Pharm, Therapeutics, Toxic 8 Flashcards
Drugs to avoid when BREASTFEEDING?
- Abx: tetracycline, ciprofloxacin, chloramphenicol
- psych: BZDs, lithium, clozapine
- Aspirin
- Amiodarone
- Carbimazole
- Cytotoxics
- Methotrexate
- Sulphonylureas
Drugs considered safe if breastfeeding?
- Abx: penicillin, trimethoprim, cephalosporins
- psych: TCAs, antipsychotics
- asthma: salbutamol, theopyllines
- endo: thyroxine, glucocorticoid (avoid high dose)
- epilepsy: valproate, carbamazepine
- CVS: warfarin, heparin, digoxin, beta-blockers, hydralazine
Breastfeeding C/Is?
- drugs
- viral infections
- galactosaemia
Mechanism of Evolocumab and where is it used?
- prevents PCSK9-mediated LDL receptor degradation by binding to PCSK9 and preventing circulating PCSK9 from binding to LDL-Rs on liver cell surface, therefore preventing their degradation
- increasing liver LDLR results in ass reductions in serum LDL-cholesterol
- use of evolocumab ass with reduced free PCSK9 (measure of target engagement)
- dosage 140mg / 2 wks
- specialist prescription, if LDL-C > 3.5 persistently
MoA of Fibrates
- increase lipoprotein lipase activity via PPAR-alpha agonism
MoA of Ezetimibe
- reduces intestinal absorption of cholesterol
Anaesthetic agent with features of:
- rapid onset of anaesthesia
- pain on IV injection
- rapidly metabolised with little accumulation of metabolites
- anti-emetic properties
- moderate myocardial depression
- widely used esp for maintaining sedation on ITU, total IV anaesthesia and for daycase surgery
PROPOFOL
Anaesthetic agent with features of:
- extremely rapid onset so agent of choice for rapid sequence induction
- marked myocardial depression may occur
- metabolites build up quickly
- unsuitable for maintenance infusion
- little analgesic effects
SODIUM THIOPENTONE
Anaesthetic agent with features of:
- mod-strong analgesic properties
- may be used for induction of anaesthesia
- produces little myocardial depression (so suitable agent if pt not haemodynamically stable)
- may induce state of dissociative anaesthesia -> nightmares
- can be used in neuropathoc pain porrly responsive to titrated opioids & oral adjuvant analgesics eg antidepressant/convulsant, esp when there is abnormal pain sensitivity eg allodynia, hyperalgesia, hyperpathia
KETAMINE
Anaesthetic agent with features of:
- favourable cardiac safety profile with v little haemodynamic instability
- no analgesic properties
- unsuitable for maintaining sedation as prolonged (and even brief) use may result in adrenal suppression
- post-op vomiting common
ETOMIDATE
MoA of Ketamine?
NMDA-receptor antagonist
MoA of Gabapentin?
Modulates voltage-gated calcium channel
3 main features of serotonin syndrome?
- neuromuscular excitation (hyperreflexia, myoclonus, rigidity etc)
- ANS excitation e.g. hyperthermia
- altered mental state
Rx of serotonin syndrome:
- 1st line?
- if more severe?
IVI + BZD
- if more severe can use serotonin antagonist e.g. cyproheptadine & chlorpromazine
Examples of serotonin antagonists?
cyproheptadine & chlorpromazine
4 Drugs that can cause of serotonin syndrome?
MAO-inhibitors
SSRIs
ecstasy
amphetamines
Acute Rx of caustic/corrosive substance ingestion?
ABCDE - esp caution airway, look for peri-peal oedema
- high dose IV PPI
- urgent upper GI surgical referral if signs of perforation (e.g. surgical emphysema, CXR mediastinal widening)
- AVOID neutralisation -> exothermic rxn -> further injury
If Sx -> urgent OGDto assess degree of ulceration (Zargar classification), if extensive injury on OGD consider urgent surgical exploration
If ASx -> observe & trial oral fluid
Acute & Chronic complications of caustic/corrosive substance ingestions?
Acute:
- upper GI ulceration, perforation
- upper airway injury & compromise
- aspiration pneumonitis
- infection
- electrolyte disturbance e.g. hypocalcaemia in hydrofluoric acid ingestion
Chronic:
- strictures, fistulae, gastric outlet obstruction
- upper GI carcinoma (inc risk 1000-3000x)
Mechanism of action of Class Ia anti-arrthymics?
3 Examples?
Sodium channel blockers
- increases AP duration
quinidine
procainamide
disopyramide
Mechanism of action of Class Ib anti-arrthymics?
3 Examples?
Sodium channel blockers
- decreases AP duration
lidocaine
mexiletine
tocainide
Mechanism of action of Class Ic anti-arrthymics?
3 examples?
Sodium channel blockers
- no effect on AP duration
flecainide
encainide
propafenone
Mechanism of action of Class II anti-arrthymics?
examples?
Beta-blockers
propranolol
atenolol
bisoprolol
metoprolol
Mechanism of action of Class III anti-arrthymics?
examples?
Potassium channel blockers
amiodarone
sotalol
ibutilide
bretylium
Mechanism of action of Class IV anti-arrthymics?
examples?
Calcium channel blockers
verapamil
diltiazem
Therapeutic range of lithium?
when to take the sample?
0.4-1.0
12h post-dose
toxicity tends to occur > 1.5
When to take levels of ciclosporin?
Trough levels immediately before dose
When to take levels of digoxin?
At least 6hours post-dose
When to take levels of phenytoin if monitoring is required?
When would you consider monitoring phenytoin levels?
Trough levels immediately before dose
- adjusted phenytoin dose
- suspected toxicity
- detection of non-adherence to prescribed meds
Taking Abx whilst on the COCP - do they reduce efficacy?
No extra precaution required for contraception
Except for Abx which are enzyme inducers i.e. rifampicin & rifaximin (& other enzyme inducers)
What are phase I reactions in drug metabolism?
Oxidation, reduction, hydrolysis
- mainly by p450 enzymes, but also e.g. etoh dehydrogenase, xanthine oxidase
- phase I products typically more active & potentially toxic
What are phase II reactions in drug metabolism?
Conjugation
- products typically inactive & excreted in urine/bile
What does zero-order kinetics describe in drug metabolism?
Metabolism that is independent of the concentration of reactant
- pathways become saturated -> constant amount of drug being eliminated per unit time
4 drugs which exhibit zero-order kinetics?
phenytoin
heparin
ETOH
salicylates - high-dose aspirin
What does acetylator status mean?
Which 5 drugs are affected by acetylator status?
50% UK population are deficient in hepatic N-acetyletransferase
- isoniazid
- procainamide
- hydralazine
- sulfasalazine
- dapsone
‘slow acetylators’ are more likely to suffer hepatitixicity
What is meant by high first-pass metabolism?
Examples of drugs
Where a drug’s concentration is greatly reduced by hepatic metabolism before it reaches the systemic circulation, so much larger doses are needed orally than by other routes
aspirin ISDN GTN propranolol verapamil lignocaine isoprenaline hydrocortisone testosterone
What is mechanism of action of digoxin and it’s uses?
- decreases conduction through the AV node (slows ventricular rate in AF & flutter)
- +ive inotrope: inhibits Na/K ATPase pump, increasing force of cardiac muscle contraction (Sx relief in heart failure)
- stimulates the vagus nerve
Features of digoxin toxicity?
Rx?
- generally unwell, lethargy, nausea & vomit, anorexia, confusion, yellow-green vision
- arrhythmias e.g. AV block, bradycardia
- gynaecomastia
- Correct arrhythmias
- Monitor K+
- Digibind if necessary
Likelihood of toxicity increases progressively when digoxin level rises, progressively, from 1.5-3
Factors that precipitate digoxin toxicity? pt factors electrolytes/bloods comorbidities drugs
Pt: increasing age, hypothermia
Blds: low K, low Mg, high Na, high Ca, low albumin, acidosis
PMH/status: renal failure, myocardial ischaemia, hypothyroidism
Drugs: - amiodarone - verapamil - diltiazem - spironolactone - ciclosporin - quinidine & drugs which cause hypokalaemia etc
MoA of heparin?
LMWH?
unfractionated?
Activates antithrombin III
LMWH: increases action of antithrombin III on factor Xa
unfractionated heparin: forms a complex which inhibits thrombin & factors IXa, Xa, XIa, XIIa.
Difference between SC LMWH & unfractionated IV heparin:
duration?
monitoring?
LMWH has long duration of action, standard unfractionated is short
LMWH - anti-factor Xa if monitoring required
standard IV heparin - monitor APTT (this heparin is useful if high risk bleeding as can be monitored, and anticoag can be terminated rapidly)
4 Side-effects of heparin
- bleeding
- HIThrombocytopenia
- osteoporosis
- hyperkalaemia (inhibition of aldosterone secretion)
LMWH has lower risk of HIT & osteoporosis
Rx for heparin overdose
protamine sulphate (only partially reverses effects of lmwh)
How is heparin-induced thrombocytopenia mediated?
when does it usually develop?
what are 3 features?
Rx options?
Immune-mediated: Ab form against PF4 (platelet factor 4) & heparin complexes
- > these Ab bind to these complexes on platelet surface
- > induce platelet activation by cross-linking FcgammaIIA receptors
- develops after 5-10days of Rx
- pro-thrombotic
- Rx options inc: alternative anticoagulants e.g. lepirudin & danaparoid
- > 50% reduction in platelets
- thrombosis
- skin allergy
What is acute intermittent porphyria?
How does it usually present?
Autosomal dominant condition caused by defect in porphobilinogen deaminase (haem biosynthesis affected)
- abdo & neuropsych Sx in 20-40yrs olds, 5x more common in females
Drugs which may precipitate an attack of acute intermittent porphyria?
- etoh, OCP
- BZD, barbiturates
- halothane, sulphonamides
4 commonest drug causes of urticaria?
aspirin
nsaids
penicillins
opiates
Drugs which are known to cause impaired glucose tolerance?
- steroids
- ciclosporin, tacrolimus
- thiazides, furosemide (less common)
- IFN-alpha
- nicotinic acid
- atypical antipsychotics e.g. olanzapine
- beta-blockers - caution in diabetics as they can interfere with metabolic & autonomic responses to hypoglycaemia
Drugs that can cause photosensitivity?
- thiazides
- amiodarone
- nsaids e.g. piroxicam
- psoralens
- sulfonylureas
- tetracyclines, sulphonamides, ciprofloxacin
How do quinolones work? what is their MoA?
what are mechanisms of resistance?
Inhibit DNA synthesis and are bactericidal
- inhibit topoisomeras II (DNA gyrase) & IV
mechanisms of resistance: mutations to DNA gyrase, efflux pumps which reduce intracellular quinolone concentration
5 Adverse/side effects of quinolone?
- lower seizure threshold in epilepsy
- tendon damage/rupture (increased if pt on steroids; idiosyncratic)
- lengthen QT interval
- P450 enzyme Inhibitor!
- can provoke a haemolytic crisis in g6pd deficiency
quinolone generally avoided in children due to uncertain risk of cartilage damage
Why does carbon monoxide cause a left-shift of the o2 dissociation curve & tissue hypoxia?
What are the features?
What is Rx & indication?
- has high affinity for Hb & myoglobin
- headache 90%
- nausea & vomiting; vertigo 50%
- confusion 30%
- subjective weakness 20%
- severe: ‘pink’ skin & mucosa, hyperpyrexia, arrhythmias, extrapyramidal features, coma, death
Rx = 100% O2 Hyperbaric O2 are indicated if: - LOC at any point - neuro signs at any point - myocardial ischaemia/arrhythmia - pregnancy
CarboxyHb levels: <3% non-smoker <10% smokers 10-30% Sc: headache, vomiting >30% severe toxicity
What is mechanism of action of Cyclosporin?
Indications?
Adverse effects? (‘increased’)
Calcineurin inhibitor immunosuppressant
Binds to form a complex with cyclophilin -> inhibits calcineurin -> inhibits activation of various transcription factors in T cells
- decreases T cell clonal proliferation by reducing IL-2 release
- after organ Tx
- RA, psoriasis (direct effect on keratinocytes, & modulates T cell function)
- UC
- pure red cell aplasia
- nephrotoxic, hepatotoxic
- fluid retention, HTN
- hyperkalaemia, hyperlipidaemia, impaired glucose tolerance
- tremor, gingival hyperplasia, hypertrichosis
- increased susceptibility to severe infection
When to give Acetylcysteine in presumed paracetamol overdose?? (3)
How is it given?
- Staggered OD (taken over >1hr)
- Unknown/doubt in time of ingestion
- If plasma conc above the Rx line from 4hours (100) to 15h (15)
Give IV over 1hour to reduce number of adverse effects
King’s College criteria for Liver Tx in paracetamol-induced liver failure?
arterial pH < 7.3, 24h after ingestion or all of the following: - PT > 100 - Cr > 300 - grade III/IV encephalopathy
Drug causes of thrombocytopenia?
- NSAIDs, heparin
- furosemide
- penicillins, sulphonamides, rifampicin
- carbamazepine, valproate
- quinine
- abciximab
Causes of low Mg?
Features?
Rx?
- ETOH, diarrhoea
- diuretics
- low K, low Ca
- TPM
- conditions ass with diarrhoea e.g. IBD
- metabolic disorders: Gitelmans, Bartters
Features:
- tetany, paraesthesia
- arrhythmias, seizures
- decreased PTH secretion -> low Ca
- ECG features similar to hypokalaemia
- exacerbates digoxin toxicity
Rx:
> 0.4 oral 10-20mmol/d but diarrhoea common
< 0.4 IV e.g. 40mmol/24h
What is Trastuzumab?
Adverse effects?
Herceptin
= mAb directed against HER2/neu receptor
- flu-like sx & diarrhoea common
- Cardiotoxic: Echo monitoring done inc before Rx. More common when anthracyclines also used
Features of beta-blocker OD?
Rx?
If resistant?
- bradycardia, hypotension, syncope, heart failure
- Atropine if bradycardia
- Glucagon if resistant (+ve inotrope & decreases renal vascular resistance)
- Cardiac pacing if unresponsive to pharm Rx
Adrenaline:
what does it do physiologically?
Actions on alpha adrenergic receptors?
beta?
- released by adrenal glands, acts on alpha 1/2 & beta 1/2 receptors
- increases TPR & cardiac output
- causes vasoconstriction in skin & kidneys -> narrow pulse pressure
- it induces hyperglycemia, hyperlactatemia & hypokalaemia
Alpha:
- inhibits pancreatic insulin secretion
- stimulates glycogenolysis in lover & muscle
- stimulates glycolysis in muscle
Beta:
- stimulates pancreatic glucagon secretion
- stimulates ACTH
- stimulates lipolysis by adipose tissue
Rx of accidental injection of adrenaline?
Local infiltration of Phentolamine
P450 enzyme inducers?
- phenytoin, carbamazepine
- phenobarbitone
- rifampicin
- chronic etoh
- griseofulvin
- st Johns wort
- smoking (affects CYP1A2)
P450 enzyme inhibitors?
- ciprofloxacin, erythromycin
- simetidine, omeprazole
- isoniazid
- amiodarone
- allopurinol
- ketoconazole, fluconazole
- fluoxetine, sertraline
- valproate
- acute etoh
- ritonavir
- quinupristin
Serotonin 5-HT receptor agonist examples
Sumatriptan 5-HT1D agonist (acute migraine Rx)
Ergotamine partial 5-HT1 agonist
Serotonin 5-HT receptor antagonist examples
Pizotifen = 5HT-2 antagonist (migraine prophylaxis) Cyproheptadine = 5HT-2 antagonist (diarrhoea in carcinoid syndrome) Ondansetron = 5HT-3 antagonist (anti-emetic)
Acid-base balance in salicylate OD?
Mixed resp alkalosis & metabolic acidosis
- early stimulation of resp centre -> rest alkalosis
- direct acid + acute renal failure -> acidosis
Features of salicylate OD?
- lethargy, sweating, fever
- nausea, vomiting
- tinnitus
- hyperventilation
- hypo & hyperglycaemia
- seizures, coma
Rx of salicylate OD?
What are the indications for haemodialysis?
- ABCDE, charcoal
- Urinary alkalisation with IV sodium bicarbonate (enhances urine elimination of aspirin)
HD indications:
- serum conc > 700
- resistant metabolic acidosis
- acute renal failure
- pulmonary oedema
- seizures, coma
Features of tricyclic OD:
early?
severe?
ECG changes?
Early (anticholinergic):
- dry mouth
- agitation, sinus tachycardia
- blurred vision, dilated pupils
Severe (esp amitriptyline, dosulepin):
- arrhythmias, seizures, metabolic acidosis, coma
ECG:
- sinus tachycardia
- QRS widening (>100 ass with inc risk seizures, >160 ass with ventricular arrhythmias)
- prolongation of QT interval
Rx of tricyclic OD?
- IV Bicarbonate to correct acidosis is 1st line* It may reduce seizure & arrhythmia risk
- IV lipid emulsion can be used to bind free drug & reduce toxicity
- class Ia Ic & III anti-arrhythmics are C/I
Rifampicin:
MoA?
side-effects?
- inhibits bacterial DNA dependent RNA poymerase, preventing transcription of DNA -> mRNA
- flu-like Sx, orange secretions
- hepatitis, enzyme inducer
Isoniazid:
MoA?
side-effects?
- inhibits mycelia acid synthesis
- peripheral neuropathy (give pyridoxine/vit B6)
- hepatitis, agranulocytosis
- enzyme inhibitor
- psychosis
Pyrazinamide:
MoA?
side-effects?
- converted by pyrazinamidase into pyrazinoic acid -> inhibits fatty acid synthase I
- hyperuricaemia -> gout
- arthralgia, myalgia
- hepatitis
Ethambutol:
MoA?
side-effects?
- inhibits enzyme arabinosyl transferase which polymerises arabinose into arabinan
- optic neuritis (check acuity before & during Rx)
- rash
- dose adjustment required in renal impairment
Features of stages of toxicity of ethylene glycol/antifreeze?
Rx?
- Sx similar to xs etoh: confusion, slurred speech, dizziness
- tachycardia, hypotension, metabolic acidosis with raised anion gap & high osmolar gap
- acute renal failure
FOMEPIZOLE (etoh dehydrogenase inhibitor)
HD if refractory
Which Abx inhibit cell wall formation?
peptidoglycan X-linking: penicillins, cephalosporins, carbopenems
peptidoglycan synthesis: glycopeptides e.g. vancomycin
Which Abx inhibit protein synthesis?
50S subunit: macrolides, chloramphenicol, clindamycin, linezolid, streptogrammins
30S subunit: aminoglycosides, tetracyclines
Which Abx inhibit DNA synthesis?
quinolones
Which Abx damages DNA?
metronidazole
Which Abx inhibit folic acid formation?
sulphonamides
trimethoprim
Which Abx inhibits RNA synthesis?
rifampicin
Why does cyanide lead to poisoning?
What are the features?
Rx?
- from reversible inhibition of cellular oxidising enzymes (cytochrome c oxidase) leading to cessation of mitochondrial electron transfer chain -> cells can’t make ATP -> histotoxic hypoxia
classical: brick-red skin, smell of bitter almonds
acute: hypoxia, hypotension, headache, confusion
chronic: ataxia, peripheral neuropathy, dermatitis
- high lactate, metabolic acidosis
100% O2
IV Hydroxocobalamin
can also use combo from: amyl nitrite inh, sodium nitrite iv, sodium thiosulfate iv
GHB can cause what life-threatening feature?
Resp depression, esp when taken with e.g. etch
Rx of motion sickness
Hyoscine (most effective but side-effects)
> Cyclizine > promethazine