PSA: prescription review Flashcards
dosing methotrexate
Rheumatology: dose range 5-25mg once weekly
Gastroenterology: Starting dose – 25mg once weekly for 16 weeks
Maintenance dose – 15mg once weekly
Always prescribe methotrexate in multiples of the 2.5mg tablet strength
what are the most common cytochrome p450 inducers. what does this mean?
increased enzyme activity –> decreased drug concentration as it is metabolised quickly
PC BRAS
Phenytoin
Carbamazepine
Barbituates
Rifampicin
Alcohol (chronic excess)
Sulphonylureas
what are the most common cytochrome p450 inhibitors. what does this mean?
decreased enzyme activity –> increased drug concentrations as not metabolsied quickly
AODEVICES
Allopurinol
Omeprazole
Disulfiram
Erythromycin
Valproate
Isoniazid
Ciprofloxacin
Ethanol (Acute intoxication)
Sulfonamides
what antibiotic is contraindicated with methotrexate?
trimethoprim
how does ibruprofen cause aki
inhibits prostaglandin synthesis –> reduces renal artery diameter (and blood flow) and therefore causes reduced perfusion
can also cause AIN
how does rampiril cuase aki?
decreases angiotensin 2 which is responsible for preserving eGFR
what is the impact of diuretics on sodium?
all diuretics can cause hyponautraemia,
although when they contribute to dehydration, sodium may increase causing hypernautraemia
what electrolyte derangement do thiazide diuretics cuase
hypokalameia
what electrolyte derangement foes ACEi cause?
hyperkalaemia
what electrolyte derangement do loop diuretics cause
hypokalaemia
what analgesics to avoid in asthma
nsaids
most common SE amlodipine
ankle oedema
(clue = echo normal)
interactions between calcium channels and beta blockers?
non-dihydropyridine CCBs such as dilatizem and verapamil are contraindicated due to the risk of severe bradycardia and LV failure. This is because non-dihydropyridine calcium channel blockers slow conduction at the SA and AV nodes.
The dihydropyridine calcium channel blockers (amlodipine, nifedipine, lercanidipine) are safe to take with beta-blockers as they are primarily peripheral vasodilators.
what drugs may cause fourniers gangrene
SGLT2 inhibitors eg dapagliflozin
pregnancy and chloramphenicol
can cause the potentially fatal severe reaction - grey baby syndrome
avoid all forms (topical and oral)
what drugs should be stopped in aki
rampiril
metformin
what diabetes drug doesn’t have a risk of hypoglycaemia
metformin
in metabolic acidosis, which drug should be held
metformin
Metformin itself can cause lactic acidosis, and as a result, if a patient is in a state of metabolic acidosis it should be held whilst the acidosis is corrected.
common reasons that drugs that are contraindicated in severe renal impairment?
narrow therapeutic range and therefore accumulate eg lithium
Damage to kidneys –> aki
drugs causing hyponautraemia
inreased sodium out
- diuretics
increased water in…
“SIADH cannot void”
SSRIs (eg sertraline) and sulphonylureas (eg gliclazide)
Indomethacin and Inhibitors (ACEi and PPI)
Antidepressants (eg tricyclics)
Diuretics
Haloperidol
Cannot: cyclophosphamide, carbamazepine
Void: vincristine
hypnotics (such as temazepam)
dosing sertraline depression
Initially 50 mg once daily,
then increased in steps of 50 mg at intervals of at least 1 week if required; maintenance 50 mg once daily; maximum 200 mg per day.
features seretonin syndrome
Neuromuscular excitation
hyperreflexia
myoclonus
rigidity
autonomic nervous system excitation
hyperthermia
sweating
altered mental state
Confusion
causes seretonin syndrome
antidepressants: SSRI, SNRI, TCA, MAOI
Drugs causing SS esp when interacting with others:
- lithium
- tramadol, pethidine
- St John’s Wort
recreational:
- ecstasy
- amphetamines
management seretonin syndrome
supportive including IV fluids
benzodiazepines
more severe cases are managed using serotonin antagonists such as cyproheptadine and chlorpromazine
elderly patient on antidepressant, dosing error?
some antidepressants eg escitalopram, have a lower dose for elderly patients
escitalopram should be given at a maximum dose of 10mg per day for elderly patients.
if a pt on lithium has levels <04 what do you do?
- check complicance
- consider factors that may affect plasma lithium levels (e.g. excess fluid intake, drug interactions, brand change)
+ increase the dose slightly eg by 100mg
typical lithium starting dose
Lithium 400mg ON
what change to medications do you need to make, addisons and infection
double dose of hydrocortisone
what abs is CI during treatment of overactive bladder with botulism toxin
gentamicin
what anti-diabeties drug is CI in bladder cancer
Pioglitazone is associated with a small increased risk of bladder cancer and is contraindicated in patients with active bladder cancer or a past history of bladder cancer.
what drugs are prescribed in micrograms and therefore can be a massive prescribing error if done in mg
FFLAND
Folic acid
Fludrocortisone
Levothyroxine
Atropine
Digoxin
Naloxone
adverse effect hydroxycloriquine
Long-term use of hydroxychloroquine can lead to retinopathy known as ‘Bull’s eye maculopathy’. Common symptoms include central vision loss (central scotoma), change in color vision and visual distortions.
dosing atorvostatin
priamary prevention 20mg
secondary prevention 80mg
why is cyclizine not reccomended in the elderly
Cyclizine has anticholinergic properties, which is why regular use is not recommended, particularly in the elderly. Agitation is a rare side effect, most commonly observed at higher doses.
clarithromycin plus atorvastatin equals
Macrolide antibiotics such as clarithromycin and erythromycin act to increase the side effects of statins such as atorvastatin. A rare side effect is rhabdomyolysis (muscle breakdown) which results in an elevation of creatine kinase released from the damaged muscle.
what drugs affect the haemodynamics and therefore can cause renal aki
NSAIDs cause afferent vasoconstriction
ACEi and ARBs cause efferent vasodilation
These reduce the pressure gradient and therefore reduce eGFR
what drugs are nephrotoxic
Acute tubular necrosis causing drugs: (AVRG)
Aminoglycosides
Vancomycin
Radio contrast
Gentamicin
Acute interstitial nephritis causing drugs: (PPN)
PPI
Penicillin
NSAID
what drugs should you hold during aki
DAMN
Diuretics
ACEi/ARB/Antibiotics esp aminoglycosides
Metformin, lithium, digoxin, opiates (narrow TW) (may have to be stopped)
NSAIDs
why do you soemtimes stop metformin in aki
increased risk of toxicity (but doesn’t usually worsen AKI itself)
what drugs should be stopped around the time of surgery?
I LACK OP
Insulin
Lithium
Anticoagulants/antiplatelets
COCP/HRT
K-sparing diuretics
Oral hypoglycaemics
Perindopril and other ACEi
when should COCP/HRT be stopped - surgery
4w before
when should lithium be stopped - surgery
day before
when should potassium sparing diuretics amd ACEi be stopped - surgery
day of surgery
safety considerations NSAIDS
NSAIDS
No urine (ie renal fialure/aki)
Systolic dysfucntion (ie heart failure)
Asthma
Indigestion
Dyscrasia (clotting abnormality)
diabetes medications and surgery
NBM therefore metformin stopped - risk of lactic acidosis
other oral hypoglycaemics can cause hypoglucaemia so these are stopped too
sliding scale should be started whereby hourly blood glucose monitoring adjusts the hourly dose of insulin
corticosteroids and surgery
at induction of anaestehsia, give iv steroids
if on long term corticosteroids as these pts often ahve adrenal atrophy therefore wont be able to mount a big enough stress response to surgery
sick day rules steroids
double the dose
if a pt is on paracetamol, what should you check
DOSE!!! look for co-codamol co-prescribed etc
trap paracetamol max dosing
if pt <50kg, max dose is 500mg 6 hourly !!!
alendronic acid prescription
10mg od or 70mg weekly
when to withold antihypertensives
when hypotensive, aki, cold peripheries etc
causes of oral candidiasis drugs
steroids
abx
immunocompromised
drugs which increase risk of falls
benzos
antidep - particualrly TCA and SNRI
MAOI
antipsychotics
opiates
antihypertensives
