Posture is crucial in a clinical study as it influences physiological characteristics. These characteristics interact with critical factors determining the pharmacokinetics of drugs (dissolution, absorption, distribution, metabolism, excretion). Posture affects blood flow which may substantially affect the absorption of drugs with a high first-pass metabolism. In addition, posture also has a prominent effect on gastric emptying.

One of the clients conducted a bioequivalence study for a highly variable molecule; however, the study resulted in a poor concentration profile and did not match bioequivalence criteria. To investigate the root cause, the Sponsor has appointed Zenovel. We have initiated an investigation in order to identify possible root causes in the study. During the investigation, it was identified that one of the factors was Posture Restriction, among other factors.

As per protocol, the time duration of posture restriction was only 02 hours, and blood samples were not collected at the bedside during these first two hours. As a way forward, we suggested keeping uniform sitting posture restriction for at least 04 hours, and all blood samples, till the time of posture restriction, to be collected at the bedside.

During the repeat study, we monitored the complete compliance along with posture restrictions. The study conducted with all suggested points and thorough monitoring resulted in favourable results.

In clinical pharmacokinetics studies, precise and appropriate posture is conducive to reducing inter-subject and intra-subject variability, especially for the highly variable drug. Hence, posture restrictions should be standardized to minimize the variability of all PK study factors and improve the outcome of bioequivalence studies.

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