Preformulation involves the characterization of a drug's physical, chemical, and mechanical properties in order to choose what other ingredients (excipients) should be used in the preparation.
[1] Formulation studies then consider such factors as particle size, polymorphism, pH, and solubility, as all of these can influence bioavailability and hence the activity of a drug.
A high drug load may pose flow problems or require large capsules if the compound has a low bulk density.
By the time phase III clinical trials are reached, the formulation of the drug should have been developed to be close to the preparation that will ultimately be used in the market.
For example, slow dissolution rates can prolong the duration of action or avoid initial high plasma levels.
Treatment of active ingredient by special ways such as spherical crystallization[2] can have some advantages for drug formulation.
A tablet is usually a compressed preparation that contains: The dissolution time can be modified for a rapid effect or for sustained release.
Special coatings can make the tablet resistant to the stomach acids such that it only disintegrates in the duodenum, jejunum and colon as a result of enzyme action or alkaline pH.
They may also contain a mixture of slow and fast release particles to produce rapid and sustained absorption in the same dose.
There are a number of methods by which tablets and capsules can be modified in order to allow for sustained release of the active compound as it moves through the digestive tract.
Another method by which sustained release is achieved is through an osmotic controlled-release oral delivery system, where the active compound is encased in a water-permeable membrane with a laser drilled hole at one end.
Many parenteral formulations are unstable at higher temperatures and require storage at refrigerated or sometimes frozen conditions.
Lyophilized drugs are stored in vials, cartridges, dual chamber syringes, and prefilled mixing systems.
Lyophilization, or freeze drying, is a process that removes water from a liquid drug creating a solid powder, or cake.