40 Drug Interactions Every Pharmacy Technician Should Know.

What drug interactions get tested on the PTCB exam?

On the PTCB exam, drug interactions are tested with a focus on high-risk, commonly prescribed drugs and clinically significant outcomes, rather than complex pharmacokinetic details. Drug interactions are typically limited to the top 200 medicines, but are usually confined to a smaller number of drugs.

Pharmacy technicians are expected to recognize interactions that can lead to serious safety concerns, such as bleeding, arrhythmias, CNS depression, or toxicity. Commonly tested examples include drug interactions that involve:

• Anticoagulant or antiplatelet drugs
• Cardiovascular drugs
• CNS drugs
• Antibacterial drugs

For instance, combinations that increase bleeding risk, additive sedation or CNS effects (e.g. opioids with benzodiazepines), or electrolyte imbalances (such as hyperkalemia etc.) are frequently assessed. Drug interactions involving CYP enzyme inhibition or induction (affecting drug levels) may also appear, but typically in a simplified, recognition-based format.

The exam may present drug interactions through prescription scenarios, asking the pharmacy technician to identify combinations that should be flagged for pharmacist review.

For your study preparation, there are four key criteria to keep in mind:

• Patient safety
• Recognizing common and well-known interactions
• Recognizing red flags or contraindications
• Understanding the basic clinical consequences of the drug interaction

Overall, success on this topic comes from being able to quickly identify common, clinically relevant interaction pairs and their associated risks. Try to keep your study focus within this narrower parameter to avoid studying more drug interactions than is required or necessary.

PTCB Exam Drug Interactions: The Top 40.

Below, we highlight 40 key drug interactions that pharmacy technicians should be familiar with.

The goal is not to memorize every detail, but to recognize the key types of interactions commonly tested. In-depth mechanisms are not required; any additional detail provided is given to support your understanding of how these interactions occur.

As emphasized earlier, the purpose of testing drug interactions on the PTCB exam is to ensure you can recognize common and clinically significant interactions at a foundational level. Too many technicians make the common mistake of studying more interactions than is required, or to a level of depth that is not tested. This makes the topic more difficult than it needs to be.

Keep this recommendation in mind as you study the table below.

PTCB Exam Sample Questions.

As we learned, pharmacy technicians should only learn the most significant drug interactions. Avoid the temptation to learn too many interactions. It not only makes your study more difficult and less focused, but that level of detail will not get tested anyway.

Instead, keep your study focused on major interactions that affect the top 200 drugs. To help you with this goal, we put together five sample PTCB questions on drug interactions (below). These questions reflect the style, standard, and wording of interaction questions tested on the PTCB test – and test the information we put together in the table above.

Take a moment to attempt these questions first before learning more about each correct answer in the section directly below.

Question 1.

Which of these drug classes opposes the therapeutic effects of drugs such as albuterol and salmeterol?

a. ACE inhibitors

b. corticosteroids

c. NSAIDs

d. beta-blockers

Question 2.

PDE5 inhibitors are contraindicated with which other drug class?

a. benzodiazepines

b. nitrates

c. antipsychotic drugs

d. 5-alpha reductase inhibitors

Question 3.

Which drug class significantly increase levels of lithium, a drug used in the management of bipolar disorder?

a. loop diuretics

b. antiplatelet drugs

c. 5-HT3 receptor antagonists

d. all of the above

Question 4.

Taken together, opioids and benzodiazepines increase the risk of which adverse effect?

a. hypertension

b. hepatotoxicity

c. respiratory depression

d. thrombocytopenia

Question 5.

Due to reduced absorption, antacids should be avoided with which drug class?

a. bisphosphonates

b. NSAIDs

c. oral contraceptive drugs

d. immunosuppressant agents

Answer Explanations.

Answer to Question 1 – d. Beta-blockers

Albuterol and salmeterol are beta-2 agonists, drugs that work by opening airways to help alleviate respiratory symptoms of patients with asthma and COPD.

Beta-blockers, by their very nature, oppose the effects of beta agonists.

Answer to Question 2 – b. Nitrates

Nitrates can cause low blood pressure (hypotension). So can PDE5 inhibitors, such as sildenafil and tadalafil – drugs used to manage erectile dysfunction.

Taking both drugs at the same time must be avoided because it can cause severe hypotension.

Answer to Question 3 – d. Loop diuretics

Loop diuretics include drugs such as furosemide and bumetanide.

They reduce the rate at which lithium is eliminated from the body. This increases lithium levels and therefore increases the risk of adverse effects.

Answer to Question 4 – c. Respiratory depression

Both benzodiazepines and opioids can slow breathing.

In severe cases, this can cause respiratory depression – and this risk is amplified if both drugs are taken together.

Answer to Question 5 – a. Bisphosphonates

Bisphosphonates are drugs used to treat bone disorders such as osteoporosis. Examples include alendronate and zoledronic acid.

Antacids bind to and reduce the absorption of bisphosphonates in the body. At least 2-hours must elapse before/after taking bisphosphonates before an antacid can be safely taken.

How to Build Drug Interactions into Your Study Plan.

To be effective, pharmacy technicians should build the following structure into their long-term study plan:

• Only learn major drug interactions that largely impact the top 200 medicines.
• Avoid little known or rare interactions. They will not be tested.
• Where possible, learn interactions by ‘drug class’ rather than by individual drugs. This narrows down how many interactions you need to learn.
• Learn interactions in groups of 5–10 per week. Revise these interactions daily; and test yourself each week. Repeat this process with the next 5-10 interactions.
• Consider the fundamental nature of the drug class. For example: if the drug affects the CNS (central nervous system; brain/spinal cord), it’s more likely to cause side effects such as sedation, slowed breathing, and dizziness. Other drugs that affect the CNS can worsen these effects etc. The same is true of alcohol.
• In MCQ questions, any reference to rare or little-known drugs is unlikely to be the correct answer. After all, only major drug interactions are tested! Always eliminate incorrect answers where possible.
• Create neat and effective study tools to recall key interactions. Use flashcards and mnemonics to hammer home those difficult-to-recall interactions.
• Always try to understand the reasons why two drugs / drug classes interact. By understanding the reasons, it makes the interaction much more memorable!

If you are a member of our online program, you already have access to our full Unit lesson on Drug Interactions and Contraindications. This details all interactions technicians need to know, how to memorize them easily and effectively – and also comes with complete high-resolution PDF notes and flashcards to supplement your study. Access those resources to build upon what you have learned today.

If you haven’t yet become a member, learn more about our online course.

Hope you found today’s review of drug interactions helpful. Check back to our PTCB blog soon for more exclusive material to help you study and prepare for your pharmacy technician exam!