Clinical Pharmacology And Toxicology Flashcards
(55 cards)
in carbon monoxide poisoning the oxygen saturation of haemoglobin decreases leading to an early plateau in the oxygen dissociation curve
in 2008, the Department of Health publication ‘Recognising Carbon Monoxide Poisoning’ also listed loss of consciousness at any point, neurological signs other than headache, myocardial ischaemia or arrhythmia and pregnancy as indications for hyperbaric oxygen
P450 system inducers ; results in faster metabolism of the drugs resulting in reduced efficacy
Induction usually requires prolonged exposure to the inducing drug, as opposed to P450 inhibitors, where effects are often seen rapidly
Inducers of the P450 system include
antiepileptics: phenytoin, carbamazepine
barbiturates: phenobarbitone
rifampicin
St John’s Wort
chronic alcohol intake
griseofulvin
smoking (affects CYP1A2, reason why smokers require more aminophylline)
Inhibitors of the P450 system include: result in prolonged action of the medicines
antibiotics: ciprofloxacin, erythromycin
isoniazid
cimetidine,omeprazole
amiodarone
allopurinol
imidazoles: ketoconazole, fluconazole
SSRIs: fluoxetine, sertraline
ritonavir
sodium valproate
acute alcohol intake
quinupristin
Quinolones (e.g. ciprofloxacin) - inhibits DNA synthesis
Inhibit bacterial DNA duplication through inhibition of topoisomerase
Causes of drug-induced photosensitivity
thiazides
tetracyclines, sulphonamides, ciprofloxacin
amiodarone
NSAIDs e.g. piroxicam
psoralens
sulphonylureas
fomepizole acts as a competitive inhibitor of alcohol dehydrogenase.
Alcohol dehydrogenase is the primary enzyme responsible for metabolising ethylene glycol into its toxic metabolites, including glycoaldehyde and glycolic acid. By competitively inhibiting this enzyme, fomepizole prevents the formation of these harmful substances and allows the body to excrete unmetabolised ethylene glycol via renal elimination.
Metformin should be titrated slowly, leave at least 1 week before increasing dose
When using metformin immediate-release medication the BNF advises that the dose is initially 500 mg once daily for at least 1 week, and then increased 500 mg twice daily for at least 1 week. This is because a common side effect of metformin is diarrhoea and this can be worse if it is increased too soon.
If using modified-release preparations then the BNF advises that the dose increased gradually, every 10-15 days
Digoxin toxicity Ix ;
if toxicity is suspected, digoxin concentrations should be measured within 8 to 12 hours of the last dose
is a monoclonal antibody directed against the HER2/neu receptor. It is used mainly in metastatic breast cancer
Trastuzumab (Herceptin)
although some patients with early disease are now also given trastuzumab.
Severe lithium toxicity is an indication for haemodialysis
> 2.5 mmol/L
It has a very narrow therapeutic range (0.4-1.0 mmol/L) and a long plasma half-life being excreted primarily by the kidneys. Lithium toxicity generally occurs following concentrations > 1.5 mmol/L.
Early endoscopy and risk stratification is important in patients with symptomatic caustic ingestion
Drugs that can be cleared with haemodialysis - mnemonic: BLAST
Haemodialysis in overdose
Barbiturate
Lithium
Alcohol (inc methanol, ethylene glycol)
Salicylates
Theophyllines (charcoal haemoperfusion is preferable)
Drugs which cannot be cleared with haemodialysis include
tricyclics
benzodiazepines
dextropropoxyphene (Co-proxamol)
digoxin
beta-blockers
This has been established by studies like the Cardiac Arrhythmia Suppression Trial (CAST) which found an increased risk of death or nonfatal cardiac arrest in post-myocardial infarction patients treated with class IC antiarrhythmics.
Flecainaide
*****syndrome presents with a triad of extensive skin rash, high fever, and organ involvement
DRESS
Common drugs causing DRESS include allopurinol, anti-epileptics, antibiotics, immunosuppresants, HIV treatment and NSAIDS.
Patients at a high risk of severe cutaneous adverse reaction should be screened for the
HLA-B *5801 allele.
Avoidance of using hypotonic (0.45%) in paediatric patients - risk of hyponatraemic encephalopathy
A 15-year-old boy is reviewed. He has been referred by his GP with ptosis, diplopia and night blindness. On examination he is noted to have a degree of ophthalmoplegia, bilateral partial ptosis and evidence of retinitis pigmentosa during fundoscopy. His mother developed a similar problem when she was 18-years-old. What is the most likely diagnosis?
Kearns-Sayre syndrome
mitochondrial inheritance
onset < 20-years-old
external ophthalmoplegia
retinitis pigmentosa
REM sleep is associated with dreaming and loss of muscle tone
N1 → N2 → N3 → REM
Theta → Sleep spindles/K-complexes → Delta → Beta
The Sleep Doctor’s Brain
Contrast MRI scan is the gold standard investigation for cerebral metastases - provided no contraindications
Correlation studies
parametric (normally distributed): Pearson’s coefficient
non-parametric: Spearman’s coefficient
