Drug interactions/prescribing Flashcards
(21 cards)
Give 5 risk factors for drug interactions related to the patient
- Polypharmacy
- Old age
- Genetics
- Renal disease
- Hepatic disease
Give 3 risk factors for drug interactions related to properties of the drug
- Steep dose/response curve
- Saturable metabolism (paracetamol, alcohol)
- Narrow therapeutic index
Give 5 ways that absorption of a drug can be altered
- Motility of GI drug (OCP + antibiotics ^ GM)
- Acidity of the stomach (antacids and Amprenavir)
- Solubility (avacado and anticoagulant)
- Complex formation (chelates - tetracycline and dairy products)
- Action on enterocytes (Grapefruit juice)
How does protein binding affect drugs?
If patient unwell, will often have low albumin levels. If this happens then there will be less protein binding so an increased plasma concentration of drug, eg. antibiotics
How does an inhibitor work?
Drug A blocks metabolism of Drug B, leaving more Drug B in the plasma. Increased effects
How does an inducer work?
Drug C induces CYP450 isoenzyme leading to increased metabolism of Drug D so a decreased therapeutic effect
Could grapefruit juice have any positive effects on drug taking?
Grapefruit juice will increase the bioavailability of the drug, meaning that in third world countries, if taking cyclosporin for kidney transplant, would be taken in conjunction with grapefruit juice to increase effects
If a patient had become intoxicated with a weakly acidic drug (ibuprofen), what could you do to their urine to speed up clearance?
Make more alkaline
Give an example of a partial agonist that could be given to wean a patient off hard drugs
Subutex (buprenorphine)
What is the danger of combining diazepam and alcohol?
Both sedatives @ GABA receptor –> death
Why should you query the use of beta blockers in diabetics?
- Blocking B3 receptor affects blood glucose control (which is already poor)
- Blocking B2 receptor suppresses hypoglycaemic awareness
What is the INR of a drug?
International normalised ratio - Time taken for blood to clot. Higher the INR longer it will take to clot
Is there an issue with combining NSAID’s and ACE- inhibitors
ACE inhibitors are used as hypertension medication. NSAID’s can both:
- increase sodium retention, increasing blood pressure
- inhibit the action of renal prostaglandins which promote vasodilation
What happens if digoxin and furosemide are combined?
Digoxin works on cardiac fibres (used in treatment of heart conditions eg. AF) . Its effects are increased if low K+ levels in plasma. Furosemide = diuretic that lowers arterial pressure but favours loss of K+ meaning toxicity of digoxin increases
When prescribing simvastatin for cholesterol what other drugs must you be aware that the patient is not on? If these drugs are administered together what is the outcome?
Antibiotics (eg. erythromycin, clarithromycin) antifungals (itraconozole), Ca channel blockers (dilitiazem, verapamil) or antiarrhythmics (amiodarone).
Outcome would be rhabdomyolysis
What drugs could increase the chances of bleeds with warfarin?
Antibiotics (erythromycin, clarithromycin), opiods (tramadol) or antiarrhythmic (amiodarone)
What is known as the ‘triple whammy’?
ACE inhibitor + NSAIDs/COX -2 inhibitor +dehydration / furosemide.
This leads to renal failure
SSRI’s (anti-depressant) prescribed with what increase the risk of developing serotonin syndrome?
Tricyclic antidepressants or tramadol (opioid)
What is the biggest error in prescribing paracetamol and penicillin?
Many other drugs include them
- Paracetamol (co-…-amol)
- Penicillin (Tazocin, Augmentin (amoxicillin)
–> toxic levels administered
KNOW WHAT IS IN WHAT YOU’RE PRESCRIBING
Give the insulin suffixes for rapid acting, short acting and intermediate acting insulin and the names for long acting.
Rapid- Log (<15 mins)
Short - Lin R (0.5 - 1 hour)
Intermediate - Lin N (2-4 hours)
Long - Glargine (Lantus) and Detemir (Levemir)
In cancer treatment of children, vincristine and methotextrate are administered simultaneously. By what routes?
Vincristine = IV Methotextrate = Intrathecal
