Pharmacology & Analgesia Flashcards
What are the route of administration for drugs?
- Intravenous (fastest)
- Intramuscular
- Intrathecal
- Oral
- Rectal
- Local effect (topical)
- Subcutaneous
- Sublingual/suppository
- Transdermal
What is pharmacokinetics?
Movement/concentration of drugs in the body
What is pharmacodynamics?
Effects of drugs & mechanism of their actions
What are the 3 methods of elimination of drugs?
- Biliary (gall bladder)
- Intestinal
- Renal
What is the fraction unabsorbed (Fu)?
Fraction of medication that does not get absorbed - goes straight into gut & excreted out
What is the process of pharmokinetics?
- Administration
- Absorption
- Distribution (bloodstream/tissues)
- Metabolism (liver)
- Elimination
What are the two points of action of analgesics?
- Inflammatory pain (peripheral nociceptors)
- Tissue damage or CNS pain (neuropathic pain)
What tissues can be affected by analgesics?
- Peripheral tissues
- Peripheral nerve fibres
- Dorsal horn of spinal cord
- Key brain sites
What does the inhibition of cyclooxygenase (COX2 inhibitors) cause?
- Limited CNS effect
- Inhibit central sensitisation - Major peripheral effect
- Inhibit leukocytes
- Decrease cytokines
- Inhibit platelet aggregation, free radicals
What is the simple analgesic for pain?
Paracetamol: Inhibits prostaglandins at hypothalamus & spine
What is the simple analgesic for inflammation & pain?
Aspirin: NSAIDs, COX2 inhibitors
What is the simple analgesic for muscle spasm?
Diazepan, benzodiazepine (valium)
What are the risks of NSAIDs?
- Nausea, heartburn, indigestion
- Gastric bleeding
- Increase risk of CV events by 1/3
- Doubles risk of heart failure
- High doses linked to increase risk of GI complications
What are the risk factors for problems with NSAIDs?
- Certain medications (blood thinners, corticosteroids)
- Medical conditions (gastric ulcer/bleeding, high BP, diabetes)
- > 65 years
- Taking another NSAID a the same time
- Alcohol
- Taking more than recommended dose
- Taking more than a few days at a time
What is the function of opioids?
Act act opioid receptors in PNS & CNS, cause relaxation/calming
What are the side effects of opioids?
- Nausea
- Vomiting
- Itching
- Constipation
- Respiratory depression
What are examples of opioids?
- Codiene
- Fentanyl
- Morphine
- Oxycodone
What is the function of local anaesthetic?
- Few hours of pain relief
- Infiltration (peppering) of region around joint/tooth
- E.g. nerve block to reset dislocated fingers
What is the function of regional anaesthesia?
- Spinal: Single shot into fluid surrounding spinal cord
- Epidural: Catheter
- Peripheral nerve block: Femoral, sciatic, subsartorius, can be single shot or catheter
What is the function of general anaesthesia?
- Temporarily unconscious
- Paralysed & sedated
- Intubated for breathing
- IV or inhalation
What is the function of an epidural?
- Delivers anaesthetic by catheter slowly & can cover a long period of time
- Causes paralysis of muscles, but patient still awake
- Delivered to epidural space outside dural, spreads throughout tissues
- Respiratory complications, dural puncture
What is the function of a spinal block?
- Single shot
- Small fine needle through dura into cerebrospinal fluid
- Short-term cover
What are the physio implications of epidural and spinal block?
Patient cannot mobilise until epidural is removed & muscle strength has returned
What are the indications for the use of a femoral nerve block?
Surgery of anterior thigh & knee, e.g. TKA
What are the functions of femoral nerve blocks?
- Reduce requirements for opioids
- Decrease adverse side effects from opioids
What are the complications of femoral nerve blocks?
- Nerve injury (rare)
- Risk of falls
What muscles are affected by femoral nerve block?
- Iliacus
- Sartorius
- Pectineus
- Quads
What is the function of a saphenous nerve block?
Numbs distal thigh, knee, lower leg, spares quads
What are some of the drugs used for PCA?
- Morphine
- Fentanyl
- Tramadol
What are some of the multimodal analgesics?
- Epidural
- GA + periarticular + PCA
- GA + femoral nerve block
- GA + periarticular + ice
