Working Towards Achieving True Co-crystal Solubility: An Academic Perspective
Associate Professor Nair Rodriguez-Hornedo of the University of Michigan, speaks to Helen Winsor from Pharma IQ about whether true co-crystal solubility is within reach. To listen to the podcast now go to Working Towards Achieving True Co-Crystal Solubility.
Pharma IQ: Associate Professor Nair Rodriguez-Hornedo of the University of Michigan joins Pharma IQ today. She’ll be discussing the challenge of achieving true co-crystal solubility. Thank you so much for joining us.
N Rodriguez-Hornedo: You are welcome.
Pharma IQ: One thing I’d really like to get your opinion of is what strategies are successful in making co-crystals and which strategies are you currently using in your laboratory?
N Rodriguez-Hornedo: Yes, I think in order to successfully make co-crystals, one needs to understand what are the driving forces and the methods we use. The methods I find to be most successful are solution-mediated methods, so in order to generate super-saturation what we do is we use reaction, crystallisation methods. That is, we add the co-crystal components to a solution and just by adding the components to the solution the co-crystal falls out of solution, there is no need to cool or to evaporate.
Pharma IQ: So, do you believe that true solubility of co-crystals is achievable, based on the research that you have done so far?
N Rodriguez-Hornedo: True solubility is achievable, but we need to enable co-crystals. Cocrystals can often have much higher solubility than the parent API or the parent drug therefore they’re going to need some other component in the formulation in order to enhance that solubility or achieve the true solubility. Often for enhanced availability you may not need to achieve the true solubility. Just enhance the solubility by the number of pints you need, not necessarily to achieve the true solubility, but co-crystals are going to need enabling by careful formulation approaches.
Pharma IQ: What are the most appropriate circumstances in which would employ cocrystallisation?
N Rodriguez-Hornedo: Two come to mind. One is to modulate solubility - and most often to enhance solubility above the solubility of the parent drug. And the other one is to modulate the solubility of the parent compound in terms of the pH dependence. So, you can design cocrystals to achieve the desired pH dependence solubility. So the circumstances are twofold.
One is to enhance solubility, the other one is to modulate it, as you wish, with the desired coformer drug combination so that you achieve the desired pH solubility profile.
Pharma IQ: In your opinion, what is the optimal way to scale up co-crystal production?
N Rodriguez-Hornedo: That is related to the first question you asked me - which is what strategies we use to make co-crystals. It’s essentially an optimal way to scale up co-crystal production. It should rely on super-saturation and so controlling super-saturation by pH exchanges, by reaction crystallisation, adding components – it’s optimal in my view. It really would give you the desired control over the purity of the product.
Pharma IQ: And finally, just to round off, I understand that you’ll be presenting at the upcoming conference, Pharmaceutical Co-crystals 2010, which is going to take place from 27th - 29th September in Amsterdam. Now, for anyone interested in attending the event, what would you say would be the key learning point to be gained from your presentation?
N Rodriguez-Hornedo: Well, in my presentation I hope that people will learn and I hope to teach about the importance of the solution chemistry in regulating, in controlling, the dissolution and solubility of co-crystals. So we’re going to be talking about surfactant, about pH and what co-crystals allow you - because the two components are released, dependent on each other, they are not independent and therefore you have a whole range of possibilities. If you understand solution chemistry, you can even predict the bio-relevance advantage of co-crystals. So I hope that people will learn about how important solution chemistry is and how to, really, achieve the desired solubility of the co-crystal.
Pharma IQ: We look forward to your presentation at the event. Thank you very much for your time today, we’ll have to end it there.
N Rodriguez-Hornedo: Thank you.
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