Pharmacology - Pain and drug reactions Flashcards
What are the different pain types?
Acute (nociceptive)
Cancer
Neuropathic (nerve pain)
Chronic non cancer (pain 3+ months, fibromyalgia)
Medications acting on gate controlled pathway?
NSAIDS, opioids, Local anaesthesia
What is step 1,2 & 3 on the pain ladder for pain meds?
Step 1 = Paracetamol / NSAID
Step 2 = Weak opioid (Codeine, tramadol)
Step 3 = stronger opioid (Morphine, Fentanyl, Methadone, Oxycodone)
What acronym is used for Adverse drug reactions?
ABCDSs (Rawlin Thompsons)
What does ABCDE stand for and mean?
Augmented (common) = is this presentation predictable
Bizarre (odd) - is there a history of allergy
Chronic - Has patient used drug for long time
Delayed - has patient used drug in past (could cause the issue now?)
End of use - Is patient withdrawing
Where are all adverse drug reactions reported?
Reported by MHRA YELLOW CARD SCHEME
Patient factors affecting drug interactions?
Old
Polypharmacy
Genetics
hepato/renal disease
What are drug factors?
Narrow therapeutic index, solubility
Examples of drug with small therapeutic window?
Digoxin
Very small therapeutic window
slight overdose can be very bad news
What is therapeutic range?
Where drug is effective
above or below this is negative
Pharmacokinetics influences drug action by influencing?
ADME
what is absorption affected by?
Acidity (Eg. using PPI)
Motility (eg. erythromycin increases GI motility, OCP + Abx interact therefore gut motility changes and affect contraceptive function)
Solubility
What is distribution affected by?
Protein binding
What is metabolism affected by?
CYP450 Induction (low therapeutic effect) eg. alcohol, St Johns wort
CYP450 Inhibition (high therapeutic effect) eg. erythromycin, grape juice
What is excretion affected by?
Urine pH
Acids cleared faster if urine weakly basic
Bases clear faster is urine weakly acidic
What are some naturally occurring opioids?
Morphine + Codeine
Modified opioid ?
Diamorphine (heroin)
twice as strong as morphine - man made
Oral Bioavailability?
50%
Potency of morphine, diamorphine and pethidine for same effect?
5mg diamorphine
10mg morphine
100mg Pethidine (10x weaker than morphine)
The receptors for these opioids are found where?
In CNS + GIT + resp centres (pontine)
Use of opioids?
analgesia (strong)
Side effects of opioids?
Addiction
GI - Constipation & N+V
Resp - Resp distress/depression
Treatment for opioid induces resp depression?
Naloxone (Competitive opioid inhibitor)
What is tolerance vs dependance?
Tolerance = Due to overstimulation of opioid receptor - desensitisation
higher dose required to achieve same effect
Dependence = Psychological state of craving euphoria (dependent on it)
