Pain (pharm)

Question 1

Types of Pain

Answer 1

1. Nociceptive: somatic and visceral secondary to actual tissue damage
2. Neuropathic: central/peripheral nervous system, chronic pain initiated by nervous system
3. Mixed

Question 2

Acetaminophen MOA

Answer 2

-Inhibits prostaglandin COX-3 synthesis in CNS
-Non inflammatory, antipyretic and analgesic
-Role in nociceptive pain, can be combined with opioids
-Caution: hepatotoxic (kicker disease, chronic ETOH max)
-Limit 4 grams daily
-Good for chronic pain such as arthritis

Question 3

NSAIDs MOA

Answer 3

-Inhibits prostaglandin (COX-1 and or COX-2)
-anti-inflammatory, analgesic, antipyretic
-COX-2 selective or non-selective inhibitors
-Role in nociceptive pain
-Mono therapy for inflammatory conditions such as osteoarthritis, RA, bursitis, tendonitis, gout, low back pain
-Combination with opioid can be sparing
-COX 1 maintains stomach lining

-S/E: nausea, dyspepsia, , ulcers, erosions, GERD, GI bleeding, renal toxicity, hypertension, peripheral edema, CHF, thrombosis-platelet effects, allergies (ASA-sensitive bronchospams in asthmatics, rashes-SJS/vasculitis)

-Highest risk of GI bleeds: ketorolac and diclofenac
-Low risk: celecoxib due to selective only COX-2

Question 4

RX muscle relaxants

Answer 4

-Cyclobenzaprine
-Baclofen
-Tizanidine
-Methocarbamol
-Most benefit in the first 1-2 weeks
-Start low, increase slowly and taper off

Question 5

Opioids key notes

Answer 5

-Stronger sufentanil-> fentanyl-> hydromorphone->oxycodone->morphine->codeine

-MEQ or MEDD to evaluate/compare total opioid intake in morphine amount
-Incomplete cross tolerance 25-50% reduction when switching to different opioid

-CNCP regime 70-80% in long acting and 20-25% in short acting (decrease or similar amount of opioids)

-Palliative all in long acting +added BT (generally q1h) on top 10-15% of total scheduled dose (increase opioid amounts)

Question 6

Opioids side effects

Answer 6

-constipation managed with stimulants or PEG/lactulose
-Nausea can be managed with gravel or maxeran etc
-Sedation reduce and eliminate other sedating meds
-Endocrine abnormalities such as hypogonadism may require hormone supplementation
-Opioid induced hyperalgesia
-Opioid withdrawal issues

Question 7

Opioid withdrawal issues

Answer 7

-Red flags: not using as directed, use for non-pain reasons, multi-source, escalating doses
-Withdrawal: pain, sweating, pupil changes, tachycardia, diarrhea, anxiety

Question 7

Opioid induce hyperalgesia

Answer 7

-Increase sensitivity to pain stimuli
-Worsening of pain despite increasing dosing of opioids
-Pain more diffuse and extending beyond the pre-existing pain area
-Pain elicited from ordinary non-painful stimuli
-Hypersensitization

Question 8

General tapering of opioids

Answer 8

-Community: 10% decrease of original dose at every 1-3 weeks
-How fast? two ways 1. dose reduction 2. speed of reduction
-Slow taper by 50% ice the patient reaches 30% of original dose

Question 9

Anticonvulsants (gabapentin and pregablin)

Answer 9

-Gabapentin (Neurontin) and prcegablin (Lyrica) MOA: poorly understood, suppression of dorsal horn activity

Question 10

Anticonvulsant (carbamazepine)
-FOR ALL anticonvulsant taper slowly even in absence of seizure history
-Anti-epileptics can worsen the mood

Answer 10

-Carbamazepine (Tegretol): MOA reduction of glutamate neurotransmitter, blocking sodium channel in brain, enhance the GAGA nergic activity
-Recommended for trigeminal neuralgia (severe facial pain)

Question 11

Anticonvulsant (Topiramate)

Answer 11

-Topiramate (Topamax): migraine prophylaxis
-Significant S/E: renal calculi, metabolic acidosis, weight loss, skin rash

Question 12

TCA MOA

Answer 12

MOA: inhibit reuptake of serotonin and norepinephrine as well some effects on NDMA receptors

TCA: nortriptyline (better choice due to less sedation and other side effects are less) and amitriptyline (way more sedating), avoid in TCA for renal impairment

Question 13

SNRI-serotonin norepinephrine reuptake inhibitors MOA

Answer 13

MOA: inhibit reuptake of serotonin and norepinephrine in synaptic cleft

SNRI (Venlafaxine and duloxetine: similar in terms of side effects), avoid duloxetine in hepatic impairment

Question 14

Triptains (5 HT receptor antagonists) MOA

Answer 14

MOA: works on vascular hypothesis, inhibits calcitonin gene related petite which is thought to increase trigeminal nerve pain

-Take early within 30 min of onset
-If combined with other serotonergic agents (serotonin syndrome)

Question 15

Migraine treatment

Answer 15

-Acute: triptans and NSAIDS
-Prophylaxis: anticonvulsants (lamotrigine, divalproex, topiramate), beta blockers (propranolol), TCA