Page 49 Guide to Pain Management in Low-Resource Settings

Pharmacology of Analgesics (Excluding Opioids) 37

• Still, comparing the unwanted drug side effects in serious pain, but not as a means to decrease
of all analgesic compounds, including opiates, daily discomfort; only then is their use mean-
one would come to the conclusion that they ingful and justifiable.
all have their problems. They should be used

Table 3
Major side eff ects, drug interactions, and contradictions of COX inhibitors
Adverse Drug
Drug Reactions* Drug Interactions Contradictions (Absolute and Relative)
Nonselective, Acidic Drugs
Aspirin Inhibition of platelet Vitamin K antagonists Hypersensitivity to the active substance or to any of the
aggregation for days, excipients, impaired blood coagulation, pregnancy and all
aspirin-induced asthma, contradictions listed below
ulcerations, bleeds
Diclofenac GI ulcerations, dys- ACE inhibitors, glucocor- Asthma, acute rhinitis, nasal polyps, angioedema, urti-
Ibuprofen pepsia, increased BP, ticoids, diuretics, lithium, caria or other allergic-type reactions after taking ASA or
Indomethacin water retention, allergic SSRIs, ibuprofen: reduction NSAIDs; active peptic ulceration or GI bleeds; infl am-
Ketoprofen (asthmatic) reactions, of low-dose aspirin cardio- matory bowel disease; established ischemic heart disease,
Ketorolac vertigo, tinnitus protection peripheral arterial disease and/or cerebrovascular disease;
Naproxen renal failure
Meloxicam
Selective (Preferential) COX-2 Inhibitors
Acetaminophen Liver damage Not prominent Liver damage, alcohol abuse
(paracetamol)
Celecoxib Allergic reactions (sul- Blocks CYP2D6; interac- Existing pronounced atherosclerosis, renal failure
fonamide) tions with SSRIs and beta-
blockers
Etoricoxib Water retention, in- Reduces estrogen metabo- As with celecoxib, plus insuffi cient control of blood pres-
creased blood pressure lism sure; cardiac insuffi ciency
* More pronounced in highly potent and/or slowly eliminated drugs (all except ibuprofen)

Table 4
Pharmacokinetic data on non-COX, nonopioid analgesics
Type (Drug) t Common Dosing Adverse Reactions
50
Antiepileptics
Carbamazepine ~2 days ~0.5 g b.i.d. 1 Diplopia, ataxia (aplastic anemia)

Gabapentin ~6 hours ~1 g b.i.d. Somnolence, dizziness, ataxia, headache, tremor
Pregabalin ~5 hours ~200 mg t.i.d.
Blockers of NMDA-receptor Na -channels
+
Ketamine (race- Fast, ~50 mg/d 0.5 mg/kg/h Hypersalivation, hypertension, tachycardia, bad dreams
2
mic)
+
+
S -Ketamine As racemic, comp. S -
ketamine, twice as active
N-Type Ca-Channel Blockers 3
Ziconotide Permanent intrathecal CNS disturbances from nausea to coma depending on the dose
administration and distribution of the toxin, granuloma-formation
1 No hard evidence for analgesic eff ects aside of trigeminal neuralgia; no dose recommendations for neuropathic pain available.
2 Ketamine is highly lipophilic and sequesters into fat tissue (t , distribution ~ 20 min); continuous infusion requires attention (to avoid
50
overdosing).
3 Only in desperate patients if intrathecal administration is possible.