Pain Management (via Pharmacotherapy)

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Pain Management (via Pharmacotherapy)

• Stephanie Riccalarsen, M.D.

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• Pain is an unpleasant sensory and emotional
  experience associated with actual or potential
  tissue damage.

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Pain

• Pain is subjective there is no test that can
  measure pain.
• Mostly, we have to accept the patients report of
  pain, which is not always easy.
• Perception of pain is influenced by cultural,
  psychological, and emotional factors.

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Trying to Objectify Pain

• Tachypnea
• Grimace
• Grinding/Bruxism
• Tachycardia
• Guarding
• Rigidity
• Sweating
• Rocking
• Clutching
• Irritability

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Pain

• Acute vs. Chronic
• Acute pain is usually related to an easily
  identified event or condition.
• Chronic pain may or may not be related to an
  easily identified pathophysiologic phenomenon,
  may be multifactorial, and may be present for an
  indeterminate period of time.

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Pain Classifications

• Nociceptive pain involves direct stimulation of
  intact mechanical, chemical, or thermal
  nociceptors, and transmission of electrical
  signals along normally functioning nerves.
  (Divided into somatic and visceral.)
• Neuropathic pain disordered function of
  peripheral or central nervous system. Responds
  best to anti-depressants and anti-convulsants,
  and occasionally with topical local anesthetics.
  Otherwise beyond the scope of this presentation.

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Nociceptive Pain Subtypes

• 1. Somatic skin, soft tissue, muscle, bone.
  Due to stimulation of somatic nervous system.
• 2. Visceral cardiac, lung, GI and GU tracts.
  Results from stimulation of the autonomic nervous
  system. Patients may find this pain difficult to
  describe or localize.

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The WHO 3-Step Model

• Step 1 Mild pain (1-3/10 on pain scale)
• Aspirin
• Acetaminophen
• Nonsteroidal Anti-Inflammatory Drugs

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The WHO 3-Step Model

• Step 2 Moderate pain (4-6/10)
• Acetaminophen or aspirin, plus
• Codeine
• Hydrocodone
• Oxycodone
• Oxymorphone or
• Tramadol (not available with aspirin, Ultracet is
  tramadol with acetaminophen)

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The WHO 3-Step Model

• Step 3 Severe pain (7-10/10)
• Morphine
• Hydromorphone (Dilaudid)
• Methadone
• Levorphanol
• Fentanyl
• Oxycodone
• /- Nonopioid analgesics

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It is not necessary to traverse each step
sequentially a patient with severe pain may need
to have step 3 opioids right away.
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Acetaminophen

• Acetaminophen is an effective step 1 analgesic.
• It is also useful as a coanalgesic in many
  situations.
• Its site and mechanism of action are not known.
  It is presumed to have a central mechanism.
• It does not have signficant anti-inflammatory
  effects.

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Acetaminophen Adverse effects

• Doses greater than 4g per 24 hours are not
  recommended as they may cause hepatotoxicity.
• Hepatic disease or heavy alcohol use increases
  this risk further.
• On the outpatient basis, patients may not realize
  their Lortab, Percocet, etc., has acetaminophen
  included (it is called apap on the prescription
  bottle) and they may then take additional
  separate acetaminophen, increasing risk of
  accidental overdose and hepatotoxicity.

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NSAIDs

• NSAIDs are effective step 1 analgesics
• They may also be useful coanalgesics
• They are effective for bone and inflammatory
  pain.
• They work in part by inhibiting cyclo-oxygenase
  (COX), the enzyme that converts arachidonic acid
  to prostaglandins.
• All NSAIDs inhibit COX but vary in COX-2
  selectivity.
• Ketorolac (Toradol) is available in an
  intravenous formulation

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NSAIDs Adverse effects

• Potential adverse effects, irrespective of route
  of administration, include gastropathy, renal
  failure, and inhibition of platelet aggregation.
• The nonselective medications are relatively
  contraindicated in the setting of preexisting
  renal insufficiency.
• If bleeding is a problem, or coagulation or
  platelet function is impaired, NSAIDs may be
  contraindicated.

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Opioid Adverse Effects

• Respiratory depression not seen when titrated
  to pain control. Pain control is generally
  achieved before respiratory depression.
• Sedation.
• Constipation.
• Conjugated by the liver and excreted by kidneys,
  thus disease in either location affects dosing
  frequency and amount.

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Opioid Pharmacology

• Opioids reach their peak plasma concentration
  approximately
• 60 to 90 minutes after oral or rectal
  administration
• 30 minutes after subQ or IM injection
• 6 minutes after intravenous administration
• When renal clearance is normal, hydrocodone,
  hydromorphone, morphine, oxycodone, and their
  metabolites all have effective half-lives of
  about 3-4 hours.
• When dosed repeatedly, their plasma
  concentrations approach a steady-state after 4 to
  5 half lives.

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Selecting An Opioid

• Extended release formulations are available but
  are not often used on an inpatient basis for
  acute pain.
• Methadone has a long and variable half-life and
  is best used on an outpatient basis for chronic
  pain, thus it has little use on the inpatient
  service.

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NOT RECOMMENDED

• Meperidine (Demerol) Its principal metabolite,
  normeperidine, has no analgesic properties of its
  own, has a longer half-life of about 6 hours, is
  renally excreted, and produces significant
  adverse effects when it accumulates
  (tremulousness, dysphoria, myoclonus, and
  seizures)

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NOT RECOMMENDED

• Propoxyphene (Darvon) and Propoxyphene with
  acetaminophen (Darvocet) Most pain experts
  believe that these have more dependence and
  mental status risk, with rather poor pain relief
• No better than placebo in most studies
• Low efficacy at commercially available doses.
• Dose escalation could lead to accumulation of a
  toxic metabolite

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Inpatient Recommended Opioids (Intravenous)

• Get comfortable with one or two good IV opioid
  medications, like morphine and dilaudid, and
  stick with them.
• Remember that dilaudid is 51 more potent than
  morphine 2 mg of morphine is about equivalent to
  0.5 mg of dilaudid.
• Common side effects include constipation, nausea,
  vomiting, itching, and skin flushing. Individual
  patients may tolerate one but not the other.

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Commonly Used Oral Inpatient Opioids

• Oxycodone is available in oral formulation by
  itself.
• Percocet is oxycodone with acetaminophen,
  available with 5/325mg dosing as well as 10/325mg
  dosing, so 2 tabs may be used every 4 hours
  instead of every 6 without going over the
  acetaminophen limit.
• Oxycodone is more regulated, so an outpatient
  prescription cannot be called in a physical
  prescription must be written and received by the
  patient.

• Hydrocodone is not available in oral formulation
  by itself.
• Lortab/Vicodin is hydrocodone 5/500mg so each
  tablet comes with more acetaminophen, meaning if
  you use a 2 tablet dose, it cannot be given more
  frequently than q 6 hours.
• Hydrocodone is less regulated than oxycodone, and
  a prescription containing it may be called in to
  a pharmacy over the phone.

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Sources

• 1. Mark Goodman, M.D., Pain Management in
  Obstetrics and Gynecology Grand Rounds, 2006.
  Department of Family Medicine, Creighton
  University.
• 2. Frederick E. Youngblood, M.D., CME
  Presentation October 14, 2005. Department of
  Anesthesiology, Creighton University.
• 3. Robert H. Lurie Comprehensive Cancer Center of
  Northwestern University http//endoflife.northwes
  tern.edu Module 4 Pain Management.
• 4. Journal of Pain and Symptom Management Issue
  29 Vol 1, Jan 2005 pg 2-13.
• 5. Whitecar, Jonas, Clasen. Managing Pain in
  the Dying Patient. American Family Physician.
  Feb 1,2000/Vol 61, No 3.