There are two significant study designs by which drugs are evaluated in normal pharmacokinetic assays, which are known as parallel study and crossover study. Such studies are pivotal in the overall process of drug development in that they provide primary evidence of safety and efficacy. Creative Biolabs has established high-quality and efficient PK assay procedures to provide parallel/crossover study services, which our team is well-versed in performing under our own scheduling control, for a wide range of needs.

Parallel Study

A parallel study is also referred to as “between patient” or “non-crossover” study. It is defined as a type of clinical study, in which two separate treatment arms, A and B, are given so that one group receives only treatment arm A while another group receives only treatment arm B. The two treatment groups of a parallel study can either be composed of two completely separate treatments (i.e. different drugs), or simply different doses of the same drug. A major characteristic of a parallel study is randomization, which ensures accuracy of the results and lower risk of being biased. Generally, a placebo or active control are used as control groups in parallel studies.

trial design of parallel study. Fig.1 Trial design of parallel study.

Crossover Study

A crossover study, also known as a crossover trial, is a longitudinal study where subjects receive an array of different treatments or exposures. In a crossover study, all subjects should receive the same number of treatments and should be involved in the same number of periods, which is the so-called “balance” required in practically all crossover designs. Unlike the parallel study, at first one treatment group of a crossover study receives treatment A and subsequently followed by treatment arm B while the other group receives treatment B followed by treatment arm A. Actually, in most of the crossover studies, each subject receives all treatments. Many important crossover studies are controlled experiments, although it can be observational studies. Crossover studies are common in many scientific disciplines, including medicine.

trial design of crossover study. Fig.2 Trial design of crossover study.

Advantages of Parallel and Crossover Study

There are certain characteristics that allow for differentiation between parallel and crossover studies. The advantage of a parallel design is that it provides the best way to assess the effect of a drug on survival, if that is the critical endpoint in its evaluation. For instance, if there are any concerns about carryover effects, a parallel study is considered more appropriate. Similarly, if the disease being studied has a possible chance of progression during the time in which the study occurs, parallel study might also be more beneficial. However, crossover study has two advantages over parallel study. First, the influence of confounding covariates is decreased because each crossover subject serves as its own control. Second, optimal crossover studies are statistically efficient and thus require fewer subjects than do non-crossover designs.

Creative Biolabs, a premier preclinical CRO in the industry of drug discovery, is committed to providing expert high-quality contract research services to our clients all over the world. With extensive experience and excellence professional skills, our scientists have a solid track record in in vivo PK assay and drug development capabilities. We offer pharmacokinetic, especially parallel/crossover studies in several animal species, such as rodents, rabbits and non-human primates. A wide range of routes of administration are available for a wide variety of test articles, which includes small molecules, large molecule, vaccines, antibodies, proteins, and etc. Our veteran scientists are proud to assist you to select the most appropriate study design for your research project, according to your specific needs.

In addition to parallel/crossover study services, Creative Biolabs also offers other in vivo pharmacokinetic assay services. Following is the list of available services of pharmacokinetics assays at Creative Biolabs, which highlight the experience and capabilities of our method development and validation services:

Besides, you might be also interested in other in vivo PK studies listed below:

If you have any special needs in in vivo pharmacokinetic assays or be interested in learning more about Creative Biolabs’ pharmacokinetic assay services, please contact us for more information.

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