Anti-Inflammatory Medications and Pain Relief

Anti-Inflammatory Medications and Pain Relief

• Anti-inflammatory medications are used to treat pain and inflammation.
• Inflammation is the body's response to injury or infection.
• Cardinal signs of inflammation are pain, heat, redness, and swelling.
• Damaged cells release chemicals that initiate the inflammatory cascade.
• This cascade increases blood flow to the damaged area.

Inflammatory Cascade

• The inflammatory cascade is initiated when phospholipids in the cell membrane are broken down by phospholipase.
• This process forms arachidonic acid and enzymes released by the body during tissue damage.
• Key factors in this process are lipoxygenase and cyclooxygenase inhibition.

Types of Pain

• Visceral pain: Pain originating from internal organs or the lining of organs (e.g., thorax, pelvis, pleura, abdomen).
• Somatic pain: Pain in the musculoskeletal tissues on the surface of the body; usually reduced by rest, and aggravated by activity.
• Neuropathic pain: Pain caused by injury or damage to the spinal cord or peripheral nerves; commonly occurs at the site of injury or below it.

Cyclooxygenase (COX)

• Pain from inflammation results from the enzyme cyclooxygenase (COX).
• COX-1 is continuously produced in the body, ensuring prostaglandins are maintained at constant levels.
• COX-2 is only formed when an inflammatory response occurs in response to tissue injury.
• Both COX-1 and COX-2 convert arachidonic acid into prostaglandins, causing pain and inflammation.
• Nonsteroidal anti-inflammatory drugs (NSAIDs) selectively inhibit COX-2, only.

Anti-Inflammatory Medications

• Corticosteroids: Hormones produced by the adrenal cortex. Synthetic replications are used to treat inflammation, and are grouped into mineralocorticoids and glucocorticoids.
  • Mineralocorticoids (e.g., aldosterone): naturally occurring hormones that help retain water and sodium (important for healing).
  • Glucocorticoids (e.g., cortisol): help treat inflammation and suppress the immune system; synthetic forms are widely utilized in veterinary medicine.
• Antihistamines: Block the binding of histamine to H1 or H2 receptors and inhibit the inflammatory process. H1 blockers treat allergic reactions and anaphylactic shock, while H2 blockers suppress gastric secretions, aiding in stomach function.

Pain Management: Opioids

• Opioids can be used as anesthetics and analgesics; they are classified according to the type of effect they produce.
  • Agonists: Bind closely to receptors and produce desired responses.
  • Partial agonists: Bind similarly to agonists but produce a smaller response.
  • Antagonists: Prevent biological responses; they don't create a desired opioid effect.
  • Mixed agonists/antagonists: Result in a varied or inconsistent effect.
• Opioid receptors are mu, kappa, delta, and opioid receptor-like-1 (ORL-1).

Local and Topical Anesthetics

• Work by numbing the intended site directly.
• Used during nerve blocks, to numb areas such as the eyes, ears, and larynx.
• Common examples include bupivacaine; lidocaine; marcaine; mepivacaine; procaine; and tetracaine.

Nonsteroidal Anti-inflammatory Drugs (NSAIDs)

• Alleviate pain and inflammation by interfering with the inflammatory cascade.
• Decrease inflammation after surgery or trauma and greatly enhance analgesia, often in forms of pain relief.
• Inhibit COX enzymes which reduce prostaglandin production.
• COX-2 inhibition is key, with COX-2 inhibition promoting effectiveness of the drug.
• COX-1 inhibition leads to some unwanted side effects like gastrointestinal upset.

NSAID Advantages and Adverse Effects

• Advantages: Available, long duration of action, low cost, easy administration.
• Adverse effects: Vomiting, gastrointestinal ulceration, bleeding, hepatotoxicity, nephrotoxicity, bone marrow suppression, platelet aggregation reduction, and cartilage metabolism inhibition.

Muscle Relaxants

• Can treat inflammatory reactions in muscle tissue and reduce the severity of muscle spasms.
• Spasmolytics/antispasmodics inhibit nerve impulses or reduce excitability of motor neurons, helping muscle relaxation.
• Neuromuscular blockers stop the transmission of neurotransmitters at neuromuscular junctions.
• Often used in preanesthetic procedures (e.g., Methocarbamol).