Understanding Analgesics: Opioids, NSAIDs, and Aspirin

Posted on Mar 30, 2025 in Airports

Analgesics are symptomatic medications that decrease the perception of pain without affecting its cause. They are broadly divided into:

Opioid Analgesics

These act centrally (in the CNS) to alleviate severe pain.

Non-Opioid Analgesics

These act peripherally (in the PNS) and are often used in dental pathologies.

Further Classification of Non-Opioid Analgesics:

  • NSAIDs (Non-Steroidal Anti-Inflammatory Drugs): These have anti-inflammatory properties.
  • Antipyretics: These have antipyretic action and little to no anti-inflammatory activity.

Mechanism of Action of NSAIDs

NSAIDs exert their analgesic and anti-inflammatory effects by inhibiting the synthesis of prostaglandins, which are key mediators of pain and inflammation. They inhibit cyclooxygenase, an enzyme that transforms arachidonic acid into thromboxanes and prostaglandins.

The analgesic activity of NSAIDs is moderate, less potent than that of opioid analgesics. They are useful for toothaches, joint pain, muscle pain, and headaches of various etiologies.

Fever can result from infection, tissue damage, inflammation, malignancy, or other disease processes. Prostaglandins contribute to the rise in body temperature. NSAIDs suppress this response.

Indications for NSAIDs

NSAIDs are indicated for the treatment of mild to moderate pain.

Adverse Effects of NSAIDs

  • Gastrointestinal:
    • Gastritis
    • Heartburn
    • Diarrhea
    • Constipation
    • Dyspepsia (poor digestion)

    Chronic treatment can cause erosions and ulcers in the gastric and duodenal mucosa.

  • Renal Toxicity: Prolonged use can cause renal toxicity.
  • Hypersensitivity
  • Hematologic Reactions

Acetylsalicylic Acid (Aspirin)

Properties of Aspirin:

  1. Analgesic and Antipyretic Action: Effective in doses of 0.5 to 2 grams orally.
  2. Anti-inflammatory Action: Effective in doses from 3 grams every 24 hours.
  3. Antiplatelet Action: Even small doses inhibit platelet cyclooxygenase. Aspirin is not recommended before or after dental procedures.
  4. Effect on Uric Acid Excretion:
    • Low doses (1 gram/24 hours) inhibit secretion.
    • High doses (more than 3 grams/24 hours) promote secretion.

Pharmacokinetics of Aspirin:

  • Aspirin is absorbed in the stomach and the first part of the duodenum.
  • It has rapid distribution and high protein binding capacity (80%).
  • It can displace other weak acidic substances that share the same binding sites, such as antivitamin K.

Metabolism of Aspirin:

Aspirin has a short half-life of 15 minutes and is rapidly hydrolyzed into:

  1. Salicylic Acid
  2. Acetic Acid

Presentation and Dosage of Aspirin:

  • Children: 50mg per kilogram every 24 hours.
  • Adults: 1 gram every 24 hours.

Presentation Forms:

  • Effervescent Tablets
  • Soluble Powder
  • Injectable Solution

Aspirin is also associated with other active ingredients in medications like Dolmen, Coludina, and Fiorinal.

Undesirable Effects of Aspirin:

  1. Gastric Irritation and Bleeding: Risk of aggravation of peptic ulcers.
  2. Allergic Manifestations:
    • Erythema
    • Urticaria
    • Anaphylactic Shock
  3. Blood Dyscrasias: Due to antiplatelet action, aspirin can be used for the prevention of thrombosis, cardiovascular accidents, and behavioral disorders.
  4. Hemolytic Anemia
  5. Overdose Symptoms:
    • Vertigo and tinnitus
    • Respiratory problems
    • Dehydration, convulsions, and coma