Seeking Solutions in Solid-State Chemistry - Pharmaceutical Technology

Latest Issue
PharmTech

Latest Issue
PharmTech Europe

Seeking Solutions in Solid-State Chemistry
Particle-engineering technologies, such as crystal design for crystallization and producting cocrystals, particle-size reduction, and amorphous solid dispersions, help to optimize delivery of a drug.


Pharmaceutical Technology
Volume 36, Issue 10, pp. 60-62


Patricia Van Arnum
The physical form of an API is important in formulation development for resolving issues in bioavailability and solubility. Particle-engineering technologies can be applied in various ways: crystal design for controlling crystallization and producing cocrystals; particle-size reduction, achieved through jet-milling, wet polishing and nanoparticle generation; and amorphous solid dispersions, produced by several approaches, such as spray-drying (including as inclusion complexes), hot-melt extrusion (HME), and spray-congealing. Pharmaceutical Technology discussed these issues with Colin Minchom, vice president, of the Particle Design Business Unit at Hovione.

Crystallization

PharmTech: Under what type of situations would crystallization be used? How does it facilitate the delivery of poorly soluble drugs?


IMAGES ETC LTD/GETTY IMAGES
Minchom: Interest in cocrystals has increased in recent years, and the recent FDA guidance on a proposed classification of cocrystals has prompted further discussion and counter proposals from the industry. The proposed US FDA classification of cocrystals as crystalline materials containing two or more molecules in the same crystal lattice is limited but can serve as a starting point for discussion.

The addition of a cocrystal former into the crystalline structure of the API changes its physical and chemical properties. It is possible, in some cases, to improve bioavailability to adequate levels while preserving the stability of a crystalline form. For APIs with low glass-transition temperatures, a cocrystal may be favoured over the amorphous form. As such, the use of a cocrystal may be an attractive platform to overcome the solubility limitations of Biopharmaceutics Classification System Class II and Class IV drugs.


Applying acoustic levitation for elucidation of amorphous material
Cocrystal formation is a favored approach for increasing apparent aqueous solubility for poorly water-soluble molecules that have no ionizable groups, and for which salt formation is not possible, or for where the physical properties of the salts formed are not desirable. Solvates and hydrates are well-accepted crystal forms. In many ways, a cocrystal can be thought of as a solvate, but one whose components are solid at room temperature. The cocrystal will form if the resulting crystal is thermodynamically more stable than the components. Resulting cocrystal properties are dependent upon many factors, including the starting properties of the API, the physical properties of the co-former and the mechanism by which the cocrystal is formed. To increase the probability of success, we [Hovione] recommend that at early-development stages to test other proven platforms, such as solid dispersions, micronized and nanosized crystals and inclusion complexes.

PharmTech: Controlling nucleation during crystallization is an important task. What are the mechanisms for controlling crystallization?

Minchom: Where milling techniques can be thought of as top-down sizing techniques, controlled crystallization is where the desired particle-size distribution is achieved from the bottom up. The objectives of a crystallization process are twofold. On the one hand, the aim is to isolate the API in the right crystal form, typically a polymorph that provides the required level of exposure and stability. On the other hand, crystallization may also be a purification stage, whereby the impurities remain mostly dissolved in the mother liquors.

The kinetics of crystallization (nucleation and crystal growth rates) are driven by the imposed supersaturation levels. The degree of supersaturation, temperature ramp, mixing, filtration and final drying process all contribute to the final particle-size distribution. Moreover, the relative importance of each factor can change at each scale.


ADVERTISEMENT

blog comments powered by Disqus
LCGC E-mail Newsletters

Subscribe: Click to learn more about the newsletter
| Weekly
| Monthly
|Monthly
| Weekly

Survey
What role should the US government play in the current Ebola outbreak?
Finance development of drugs to treat/prevent disease.
Oversee medical treatment of patients in the US.
Provide treatment for patients globally.
All of the above.
No government involvement in patient treatment or drug development.
Finance development of drugs to treat/prevent disease.
27%
Oversee medical treatment of patients in the US.
12%
Provide treatment for patients globally.
8%
All of the above.
46%
No government involvement in patient treatment or drug development.
7%
Jim Miller Outsourcing Outlook Jim MillerCMO Industry Thins Out
Cynthia Challener, PhD Ingredients Insider Cynthia ChallenerFluorination Remains Key Challenge in API Synthesis
Marilyn E. Morris Guest EditorialMarilyn E. MorrisBolstering Graduate Education and Research Programs
Jill Wechsler Regulatory Watch Jill Wechsler Biopharma Manufacturers Respond to Ebola Crisis
Sean Milmo European Regulatory WatchSean MilmoHarmonizing Marketing Approval of Generic Drugs in Europe
Seven Steps to Solving Tabletting and Tooling ProblemsStep 1: Clean
Legislators Urge Added Incentives for Ebola Drug Development
FDA Reorganization to Promote Drug Quality
FDA Readies Quality Metrics Measures
New FDA Team to Spur Modern Drug Manufacturing
Source: Pharmaceutical Technology,
Click here