Pharmacology Chapter 8

What are the four steps of the pain pathway?

Transduction, transmission, modulation, perception.

What is a nociceptor?

A pain receptor.

What type of pain do A-delta fibers transmit?

Sharp, localized pain.

Are A-delta fibers myelinated or unmyelinated?

Myelinated.

What type of pain do C fibers transmit?

Dull, aching pain.

Are C fibers myelinated or unmyelinated?

Unmyelinated.

What is hyperalgesia?

Increased sensitivity of adjacent pain receptors to painful stimuli.

What is hyperesthesia?

Increased sensitivity to any stimulus.

What is wind-up?

A phenomenon where the spinal cord initially dampens pain impulses but over time transmits more pain signals to the brain.

Why is it important to provide analgesia before a patient wakes up from anesthesia?

To prevent wind-up and reduce postoperative pain.

What is somatic pain?

Pain involving the skin, muscles, joints, and bones.

What is visceral pain?

Pain involving internal organs.

What are the major classes of analgesics?

Corticosteroids, NSAIDs, opioids, gabapentin, NMDA receptor antagonists, monoclonal antibodies, and alpha-2 agonists.

What is the primary pain receptor targeted by opioids?

Mu (μ) receptor.

Where are mu receptors primarily located?

In the central nervous system.

What effects result from mu receptor stimulation?

Analgesia, narcosis, respiratory depression, and euphoria.

Which opioid receptor provides milder analgesia and less respiratory depression?

Kappa (κ) receptor.

Which opioid receptor provides spinal cord analgesia?

Delta (δ) receptor.

What is neuroleptanalgesia?

A combination of an opioid with a sedative or tranquilizer.

Why are opioids considered controlled drugs?

They have potential for addiction and abuse.

What happens to opioid dosing over time with chronic use?

Tolerance develops, requiring higher doses.

What is the most serious adverse effect of opioids?

Respiratory depression.

How do opioids affect the gastrointestinal tract?

They decrease GI motility and may cause constipation.

How do opioids affect the cough reflex?

They suppress it.

Which opioid is considered the prototype full mu agonist?

Morphine.

What types of pain does morphine treat?

Mild visceral and somatic pain.

What adverse effects can morphine cause?

Vomiting, histamine release, and dysphoria.

Which opioids are more potent than morphine?

Hydromorphone and oxymorphone.

Which opioid has been associated with hyperthermia in cats?

Hydromorphone.

Which opioid is more potent than morphine but has a shorter duration?

Fentanyl.

How can fentanyl be administered?

CRI and transdermal patch.

Which opioid is also an NMDA receptor antagonist?

Methadone.

Which opioid is least likely to cause vomiting?

Methadone.

Which partial mu agonist has a ceiling effect?

Buprenorphine.

What is the ceiling effect?

Increasing the dose does not increase analgesia.

How is buprenorphine commonly administered to cats?

Through the oral mucous membranes (transmucosally).

What is the long-acting transdermal buprenorphine product for cats?

Zorbium.

How long does Zorbium last?

Approximately 4 days.

Which opioid is a kappa agonist and mu agonist/antagonist?

Butorphanol.

What type of pain does butorphanol treat best?

Mild visceral pain.

Which opioid is also used as a cough suppressant?

Butorphanol.

How is tramadol metabolized differently in dogs and cats?

Cats metabolize it better than dogs.

What neurotransmitters are affected by tramadol?

Norepinephrine and serotonin.

What serious drug interaction is associated with tramadol?

Serotonin syndrome when combined with SSRIs or tricyclic antidepressants.

Which drug completely reverses opioid effects?

Naloxone (Narcan).

Will naloxone reverse apomorphine?

No.

What is gabapentin primarily used for?

Neuropathic pain.

What additional use does gabapentin have?

Anticonvulsant therapy.

What common side effect does gabapentin cause?

Sedation.

What should be avoided in human gabapentin formulations given to dogs?

Xylitol.