly because of genetic polymorphism.
Knowledge of these polymorphisms before initiating drug therapy
could help in choosing the most efficacious agent and in decreasing
the risk of ADRs.
Patients can be classified by how effectively they metabolize
a medication according to how many copies of normal versus
abnormal alleles they have inherited (Table 1).
American Society of Regional Anesthesia and Pain Medicine
2017
Table of Contents for the Digital Edition of American Society of Regional Anesthesia and Pain Medicine May 2017
No label
American Society of Regional Anesthesia and Pain Medicine May 2017 - No label
American Society of Regional Anesthesia and Pain Medicine May 2017 - 2
American Society of Regional Anesthesia and Pain Medicine May 2017 - 3
American Society of Regional Anesthesia and Pain Medicine May 2017 - 4
American Society of Regional Anesthesia and Pain Medicine May 2017 - 5
American Society of Regional Anesthesia and Pain Medicine May 2017 - 6
American Society of Regional Anesthesia and Pain Medicine May 2017 - 7
American Society of Regional Anesthesia and Pain Medicine May 2017 - 8
American Society of Regional Anesthesia and Pain Medicine May 2017 - 9
American Society of Regional Anesthesia and Pain Medicine May 2017 - 10
American Society of Regional Anesthesia and Pain Medicine May 2017 - 11
American Society of Regional Anesthesia and Pain Medicine May 2017 - 12
American Society of Regional Anesthesia and Pain Medicine May 2017 - 13
American Society of Regional Anesthesia and Pain Medicine May 2017 - 14
American Society of Regional Anesthesia and Pain Medicine May 2017 - 15
American Society of Regional Anesthesia and Pain Medicine May 2017 - 16
American Society of Regional Anesthesia and Pain Medicine May 2017 - 17
American Society of Regional Anesthesia and Pain Medicine May 2017 - 18
American Society of Regional Anesthesia and Pain Medicine May 2017 - 19
American Society of Regional Anesthesia and Pain Medicine May 2017 - 20
American Society of Regional Anesthesia and Pain Medicine May 2017 - 21
American Society of Regional Anesthesia and Pain Medicine May 2017 - 22
American Society of Regional Anesthesia and Pain Medicine May 2017 - 23
American Society of Regional Anesthesia and Pain Medicine May 2017 - 24
American Society of Regional Anesthesia and Pain Medicine May 2017 - 25
American Society of Regional Anesthesia and Pain Medicine May 2017 - 26
American Society of Regional Anesthesia and Pain Medicine May 2017 - 27
American Society of Regional Anesthesia and Pain Medicine May 2017 - 28
American Society of Regional Anesthesia and Pain Medicine May 2017 - 29
American Society of Regional Anesthesia and Pain Medicine May 2017 - 30
American Society of Regional Anesthesia and Pain Medicine May 2017 - 31
American Society of Regional Anesthesia and Pain Medicine May 2017 - 32
American Society of Regional Anesthesia and Pain Medicine May 2017 - 33
American Society of Regional Anesthesia and Pain Medicine May 2017 - 34
American Society of Regional Anesthesia and Pain Medicine May 2017 - 35
American Society of Regional Anesthesia and Pain Medicine May 2017 - 36
American Society of Regional Anesthesia and Pain Medicine May 2017 - 37
American Society of Regional Anesthesia and Pain Medicine May 2017 - 38
American Society of Regional Anesthesia and Pain Medicine May 2017 - 39
http://www.brightcopy.net/allen/asra/18-04
http://www.brightcopy.net/allen/asra/18-3
http://www.brightcopy.net/allen/asra/18-2
http://www.brightcopy.net/allen/asra/18-1
http://www.brightcopy.net/allen/asra/17-4
http://www.brightcopy.net/allen/asra/17-3
http://www.brightcopy.net/allen/asra/17-2
http://www.brightcopy.net/allen/asra/17-1
http://www.brightcopy.net/allen/asra/16-4
http://www.brightcopy.net/allen/asra/16-3
http://www.brightcopy.net/allen/asra/16-2
http://www.brightcopy.net/allen/asra/16-1
http://www.brightcopy.net/allen/asra/15-4
http://www.brightcopy.net/allen/asra/15-3
https://www.nxtbook.com/allen/asra/15-2
https://www.nxtbook.com/allen/asra/15-1
https://www.nxtbookmedia.com