Comparative efficiencies of randomized concentration- and dose-controlled clinical trials

Area of Science:

• Pharmacometrics
• Clinical Trial Design
• Pharmacodynamics

Background:

• Previous research suggested randomized dose-controlled trials (RDCT) are less efficient than randomized concentration-controlled trials (RCCT).
• This conclusion was based on a specific linear pharmacodynamic model with limited concentration-response range.

Purpose of the Study:

• To compare the estimation efficiencies of RDCT and RCCT across various pharmacodynamic models.
• To determine if the bias and inefficiency of RDCT, as previously reported, apply to broader models.

Main Methods:

• Simulations were conducted using different pharmacodynamic models (restricted linear, unrestricted linear, log-linear).
• Pharmacokinetic and pharmacodynamic variability were systematically introduced.
• Efficiency ratios of RCCT to RDCT were calculated for parameter estimation.

Main Results:

• RCCT showed higher efficiency than RDCT for the restricted linear model (3.1x).
• Efficiency gains for RCCT were less pronounced for unrestricted linear (1.5x) and log-linear (1.2x) models.
• Pharmacodynamic variability significantly reduced the efficiency advantage of RCCT over RDCT.

Conclusions:

• RCCT generally offers minimal to moderate efficiency improvements over RDCT for estimating concentration-effect parameters.
• The statistical advantages of RCCT are often not substantial enough to warrant its use.
• RCCT may be considered for drugs with narrow therapeutic indexes or specific response profiles.