Analgesics and Opioids Overview

Analgesics

• Analgesics are used to relieve pain.
• Narcotic analgesics (opioids) are strong pain relievers.
• Non-narcotic analgesics (antipyretics) reduce fever and pain.

Types of Opioids

• Endogenous opioids include endorphins, enkephalins, and dynorphins.
• Plant alkaloids like morphine, codeine, and thebaine are extracted from plants.
• Semisynthetic opioids are modified versions of natural opioids.
• Synthetic opioids are completely man-made. Examples: diamorphine (heroin), oxycodone, hydromorphone, buprenorphine, pethidine, methadone, fentanyl, tramadol, and pentazocine.

Pharmacology of Opioids

• Opioids bind to specific receptors in the central nervous system (CNS) and other tissues.
• Opioid receptors are G-protein-coupled receptors.
• Types of opioid receptors include delta, kappa, and mu receptors.

Pharmacological Actions of Opioids

• Desirable: analgesia (pain relief), sedation (calmness), antitussive (cough suppression).
• Undesirable: nausea/vomiting, respiratory depression, mental clouding, and confusion.

Therapeutic Indications of Opioids

• Pain (severe cases)
• Anxiety (sedative effects)
• Cough (sometimes codeine)
• Diarrhea (opium only)

Opioids Dependence

• Tolerance: increased dose needed for the same effect after repeated use.
• Addiction: compulsive drug use due to psychological attachment to the drug's effects.
• Physical Dependence: developing withdrawal syndrome after cessation of drug use or administration of an opioid antagonist.

Opioid Withdrawal Syndrome

• CNS stimulation
• Tachypnea
• Tachycardia and hypertension
• Severe flu-like symptoms
• Yawning, lacrimation, diaphoresis
• Nausea, vomiting, diarrhea
• Abdominal and leg cramping

Opioid Antagonists

• Opioid antagonists, such as naloxone, are used to reverse opioid overdose.
• Naloxone is a competitive opioid receptor antagonist, meaning it competes with opioids for receptor binding.

Acute Opioid Toxicity

• Mild: pinpoint pupils, hypoventilation, hypotension, bradycardia, flaccid muscles
• Severe: severe respiratory depression leading to arrest, severe cardiovascular depression, seizures, and coma.

Antipyretics

• Antipyretics are medications that reduce fever.
• Cyclooxygenase (COX) enzymes are involved in fever and inflammation.

Types of Antipyretics

• Nonsteroidal anti-inflammatory drugs (NSAIDs) include acetylsalicylic acid (aspirin), ibuprofen, and naproxen.
• Acetaminophen (paracetamol)

Acetylsalicylic Acid (ASA)

• Mechanism: Irreversibly inhibits COX-1 and COX-2.
• Uses: Pain relief, fever reduction, anti-platelet effects.
• Adverse effects: Bleeding, GI upset, and Bronchial asthma.
• Risks: Risk of Reye's syndrome in children.

Acetaminophen (Paracetamol)

• Mechanism: Inhibits COX enzyme activity.
• Uses: Pain relief and fever reduction.
• Adverse effects: liver damage if taken in high doses

OTC Drugs

• OTC drugs (Over-the-Counter) are medications available without a prescription at drugstores or supermarkets.
• General characteristics: safe with recommended doses, limited toxicity with self-limiting symptoms, and effective (but possibly less potent than prescription).

Cold Preparations

• Antihistamines: reduce allergy symptoms by blocking histamine receptors.
• Decongestants: constrict nasal blood vessels to relieve congestion.
• Antitussives: reduce coughing.
• Expectorants: loosen mucus for easier expulsion.

Expectorants

• Mechanism: increase volume and reduce viscosity of bronchial secretions, allowing cilia to expel loosened secretions.
• Indications: productive coughs.

OTC Anti-Ulcer Drugs

• Antacids
• H2 blockers
• Proton pump inhibitors (PPIs)

Drug Interactions

• Combining certain OTC drugs with other medications can lead to adverse effects.
• Many OTC and prescription drugs can interact causing unintended consequences or making each other less effective.

Peptic Ulcer and H. Pylori

• Helicobacter pylori (H. pylori) is a gram-negative bacterium associated with peptic ulcer disease.
• Treatment options (to eradicate H. pylori): Triple therapy, Quadruple therapy