Pharmaceutical companies are responding to the high cost of introducing new drugs to market in different ways. For new drugs,
companies are examining drug products and their delivery systems far earlier in the design phase than they have in the past
to ensure success of the new drug and device combination. At the same time, existing APIs are being repurposed for new therapeutic
treatments or delivered using improved formulation and delivery methods that may better resolve the physiological, biochemical,
and physicochemical barriers. These shifts have increased the industry's focus on the drug-delivery platform as an enabling
technology that can optimize drug efficacy and cost-effectiveness.
Simulation software is one technology that can improve device performance by allowing pharmaceutical companies to virtually
model and prototype the delivery of new drugs. Various properties can be examined, including the drug's composition, particle
size, flow, andhuman physiology.
Numerical simulation tools, such as finite element analysis (FEA) and computational fluid dynamics (CFD) provide a way to
rapidly and economically examine a wide array of drug-delivery technologies. Early in the design cycle, numerical simulation
identifies designs and operational conditions that might not meet therapeutic requirements, thereby allowing companies to
address these and to develop accurate, safe, and effective design before the first prototype is developed. Later on, models
can be constructed to simulate the actual drug-delivery process to humans. Although these advanced studies entail more upfront
effort, especially if validation is required, they provide significant advantages over experimentally driven develoment processes.
Therefore, they can decrease the chance of design changes after the product enters animal or clinical trials. This article
describes these simulation technologies and related case studies.
Computation fluid dynamics tools
Because of the fluidic nature of drug delivery, CFD tools are commonly used to understand and optimize the delivery process.
CFD takes advantage of numerical methods to solve the fundamental equations for fluid flow and heat/mass transfer. The process
begins by creating the medical device in a computer aided design (CAD) tool or in other solid modeling software. The next
step is to decompose the domain into a computation grid or mesh. Anatomic structures are incorporated as needed using one
of two approaches:
- Creating an idealized anatomic model (using solid modeling software); or
- Extracting the anatomic structure from medical-scan images using segmentation software, such as Mimics (Materialise) or ScanIP
(Simpleware).
Segmentation tools combine the anatomic data with the device, create a mesh, and export the meshed assembly in a format readable
by most leading commercial simulation software. The user enters material property data, initial and boundary conditions, and
submits the job to the CFD solver. Once the problem is converged, the user visually and quantitatively reports results for
fluid flow, density, drug concentration, and other variables. Cut planes and surface plots are the most common way of displaying
the results. Alternatively, one can extract point, surface, or volumetric results for quantitative comparisons to experimental
or other data.
