Pharmacology of Analgesics

Analgesics Pharmacology

• Analgesics are medications that reduce pain.
• Two major groups of analgesics: anti-inflammatory analgesics and opioid analgesics.

Anti-inflammatory Analgesics

• These drugs reduce inflammation at the pain site.
• Examples include: acetaminophen, aspirin, COX-2 inhibitors, and NSAIDs (such as ibuprofen and naproxen).
• NSAIDs work by blocking cyclo-oxygenase (COX) enzymes. COX enzymes create prostaglandins. Prostaglandins control various processes, including inflammation, blood flow, and blood clot formation.
• Nonselective NSAIDs inhibit both COX-1 and COX-2. Selective NSAIDs (COX-2 inhibitors) primarily inhibit COX-2, reducing gastrointestinal side effects but possibly increasing cardiovascular risk.
• Aspirin is an NSAID that, in small doses, reduces the risk of heart attacks and strokes.
• Acetaminophen primarily inhibits brain COX, is good for mild to moderate pain, and is generally well-tolerated.

Opioid Analgesics

• Also called narcotics, they change the brain's perception of pain.
• Examples include: morphine, codeine, fentanyl, hydrocodone, meperidine, methadone, naloxone, and naltrexone.
• Opioid analgesics work on three major receptor classes: μ, δ, and κ.
• Each receptor has endogenous ligands like endorphin (μ) and dynorphin (κ).
• μ, κ, and δ receptors modulate pain perception.
• μ receptors have subtypes (μ1 and μ2).
• δ receptors have subtypes (δ1 and δ2).
• κ receptors have subtypes (κ1, κ2, and κ3).
• Activation of opioid receptors affects nociceptive transmission in the following ways:
  • Inhibits calcium influx into presynaptic terminals to reduce neurotransmitter release.
  • Opens potassium channels to hyperpolarize postsynaptic neurons, making them less responsive.
• Common side effects of opioid analgesics include euphoria, dysphoria, sedation, respiratory depression, constipation, suppression of endocrine systems, cardiovascular issues (like bradycardia), convulsions, nausea, vomiting, pruritus (itching), and miosis (pinpoint pupils).
• Repeated exposure to opioids can lead to tolerance, requiring higher doses for the same analgesic effect.

Cautions and Contraindications

• Opioid analgesics should be used with caution in patients with bronchial asthma, heavy pulmonary secretions, convulsive disorders, biliary obstruction, head injuries, and a history of allergies to the drugs.
• Opioid analgesics should also be used with caution in elderly patients and pregnant women.

This quiz explores the pharmacology of analgesics, focusing on both anti-inflammatory and opioid analgesics. Learn about different medications, their functions, and the mechanisms behind pain relief. Test your knowledge on NSAIDs, COX inhibitors, and the role of opioids in pain management.