Drug Utilisation Guide

Introduction & Purpose

Drug Utilisation Studies (DUS) are designed to investigate how medicines are used in real-world clinical practice. While clinical trials tell us if a drug can work in a controlled setting, DUS tells us how it is actually being used by the general population. This is crucial for understanding prescribing patterns, patient adherence, and the real-world context of medication use.

The purpose of a DUS can be broad, but it often focuses on answering questions like:

• How many people are using a specific drug?
• For what medical reasons (indications) is it being prescribed?
• What is the typical starting dose?
• How long do patients typically remain on the treatment (persistence)?
• Are there specific populations who are more likely to use the drug?

Study Design

DUS can be conducted at two different levels, and a comprehensive study often includes both:

1. Population-Level DUS: A descriptive analysis of drug use across an entire population.
2. Patient-Level DUS: A cohort study focusing on the characteristics and behaviours of individuals who initiate a specific drug.

Participants

• For Population-Level DUS: The study includes the entire source population available in the database.
• For Patient-Level DUS: The study includes a cohort of new users of a specific drug or drug class. A “washout” period (e.g., one year with no prior use) is required to ensure that the individuals are genuinely new users. The cohort can also be restricted to a subpopulation of interest (e.g., only patients with a prior diagnosis of a specific condition).

Exposures

The primary “exposure” of interest is the medication itself. The analysis can focus on a single drug, a class of drugs, or compare the usage patterns of multiple drugs.

Outcomes

The outcomes in a DUS are measures of medication usage. These can include:

• At the Population Level:
  • Incidence of Use: The rate of new users of a drug over time.
  • Prevalence of Use: The proportion of the population using a drug at a specific point in time.
• At the Patient Level:
  • Initial Dose: The dose prescribed at the start of treatment.
  • Treatment Duration: The length of time a patient remains on the drug.
  • Treatment Discontinuation & Switching: How often patients stop the drug or switch to another.
  • Patient Characteristics: A baseline characterisation of the new users.

Follow-up

• For Population-Level DUS: Follow-up is typically over calendar time to assess trends in usage.
• For Patient-Level DUS: Follow-up starts on the date of therapy initiation (the index date) and continues until the end of data availability, loss to follow-up, or a pre-defined study end date.

Analyses

The analysis is primarily descriptive.

• Population-level analyses mirror those in an epidemiology study: calculating the incidence and prevalence of use, often stratified by age, gender, and calendar year.
• Patient-level analyses involve characterising the new user cohort and summarising the key usage metrics, such as median treatment duration and the distribution of initial doses.

How to Implement This Study

Code examples and step–by-step instructions will be added here.