Basics of prescribing Flashcards
Which drugs are P450 inducers?
Phenytoin
Carbamazepine
Barbituates
Rifampicin
Alcohol (chronic abuse)
Sulphonylureas
Which drugs are P450 inhibitors?
AO DEVICES
Allopurinol
Omeprazole
Disulfiram
Erythromycin
Valproate
Isoniazide
Ciprofloxacin
Ethanol (acute intoxication)
Sulphonamides
What is the PReSCRIBER mnemonic?
The mnemonic used for prescribing checks of drugs.
Patient details
Reactions
Sign front of chart
Contraindications
Route of drug
IV fluid if needed
Blood clot prophylaxis
anti-Emetic if needed
Relief if needed of pain
What are the side effects of steroid medications?
“STEROIDS”
Stomach ulcer
Thin skin
oEdema
Right and left heart failure
Osteoporosis
Infection
Diabetes
cushings Syndrome
Safety consideration of NSAID’s?
No urine
Systolic dysfunction
Asthma
Indigestion
Dyscrasia (clotting abnormality)
How do you choose which fluid replacement to presscribe?
Give all patients 0.9% saline unless they are hypernatraemic or hypoglycaemic (5% dextrose instead).
Has ascites: give human albumin solution instead as it maintains oncotic pressure.
Haemorrhagic shock: give blood transfusion but a crystalloid first if no blood available.
Common side effects of Thiazide diuretics?
Gout
Hypokalaemia
Common side effects of Spiranolactone?
Hyperkalaemia
Gynaecomastia
Common side effects of diuretics in general?
Renal failure. Prescribe with caution.
When would you give a STAT infusion of 500ml 0.9% saline?
To a patient whom was haemodynamically unstable
- Tachycardic
- Hypotensive
You would give 250ml in this situation to a patient with heart failure.
In what situation would you give a patient 1L fluid over 2-4 hours? (0.9% saline)
A patient whom was oliguric.
How can you roughly predict the level of fluid depletion in a patient using basic observations?
500ml depleted: reduced urine output <30ml/hr
1L depleted: olguric and tachycardic
> 2L: reduced urine output, tachycardic and shocked.
What is the maximum rate in which potassium can be infused?
Potassium should not be infused at a faster rate than 10mmol/hour.
What are the general fluid requirements of a patient in 24 hours?
Adults 3L IV fluid
Elderly 2L IV fluid
What is a basic fluid regime for a patient?
“1 salty 2 sweet”
1L of 0.9% saline and 2L of 5% dextrose
How much potassium does a patient require each dayt?
Around 40mmol/L a day (put 20mmol of KCl/day in 2 bags)
What is the prophylactic dose of LMWH?
5000 units
When should metocloperamide be avoided?
In patients with Parkinsons disease
In young women as it increases the risk of dyskinesias
Which anti-emetic is best for patients with heart failure?
Metocloperamide 10mg 8 hourly IM/IV
What is the first line treatment for patients with neuropathic pain?
Amitryptilline or Pregabalin
Which weight threshold means that you reduce paracetamol dose?
Body weight of 50kg
Some side effects (including neurological) of anti-muscarinic drugs
Eg. Oxybutynin
Increased confusion, pupillary dilation with loss of accommodation, dry mouth and tachycardia (after transient bradycardia)
Which drugs should not be taken/used with caution alongside methotrexate?
Methotrexate can cause renal impairment so any medications that can lead to this same outcome should be used with caution.
What are the consequences of using calcium channel blockers and beta blockers together?
They are both rate limiting drugs so can therefore result in a
- bradycardia
- asystole
- hypotension
Causes of hypernatraemia?
All begin with a D
- Dehydration
- Drips
- Drugs - effervescent tablets with a high sodium content
- Diabetes insipidus
What are the causes of microcytic anaemia?
Thalassaemia
Anaemia of chronic disease
Iron deficiency anaemia
Lead poisoning
Sideroblastic anaemia
What are the causes of normocytic anaemia?
Anaemia of chronic disease
Acute blood loss
Haemolytic anaemia
Renal failure (chronic)
What are the causes of macrocytic anaemia?
B12/folate deficiency
Excess alcohol
Liver disease
Hypothyroidism
Haemotological diseases beginning with an M - ‘Megaloblastic’, ‘Myeloproliferative’, ‘Myelodysplastic’, ‘Multiple myeloma’.
What are the causes for high neutrophils?
Bacterial infection
Tissue damage
Steroids
What are the causes for low neutrophils?
Viral infection
Chemotherapy
Clozapine
Carbimazole
What are the causes for high lymphocytes?
Viral infection
Lymphoma
Chronic lymphocytic leukaemia
What are the causes of low platelets?
Reduced production or increased destruction
Reduced production - drugs, malignancies, infection (usually viral)
Increased destruction - Heparin, hypersplenism, DIC
What are the causes of high platelets?
Reactive during bleeding, tissue damage, postsplenectomy and malignancies
How do you split the different causes of hyponatraemia?
Hypovolaemic
Euvolaemic
Hypervolaemic
What are the hypovolaemic causes for hyponatraemia?
Fluid loss (especially diarrhoea and vomiting)
Addison’s disease
Diuretics (any type)
What are the euvolaemic causes of hyponatraemia?
Syndrome of inappropriate antidiuretic hormone (SIADH)
Psychogenic polydipsia
Hypothyroidism
What are the causes of hypervolaemic hyponatraemia?
Heart failure and renal failure are the most common causes
What are the causes of hypokalaemia?
DIRE
Drugs (loop and thiazide diuretics)
Inadequate intake or intestinal loss (diarrhoea/vomiting)
Renal tubular acidosis
Endocrine (Cushing’s and Conn’s syndrome)
What are the causes of hyperkalaemia?
DREAD
Drugs (potassium sparing diuretics and ACE inhibitors)
Renal failure
Endocrine (Addison’s disease)
Artefact (very common due to clotted sample)
DKA (note that when insulin is given to treat DKA the potassium drops, requiring regular (hourly) monitoring +/- replacement
If a patient has a raised urea with a normal creatinine and unaffected/unchanged eGFR, what is this likely to indicate?
You should check the haemoglobin as the patient has likely had an UGIB.
What are some of the features of Digoxin toxicity?
Confusion
Nausea
Visual halos
Arrythmias
What are some of the signs of Lithium toxicity?
Tremor (coarse)
Oliguria
X - ataXia
I - Increased reflexes
C - confusion, coma, decreased consciousness
What are some of the signs of phenytoin toxicity?
Gum hypertrophy
Ataxia
Nystagmus
Peripheral neuropathy
Teratogenicity
What are some of the side effects from Gentamicin and Vancomycin toxicity?
Nephrotoxicity and Ototoxicity
Important side effect of carbamazepine?
Can cause hyponatraemia
