Mixed Deck — All PSA Topics Flashcards
100 cards from real PSA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 20 Mixed Deck — All PSA Topics flashcards as text
NSAIDs cause acute kidney injury in patients with renal impairment primarily through which mechanism?
Answer: Inhibition of prostaglandin-mediated afferent arteriolar dilation
NSAIDs inhibit prostaglandins that maintain afferent arteriolar dilation in states of low renal perfusion, reducing GFR and precipitating acute kidney injury.
What is a drug's half-life?
Answer: The time required for the drug's plasma concentration to decrease by 50%
Half-life determines dosing frequency: drugs with short half-lives need more frequent dosing, while long half-life drugs can be given less often.
Amiodarone inhibits CYP2C9. A patient stabilised on warfarin starts amiodarone. What monitoring and action is required?
Answer: Reduce warfarin dose and increase INR monitoring frequency
Amiodarone's CYP2C9 inhibition increases warfarin plasma levels, raising bleeding risk; warfarin dose reduction and close INR monitoring are required.
What is bioavailability?
Answer: The fraction of an administered drug dose that reaches systemic circulation in active form
Bioavailability measures what proportion of the administered drug reaches the bloodstream in active form. IV drugs have 100% bioavailability; oral drugs vary.
In severe hepatic impairment (Child-Pugh C), which drugs require the greatest dosing caution?
Answer: Drugs with a high hepatic extraction ratio
High hepatic extraction ratio drugs (e.g., morphine, propranolol) rely heavily on liver blood flow and enzyme activity; hepatic impairment severely reduces their first-pass and systemic clearance.
A 72-year-old post-CABG patient on isosorbide mononitrate presents to ED with severe hypotension. The nurse notes he recently took a medication for erectile dysfunction. Which interaction explains this?
Answer: Sildenafil and isosorbide mononitrate causing synergistic cGMP-mediated vasodilation and profound hypotension
PDE5 inhibitors like sildenafil are absolutely contraindicated with nitrates as both increase cGMP, causing profound additive vasodilation and potentially fatal hypotension.
Which of the following drugs does NOT typically require dose reduction in renal impairment?
Answer: Rifampicin
Rifampicin is primarily hepatically metabolized and excreted in bile, so it does not require dose reduction in renal impairment.
A renally impaired patient on digoxin starts verapamil for rate control. The digoxin level rises to a toxic concentration. What is the primary mechanism?
Answer: Verapamil inhibits P-glycoprotein-mediated renal and biliary excretion of digoxin, reducing its elimination
Verapamil inhibits P-glycoprotein in the renal tubule and biliary epithelium, the primary secretory pathways for digoxin; renal impairment compounds this by independently reducing filtration-based elimination.
A patient requires eradication therapy for Helicobacter pylori. Which regimen is recommended as first-line in areas with clarithromycin resistance >15%?
Answer: Bismuth quadruple therapy (PPI + bismuth + tetracycline + metronidazole)
Bismuth quadruple therapy is preferred in regions with high clarithromycin resistance, as it avoids clarithromycin and achieves superior eradication rates.
Why do elderly patients require special prescribing considerations?
Answer: Altered pharmacokinetics (reduced kidney/liver function, body composition changes) and increased sensitivity to many drugs
Aging reduces kidney and liver function, changes body fat distribution, and increases drug sensitivity, requiring lower doses and careful monitoring.
A hospitalized patient develops Clostridioides difficile colitis classified as non-severe. What is the first-line treatment?
Answer: Oral vancomycin 125 mg four times daily
Current IDSA guidelines recommend oral vancomycin (or fidaxomicin) over metronidazole as first-line therapy for non-severe C. difficile infection due to superior outcomes.
A patient on dabigatran presents with life-threatening gastrointestinal bleeding. Which specific reversal agent should be used?
Answer: Idarucizumab (Praxbind)
Idarucizumab is a monoclonal antibody fragment specifically designed to reverse dabigatran; andexanet alfa reverses factor Xa inhibitors such as rivaroxaban and apixaban.
An adult weighing 48 kg is prescribed paracetamol for post-operative pain. What is the maximum safe single dose?
Answer: 720 mg
For patients weighing less than 50 kg, the maximum single dose of paracetamol is 15 mg/kg, giving 720 mg for a 48 kg adult.
A patient grows an ESBL-producing Klebsiella pneumoniae from a blood culture. Which antibiotic is the most appropriate definitive therapy?
Answer: Meropenem
Carbapenems such as meropenem are the treatment of choice for serious ESBL-producing Enterobacterales infections; beta-lactam/beta-lactamase inhibitors and cephalosporins are unreliable.
A 68-year-old male is prescribed levofloxacin for pneumonia. Which adverse effect should prompt immediate discontinuation and closest monitoring?
Answer: Tendon pain, especially at the Achilles
Fluoroquinolones carry an FDA black box warning for tendinopathy and tendon rupture, particularly the Achilles tendon, and must be stopped immediately if tendon pain occurs.
Which prescriber type is legally authorized to prescribe Schedule II controlled substances in the US, assuming state law permits it?
Answer: Physician assistants (PA) with a valid DEA registration
Physician assistants with a valid state prescriptive authority and DEA registration can prescribe Schedule II controlled substances in states that grant them that authority.
Which pharmacokinetic/pharmacodynamic parameter best predicts the efficacy of vancomycin against MRSA?
Answer: AUC/MIC ratio
Current guidelines recommend targeting an AUC/MIC ratio of 400–600 for vancomycin, as this best correlates with clinical outcomes and minimizes nephrotoxicity.
A 78-year-old woman with hypertension, AF, and type 2 diabetes on amlodipine, apixaban, and metformin develops gout. She is prescribed indometacin. What is the primary prescribing concern?
Answer: NSAIDs combined with anticoagulants increase bleeding risk and can worsen renal function and blood pressure
NSAIDs combined with anticoagulants significantly increase gastrointestinal bleeding risk; they also worsen hypertension and can precipitate acute kidney injury through prostaglandin inhibition.
Which prescription abbreviation is considered most dangerous and should always be written in full to prevent a medication error?
Answer: 'U' for units, which can be misread as a zero causing a tenfold overdose
Writing 'U' for units is dangerous because it can be misread as '0', turning '10U of insulin' into '100 units' — a potentially fatal tenfold overdose.
The abbreviation 'U' for units is on the Institute for Safe Medication Practices (ISMP) 'Do Not Use' list. What dangerous misinterpretation can occur?
Answer: 'U' can be misread as '0,' turning '10 U' into '100'
The abbreviation 'U' for units can be misread as the number '0,' so '10 U' of insulin could be dispensed as 100 units, a tenfold overdose.