PTCB Guide to Therapeutic Duplications.

Why are Therapeutic Duplications Tested?

For the PTCB exam, therapeutic duplications is a must-prepare topic for pharmacy technicians. It can be tested under the Medications knowledge domain or the Order Entry & Processing knowledge domain.

For the PTCB test, pharmacy technicians are required to learn:

• The definition of what constitutes a therapeutic duplication
• How to recognize therapeutic duplications from a patient profile
• Understanding the clinical consequences of duplications

Recognizing therapeutic duplications is core part of a pharmacy technician’s role in preventing medication errors, ensuring that prescriptions are safe and appropriate, and supporting pharmacists in clinical decision-making. While technicians do not make final clinical decisions, they must flag duplications for the pharmacist to review.

Pharmacy technicians are not required to clinically intervene, but they must recognize therapeutic duplications and report them to the pharmacist where they do occur.

What is a Therapeutic Duplication?

Key definition: a therapeutic duplication occurs when a patient is prescribed two or more medicines that have the same or similar pharmacologic effects or are used for the same therapeutic purpose.

These medicines may belong to the same drug class or different classes but produce overlapping effects. Therapeutic duplications can be intentional or accidental:

• Intentional duplications are sometimes seen in clinical practice when a physician deliberately wants to combine drugs for additive effects – for example, a clinician who prescribes two antidepressants of the same class in patients with severe depression.
• More often, duplications are unintentional and pose a risk of increased adverse effects. Therapeutic duplications have three further consequences: they increase the risk of additional medication error; increase healthcare costs for the patient, and they serve to waste resources.

In a pharmacy setting, identifying duplications is an essential part of medication safety checks. Recognizing duplications requires knowledge of drug classes, indications, and mechanisms of action. This explains why duplications can be tested as part of the Medications knowledge domain, but also the Order Entry & Processing knowledge domain. In other words, duplications impact the science of medicines as well as the safe practice of pharmacy for patients.

Key characteristics of therapeutic duplications include:

• Drugs from the same pharmacologic class (e.g. two beta-blockers)
• Drugs with similar therapeutic effects (e.g. two antihypertensives from different classes)
• Drugs prescribed for the same clinical indication

A duplication does not always imply a prescription error, but unnecessary duplication increases the risk of side effects, toxicity, and patient confusion. In the case above, a patient may be taking two antihypertensive drugs for the treatment of hypertension where they may only require one. Combining two antihypertensive drugs increases the risk of adverse effects.

Are Therapeutic Duplications the same as Polypharmacy?

No.

Therapeutic duplications and polypharmacy are not the same, though they can overlap. As we learned, therapeutic duplication occurs when a patient takes two or more drugs with the same or similar therapeutic effects, such as two ACE inhibitors or two NSAIDs, which can increase the risk of adverse effects.

Key Definition: polypharmacy refers to the use of multiple medicines simultaneously (previously defined as “five or more” medicines) regardless of therapeutic overlap, often seen in elderly or chronically ill patients.

Today, it is recognized that some older patients must take multiple medicines concurrently and so the categorization is between “appropriate polypharmacy” and “inappropriate polypharmacy”. While polypharmacy may include therapeutic duplications, a patient can have polypharmacy without any duplication, and a duplication can occur even with just two medicines.

Key Examples of Therapeutic Duplications.

Let’s take a look at some more examples of therapeutic duplications:

• NSAIDs: prescribing ibuprofen and naproxen together for pain relief is a duplication because both reduce inflammation and pain through the same mechanism.
• Antihypertensives: using lisinopril and enalapril simultaneously represents a duplication (both are ACE inhibitors). Even combining drugs from different classes, such as lisinopril and losartan, may require clinical justification since both drugs affect the same system (in this case, the renin-angiotensin system).
• Statins: prescribing atorvastatin and simvastatin together is unnecessary and potentially dangerous, as both lower LDL cholesterol in the same way.
• Benzodiazepines: using lorazepam and diazepam concurrently for anxiety without a specific clinical reason is a duplication.
• Antidepressants: combining two SSRIs (e.g. sertraline and fluoxetine) can increase the risk of serotonin syndrome and is considered a therapeutic duplication.
• Other common scenarios: two inhaled bronchodilators of the same class; two opioid analgesics prescribed together (increasing the risk of respiratory depression); or duplicate antidiabetic agents that have overlapping mechanisms (increasing the risk of hypoglycemia).

On your PTCB exam, you may be asked scenario-based questions (see below for examples!).

For instance, given a list of the medicines a patient is taking you are asked to identify a potential duplication from those medicines.

PTCB Exam-Style Questions.

Below you can find three sample PTCB exam questions on the topic of therapeutic duplications.

These three questions reflect the type of questions that get tested about duplications on the exam – both the style and difficulty. As always, have a go at the questions yourself before comparing your answers with the explanations (in the section below).

Question 1.

All these combinations are examples of therapeutic duplications, except?

a. atorvastatin and simvastatin

b. lorazepam and diazepam

c. lisinopril and amlodipine

d. naproxen and diclofenac

Question 2.

A patient with treatment-resistant depression presents to the pharmacy. They are taking:

• Sertraline 50 mg daily
• Fluoxetine 20 mg daily
• Bupropion 150 mg daily

Based on this patient information, what conclusion can be drawn?

a. sertraline and fluoxetine constitute a therapeutic duplication

b. sertraline and bupropion constitute a therapeutic duplication

c. all three drugs represent a therapeutic duplication

d. no therapeutic duplication is present

Question 3.

A patient’s medication profile includes:

• Prilosec 20 mg daily
• Nexium 20 mg daily
• Famotidine 20 mg twice daily

As the pharmacy technician reviewing this patient’s profile, which statement is correct?

a. There is a therapeutic duplication between Prilosec and Famotidine

b. There is a therapeutic duplication between Prilosec and Nexium

c. There is a therapeutic duplication between Nexium and Famotidine

d. No therapeutic duplication is present

Answer Explanations.

Answer to Question 1 – c. Lisinopril and amlodipine

Lisinopril is an ACE inhibitor, and amlodipine is a calcium channel blocker. Both drugs are from different classes with no overlapping mechanism and so this does not constitute a therapeutic duplication.

Answer to Question 2 – a. Sertraline and fluoxetine constitute a therapeutic duplication

Both sertraline and fluoxetine are SSRI drugs.

We’re told that the patient is taking bupropion, which is also an antidepressant. But we are informed that the patient has “treatment-resistant depression” and so, in these cases, it’s not uncommon for a second antidepressant from a different class to be used to help control the patient’s symptoms.

Answer to Question 3 – b. There is a therapeutic duplication between Prilosec and Nexium

Prilosec (omeprazole) and Nexium (esomeprazole) are both proton pump inhibitors (PPIs) with overlapping acid-suppressing effects. Famotidine is an H2 receptor antagonist, which works differently, so it is not considered a duplication with either PPI.

PTCB Cheat Sheet.

Over the course of today’s guide, you learned:

• Definition of therapeutic duplications: when two or more drugs are taken with overlapping effects or therapeutic functions.
• Primary role for technicians: to identify duplications, to flag for pharmacist review, to prevent adverse effects.
• Consequences: therapeutic duplications increase the risk of serious adverse effects. These effects may then need to be treated with more medicines, and so an avoidable cycle is created.
• Polypharmacy: the concurrent use of multiple medicines by a single patient. Therapeutic duplications may or may not be present.
• Common drug classes associated with duplications:
  • NSAIDs: ibuprofen, naproxen
  • ACE inhibitors: lisinopril, enalapril, perindopril
  • Statins: atorvastatin, simvastatin, lovastatin
  • Benzodiazepines: lorazepam, diazepam, midazolam
  • SSRIs: sertraline, fluoxetine, escitalopram, paroxetine
• Remember: focus on same-class drugs and overlapping indications and/or mechanism
• Action: verify patient history, check for duplications during order entry, alert pharmacist, and document concerns.

Hope you found this week’s PTCB guide to therapeutic duplications useful!

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