Act on
specific receptor sites in the CNS that are concerned with pain perception
Narcotics – a
drug which will induce sleep as well as relieve pain
May induce dependence
if given in the absence of pain
Do not induce
dependence if given in pain
Discovered in
the opium poppy
Has an
affinity for a number of opioid receptors
mu
receptor - analgesia delta
receptor - respiratory depression
kappa - sedation sigma
-
hallucinations
Naloxone is an opioid antagonist and may
reverse the effects of morphine
May reduce
coughing and thicken bronchial secretions
Produces mental
detachment and euphoria which helps to reduce anxiety so may enhance analgesia
High doses
usually causes pinpoint pupils
Tolerance
develops
10 – 20 mg Fast or
slow routs of administration
Fentanyl (sublimase) Dextromoramide (palfium) Dihydrocodeine (DF 118)
Pethidine
Codeine
Does not harm
gastric mucosa Is not
anti-inflammatory 0.5
– 1 g 4 – 6
hourly
May cause hepatonecrotic damage in acute overdose
Antidotes are
effective if within 10 – 12 hours of ingestion
Chronic use of
several mild analgesics may cause renal damage
Compound
analgesics are probably useless so combine paracetamol or aspirin with a full
dose of the opioid component
Damages cell
membranes release fatty acids
These are converted
to prostaglandins by the enzyme cyclo-oxygenase
Prostaglandins
are inflammatory mediators
NSAIDs inhibit
the action of cyclo-oxygenase
Contra-indicated
in peptic ulceration Gastric
irritation and bleeding
Nausea and
vomiting Worsening
of asthma
Hypersensitivity Do
not give if patient is sensitive to aspirin
May be highly
protein bound so interact with anticoagulants
Different
patients respond differently to the various NSAID preparations, the occurrence
of side effects is one of the main choice criteria
Pain
associated with inflammation
Full
anti-inflammatory effects may take up to 3 weeks to develop
NASIDs are palliative – they do not effect the underlying disease process
Examples -
Ibuprofen, naproxen, diclofenac, indometacin, nabumetone
Acetylsalicylic
acid Discovered in
300 – 600 mg 4 hourly Inhibits
cyclo-oxygenase
Gastric
irritation and bleeding Give soluble preparations with food
Asthma Hypersensitivity
Hyperventilation,
dizziness, confusion, tinnitus, deafness, hypothrombinaemia, respiratory and
cardiovascular complications from acid base disturbance
Haemodialysis
may be needed
May occur in
children
Acute
encephalopathy and fatty degeneration of the liver
Never give
aspirin to the under 12s
Antiplatlet Anti-inflammatory Antipyretic
Regulation of
impulses through the substantia gelatinosa from peripheral fibres to the spinal
transmitter cells which carries the impulse up to the brain.
Endorphin
receptors are also involved