PSA High Risk Medicines: Essential Drugs, Antidotes and Examination Tips | PharmaScholar

PSA High Risk Medicines Guide | Antidotes, Monitoring & Exam Tips

Master PSA high risk medicines with this practical guide covering anticoagulants, insulin, opioids, methotrexate, antidotes, monitoring requirements and common Prescribing Safety Assessment pitfalls.

PSA High Risk Medicines: Essential Drugs, Antidotes and Examination Tips

High-risk medicines are among the most frequently tested topics in the Prescribing Safety Assessment (PSA). These drugs are associated with a greater risk of significant patient harm if prescribed, administered or monitored incorrectly.

Understanding why drugs are high risk, how to prescribe them safely, which monitoring is required and what antidotes are available can improve both your PSA performance and future clinical practice.

At Pharmascholar, many students struggle with PSA questions because they focus on memorising drug names rather than understanding common prescribing dangers. This guide focuses on the medicines that repeatedly appear in clinical practice and PSA-style assessments.

What Are High Risk Medicines?

High-risk medicines are drugs that can cause serious harm if used incorrectly. Common reasons include:

Narrow therapeutic range
Significant overdose toxicity
Serious drug interactions
Requirement for close monitoring
Complex prescribing regimens
Frequent prescribing errors

For PSA candidates, the key is not merely knowing the drug but understanding:

✅ Common errors

✅ Monitoring requirements

✅ Drug interactions

✅ Contraindications

✅ Antidotes

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1. Anticoagulants

Warfarin

Why Is It High Risk?

Small dose changes can significantly alter anticoagulation, increasing the risk of bleeding or thrombosis.

Common PSA Pitfalls

Prescribing without checking INR
Missing interacting medicines
Failure to adjust doses
Continuing therapy before surgery

Important Interactions

Macrolides
Metronidazole
Fluconazole
Amiodarone

Antidote

Phytomenadione (Vitamin K)

Severe bleeding may also require:

Prothrombin complex concentrate (PCC)

PSA Tip

If you see a patient with a very high INR and bleeding, think:

STOP WARFARIN → GIVE VITAMIN K → CONSIDER PCC

Direct Oral Anticoagulants (DOACs)

Examples:

Apixaban
Rivaroxaban
Edoxaban
Dabigatran

Common PSA Pitfalls

Wrong renal dose
Failure to account for kidney impairment
Duplicate anticoagulation

Antidotes

Dabigatran

Idarucizumab

Factor Xa inhibitors

Andexanet alfa (specialist use)

2. Insulin

Insulin is consistently recognised as one of the highest-risk medicines used in healthcare.

Why Is It High Risk?

Prescribing errors can rapidly cause:

Severe hypoglycaemia
Seizures
Coma
Death

Common PSA Pitfalls

Incorrect insulin product
Wrong dose
Omitting long-acting insulin
Confusing units and mL

Antidote

Hypoglycaemia

Oral glucose
IV glucose
IM glucagon

PSA Tip

If a diabetic patient becomes confused, sweaty or unconscious: Always consider hypoglycaemia first.

3. Opioids

Examples include:

Morphine
Oxycodone
Fentanyl
Diamorphine

Why Are They High Risk?

Excessive dosing can cause:

Respiratory depression
Reduced consciousness
Death

Common PSA Pitfalls

Incorrect opioid conversion
Duplicate opioid prescribing
Failure to prescribe laxatives
Failure to prescribe antiemetics

Antidote

Naloxone: Used for opioid overdose and severe respiratory depression.

4. Methotrexate

Methotrexate is one of the most infamous prescribing-error drugs.

Why Is It High Risk?

Usually prescribed:

ONCE WEEKLY

Not daily.

Daily prescribing errors have resulted in fatalities.

Common PSA Pitfalls

Selecting daily rather than weekly dosing
Missing monitoring requirements
Co-prescribing interacting medicines

Monitoring

FBC
LFTs
Renal function

Important Interaction

Trimethoprim

Rescue Treatment

Folinic acid (calcium folinate)

PSA Tip

Whenever you see methotrexate: Check the frequency carefully.

5. Digoxin

Why Is It High Risk?

Digoxin has a narrow therapeutic index. Small changes in levels can increase toxicity.

Signs of Toxicity

Nausea
Vomiting
Bradycardia
Visual disturbances
Confusion

Common PSA Pitfalls

Failure to adjust in renal impairment
Prescribing despite low potassium
Missing interacting medicines

Antidote

Digoxin-specific antibody fragments (Digoxin Immune Fab)

6. Potassium

A particular issue is intravenous potassium chloride

Why Is It High Risk?

Too much potassium may cause:

Cardiac arrhythmias
Cardiac arrest

Common PSA Pitfalls

Prescribing incorrect concentration
Overly rapid replacement
Failure to monitor potassium levels

Monitoring

U&Es
ECG where appropriate

7. Heparin

Examples:

Unfractionated heparin
Low molecular weight heparin (enoxaparin)

Common PSA Pitfalls

Weight-based dosing errors
Renal impairment adjustments
Incorrect VTE prophylaxis doses

Antidote

Protamine sulfate

Quick PSA Memory Aid

Think:

WIDOHMP

Warfarin

Insulin

Digoxin

Opioids

Heparin

Methotrexate

Potassium

If a PSA question contains one of these medicines, immediately consider:

Monitoring
Dose adjustment
Contraindications
Drug interactions
Antidotes

How PharmaScholar Helps Students Master High Risk Medicines

Many students lose marks in the PSA because they focus on memorising answers rather than recognising prescribing patterns. Our one-to-one PSA tutoring sessions focus on:

High-yield PSA medicines
Prescribing safety strategies
Common examination traps
Time-saving approaches
Clinical reasoning techniques

Students often report increased confidence, reduced stress and improved accuracy when approaching prescribing questions.

Need Help Passing the PSA?

Whether you're struggling with prescribing, calculations, drug monitoring or medication safety, personalised PSA tuition can help you approach the assessment with confidence.

👉 Book a PSA tutoring session with Pharmascholar and develop the prescribing skills needed for success in both the examination and clinical practice.

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