Misc agents Flashcards
Regarding allopurinol, which of the following is incorrect?
A It is used as an antiprotzoal agent
B It can cuase an acute attack of gout
C It inhibits the metabolism of anicoagulants
D It should be avoided in patients with renal impairment
D
Explanation
Allopurinol is often the first urate lowering drug used. Its most rational indications are: chronic tophaceous gout, in patients whose 24 urinary uric acid exceeds 600-700mg, when probenocid and sulfinpyrazone cannot be used, recurrent reanl stones and in patients with renal functional impairment.
In patients with chronic kidney disease, the initial dose should not exceed >50mg/d and the titrations should be of 50mg/d
It causes an acute attack of gout early in treatmentt when urate crystals are being withdrawn from the tissues and plasma levels are below normal.
It inhibits the metabolism of anticoagulants and probenocid. Chemtherapeutic agents must be reduced by 75%.
It is used as an antiprotozoal agent
All of the following drugs can cause hyperkalaemia EXCEPT?
A Spironolactone
B Methyldopa
C Potassium supplement
D ACE inhibitor
B
Explanation
Spironolactone is a potassium sparing diuretic. It inhibits aldosterone, thereby decreasing sodium absorption and potassium secretion. ACE inhibitors lead to a decrease in aldosterone levels by suppressing angiotensin II. Methyldopa doesn’t seem to have an effect on potassium.
Extra: for interest only-following a internet search, methyldopa may increase potassium levels in the first month of ingestion. Following the first month, methyldopa does not appear to effect potassium levels
Which drug has a half life of 6 hours?
A Lignocaine
B Atenolol
C Aspirin
D Adenosine
B
Explanation
Adenosine -10s
Aspirin-15-25min
Lignociane-2hrs, and
Note: aspirin is absorbed quickly and rapidly hydrolysed to acetic acid and salicylate. Aspirin has a half life of 15-25min and salicylate has a half life of 3.5-4.5 hrs. The text gives a range of 2-19hrs.
Which of the following is NOT A proposed mechanism of N-Acetylcysteine?
A Induction of NAPQI back to paracetamol
B Decreased glutathione availability and release
C Provision of inorganic nitrate
D Direct binding to NAPQI
B
Explanation
NAC prevents NAPQI induced hepatotoxicity when given within 8 hrs of a paracetamol overdose. NAC ameliorates the clinical course of toxicity. Four possible mechanism are described:
- increased glutathione availability
- direct binding to NAPQI,
- provision of an inorganic substrate and
- the reduction of NAPQI back to paracetamol.
Note: in Katzung it states “that NAC acts as a glutathione substitute, binding the toxic metabolite as it is being produced”
Which of the following DOES NOT have its metabolism inhibited by limiting liver blood flow?
A Trimethoprim
B Verapamil
C Lignocaine
D Propoxyphene
A
Explanation
All the drugs listed below (except trimetoprim) have their metabolism inhibited by limiting blood flow. Other drugs with the same problem include: alprenolol, amitriptyline, imipramine, INH, labetalol, lignociane, morphine, propanolol and meperidine
Note: Some drugs are metabolised so readily that even marked reduction in liver FUNCTION does not significantly prolong their action. However, cardiac disease, by limiting blood flow to the liver, may impair disposition of those drugs whose metabolism is FLOW-limited. These drugs are so readily metabolised by the liver that hepatic clearance is essentially equal to liver blood flow.
Flow dependant elimination- some drugs are cleared very readily by the organ of elimination, so that at any clinically realistic concentration of the drug, most of the drug in the blood perfusing the organ is eliminated on the first pass of the drug through it. The elimination of these drugs will thus depend primarily on the rate of the drug delivery to the organ of elimination. Such drugs are called high extraction drugs since they are almost completely extracted from the blood by the organ. BLOOD FLOW TO THE ORGAN IS THE MAIN DETERMINANT OF DRUG DELIVERY.
Which of the following drugs is most likely to cause methaemoglobinemia in adults?
Note: This question can be asked using a clinical scenario: Bier’s block for a reduction of a wrist fracture develops methaemaglobinaemia-which drug is the likely cause?
A Bupivicaine
B Lignocaine
C Prilocaine
D Amethocaine
C
Explanation
The physical examination of patients with suspected methemoglobinaemia should include examination of the skin and mucous membranes. Physical findings may include the following:
Discoloration of the skin, mucous membranes, and blood (the most striking physical finding)
Cyanosis –
Pallor of the skin or conjunctiva suggests anaemia
Seizures
Coma
Cardiac dysrhythmias (bradyarrhythmia or ventricular dysrhythmia)
Acidosis
Symptoms associated with cardiac and/or neurologic ischemia
Intravenous (IV) methylene blue is the first-line antidote agent. Exchange transfusion and hyperbaric oxygen treatment are second-line options for patients with severe methemoglobinaemia whose condition does not respond to methylene blue or who cannot be treated with methylene blue (e.g. 6GDP deficiency)
Treating a BLUE patient with a BLUE drug!
Extra: In some patients, o-toluidine, a metabolite of prilocaine, may cause methemoglobinemia, which may be treated with methylene blue.
Which of the following drugs can cause alopecia?
A Digoxin
B Heparin
C Verapamil
D Amiodarone
B
Explanation
Alopecia from drugs is a usually reversible diffuse nonscarring hair loss that occurs within days to weeks of starting a new medication or changing the dose.
There are two types of drug-induced hair loss:
Anagen effluvium – shedding of actively growing hairs
Telogen effluvium– shedding of resting, or bulb hairs
Anagen effluvium
Anagen effluvium is usually due to chemotherapeutic drugs and rarely with gold, colchicine or poisoning with arsenic, bismuth, thallium or boric acid
Telogen effluvium
Telogen effluvium is the mechanism of virtually all other medication-induced hair loss. The list of possible drug causes:
anti-coagulants –heparin and warfarin
anti-hypertensives – beta-blockers, ACE inhibitors
hormones – oral contraceptive pill (during/after/changing), hormone replacement therapy, androgens
anticonvulsants – valproic acid 12-28% (dose-dependent), carbamazepine up to 6%, phenytoin
mood stabilizers and antidepressants – most, e.g. lithium 12-19%
others – cimetidine, retinoids, antithyroid drugs, cholesterol lowering drugs, interferons, anti-infective agents, amphetamines, NSAIDS, bromocriptine, levodopa, some antipsychotic and anti-anxiety drugs, rarely amytriptyline
Note: According to an editor’s note: 3 cases of hair loss has been reported following the use of amiodarone. Use this option, not to confuse further but to educate
Which of the following drugs does not cause constipation?
A Codeine
B Digoxin
C Verapamil
D Imipramine
E Chlorpromazine
B
Explanation
Chlorpromazine- may cause constipation due to its anticholinergic effects. Imipramine is a Tricyclic antidepressant-may cause constipation due to its anticholinergic. Verapamil has a more profound effect on gut smooth muscle than the other calcium channel antagonists. It reduces gut motility and causes constipation. Codeine- like all other opioids, causes constipation. Generally opiods causes reduced motility and peristaltic motions, but tone is increased. Digoxin causes diarrhoea.
Which of the following drugs can cause hypoprothrombinemia?
A Cefazolin
B Cefuroxime
C Cefotetan
D Cefaclor
C
Explanation
Cephalosporins that contain a methylthiotetrazolegroup (e.g. cefamandole, moxalactam, cefmetazole, cefotetan, cefoperazone) frequently cause hypoprothrobinaemia. Administration of 10mg vitamin K twice weekly can prevent this.
All of the drugs listed produce similar effects except?
A Hyoscine
B Muscarine
C Acetylcholine
D Methacholine
A
Explanation
Hyoscine is the only anticholinergic drug in this group
A) Hyoscine:
Hyoscine (also known as scopolamine) is an anticholinergic drug. It blocks the action of acetylcholine at muscarinic receptors, leading to effects like sedation, reduced secretions, and anti-motion sickness properties.
B) Muscarine:
Muscarine is a naturally occurring alkaloid that activates muscarinic receptors, mimicking the effects of acetylcholine. This can cause effects like bradycardia, increased secretion, and smooth muscle contraction.
C) Acetylcholine:
Acetylcholine is the natural neurotransmitter that activates both nicotinic and muscarinic receptors. It has a wide range of effects, including slowing the heart rate, stimulating smooth muscle contractions, and promoting glandular secretions.
D) Methacholine:
Methacholine is a synthetic choline ester that acts similarly to acetylcholine but is more resistant to degradation by acetylcholinesterase. It is often used in diagnostic tests to provoke bronchoconstriction, testing for conditions like asthma.
Which drug and side effect are incorrectly matched?
A Ethosuximide and hirsutism
B Phenobarbitol and enzyme induction
C Phenytoin and gum hypertrophy
D Sodiumvalpraote and idiosyncratic hepatic toxicity
C
Explanation
Phenytoin causes gum hyperplasia. In the prescribed texts, it is not clearly stated, but ethosuximide can cause hirsutism
Regarding intracellular signalling, which of the drugs listed below has a different mode of action from the others?
A ACTH
B Insulin
C Glucagon
D PTH
B
Explanation
Insulin mode of action involves tyrosine kinase A. The rest of the drugs involve a secondary mechanism cAMP
Which of the following drugs does not interact with warfarin?
A Benzodiazepine
B Phenobarbitone
C Loop diuretic
D Cepholosporins
A
Explanation
Phenobarbitone is an enzyme inducer thus increasing metabolism of warfarin which will decrease the INR.
<enzyme inducer: CRAP GPs>
- carbamazepine, rifampicin, alcohol (chronic), phenytoin, griseofulvin/ glucocorticioids, phenobarbitone, sulphonylureas / St John wart’s
Cephalosporins decrease bacteria in gut that produce vitamin K which will increase the anticoagulant effect of warfarin and increase the INR
Frusemide would cause dehydration and concentrate clotting factors, hence decreasing INR (decreasing anticoagulant effect)
Regarding Alendronic acid (fosamax), which of the following best describes it’s mechanism of action?
A Decrease in phosphate excretion
B Suppresses the activity of osteoclasts
C Increases calcium bone absorption
D Increases osteoblast activity
B
Explanation
Alendronic acid is a bisphosphonate. Its mechanism of action is selective inhibition of bone resorption. It suppresses the activity of osteoclasts in part via inhibition of farnesyl pyrophosphate synthesis. Clinical application includes: osteoporosis, bony mets and hypercalcaemia. Toxicity: renal failure and adynamic bone.
10mls of 50% glucose contains how much glucose?
A 5g
B 50g
C 500mg
D 50mg
A
Explanation
Glucose Intravenous Infusion BP 50%w/v (25g/50mL)
Therefore 5g/10ml
Extra: 50% glucose solution contains 500mg/ml of glucose per ml of solution. 0.5g/ml. Therefore 10mls equals 5g of glucose.
How many mmols of Sodium does a litre of normal saline contain?
A 154
B 140
C 150
D 145mmol
A
Explanation
Normal saline (0.9% saline solution)
0.9 % NaCl (NSaline) —-> 0.9 g in 100mls —-> 9 g in 1 L moelcular weight of NaCl = 23 + 35 = 58 g (exact: 58.44) 9/58 = 0.155 mol or 155 mmol
9 g of NaCl per litre of water * 154 mmol/L sodium* 154 mmol/L chloride* Osmolality = 308 mosm/L* pH = 5.0
Infusate Infusate Na+Extracellular fluid distribution(mmol per litre) (%)5% Sodium chloride in water 855 3% Sodium chloride in water 513 0.9% Sodium chloride in water 154 Ringer’s lactate solution 130 0.45% Sodium chloride in water 77 0.2% Sodium chloride in water 34
How much sodium is contained in a solution of 8.4% NAHCO3 (sodium bicarbonate)?
A 1mmol/ml
B 3mmol/ml
C 2mmol/ml
D 0.5mmol/ml
A
Explanation
NAHCO3- 84mg/ml
Na- 1mmol/ml
HCO3-1mmol/ml
1:1 ration of Na: HCO3
pH 8.0
Extra: 1mL has a mass of 1g Therefore there is 0.084g of NaHCO3 present in 1mL of this solution. The molar mass of NaHCO3 is 84g/mol-0.084g divided by 84g/mol = 0.001mol or 1mmol. There is 1mmol of NaHCO3 and therefore 1mmol of Na
Which of the following eye drops reduce aqueous humour secretion?
A Timolol
B Latanoprost
C Pilocarpine
D Epinephrine
A
Explanation
Pilocarpine, carbachol, physostigmine, echothiophate, demecarium (cholinomimetics) - ciliary muscle contraction, opening of the trabecular meshwork, increased outflow
Brmonidine, Apraclonidine (alpha2 selective agonist) - decreased aqueous secretion
Epinephrine, dipivefrin (non selective alpha agonist) -increased outflow
Timolol, betaxolol, carteolol, levobunolol, metipranolol (beta blockers) -decreased aqueous secretion from the ciliary epithelium
Acetazolamide, dichlorphenamide, methazolamide, dorzolamide, brinzolamide (carbonic anhydrase inhibitors) -decreased aqueous secretion due to lack of HCO3
Latanoprost, bimatoprost, tavoprost, unoprostone (prostaglandins) -increased outflow
Which of the following has the least mineralocorticoid activity?
A Predinsolone
B Hydrocortisone
C Fludroctosione
D Dexamethasone
D
A patient with Na = 108 has a seizure and you treat it with 100ml of 3% saline. If this had not been available, what would be an equivalent dose of 8.4% sodium bicarbonate?
A 50ml
B 40ml
C 45ml
D 55ml
A
Explanation
3% sodium chloride = 513mmol/L – therefore if given 100ml, patient received approximately 51mmol.
8.4% sodium bicarbonate contains 1mmol/ml of sodium – therefore 50mls is approximately equivalent.
