What is RTSM (formerly IWRS) in clinical research?

An Interactive Web Response System (IWRS) is the web-based software clinical research sites use to randomize patients and manage investigational drug supply across a trial. It replaced the phone-based Interactive Voice Response System (IVRS) of the 1990s, and today most sponsors call this technology RTSM, Randomization and Trial Supply Management.

Here's the part that trips people up: the industry renamed the technology. What teams once called IVRS, then IWRS, then IRT, most now call RTSM (Endpoint Clinical, n.d.). The label changed because the job grew. These systems went from recording responses to running randomization and the entire drug supply chain, and in 2025 cloud and web-based platforms made up 91.4% of the RTSM market (Grand View Research, 2025). Below is what the technology is, what it does, and why the name keeps shifting.

From IVRS to IWRS to RTSM: how the technology got its name

The technology started on the phone. In the 1990s, an Interactive Voice Response System (IVRS) let clinical research site staff randomize patients and request drug supply by pressing keypad buttons during a call. When the internet became standard, most systems moved to the web as Interactive Web Response Systems (IWRS), and staff switched from phone keypads to computer prompts. A web system connects to other trial platforms and runs from any location, which is why it took over.

When sponsors ran both voice and web versions, they coined IxRS to mean either one, and Interactive Response Technology (IRT) became the umbrella term for all of it. RTSM is the current term (Endpoint Clinical, n.d.). It moves the focus off what the technology does, record responses, and onto the role it plays, running randomization and trial supply. In practice, today's IRT and RTSM systems do the same core work, so you'll still see “IWRS” in protocols, RFPs, and searches even though the field has moved on (Suvoda, 2026). For a full side-by-side, see Antidote's guide to IWRS vs. RTSM.

What an IWRS (now RTSM) does in a clinical trial

Whatever you call it, the system handles four jobs:

• Patient management: registering new patients and randomizing them into the correct treatment arm without bias.
• Drug supply management: tracking investigational product (IP) inventory and running complex dispensing rules. Modern systems forecast when a site will run low and trigger resupply before it does.
• Documentation and reporting: generating real-time reports so study managers see trial status without waiting on a data pull.
• Integration: connecting to the clinical trial management system (CTMS), electronic data capture (EDC), and electronic patient-reported outcome (ePRO) tools, which cuts the time teams spend reconciling data across systems.

The payoff is money and time. RTSM runs about 2-3% of the total study budget for Phase II and III trials and returns it through 15-20% less drug waste, fewer protocol deviations, and faster database lock (Suvoda, 2026). Each system is validated to 21 CFR Part 11, with the audit trails regulators expect.

The name moved from IWRS to RTSM because supply management became as make-or-break as randomization.

An RTSM keeps randomization and drug supply on track once patients reach your sites. Getting the right patients there is a separate problem, and it's the one that stalls most trials.