by Anjum Nayyar
Getting the right drug at the right time is key for almost any patient but making sure the drug is actually being absorbed properly by the body is even more important. Pharmacy professor Ping Lee and his team are looking at ways to "get that medicine down" and improve how the body absorbs several drugs that are poorly soluble.
Lee has discovered that by engineering a glass-like "carrier" material for the drug, it is possible to enhance its solubility and control the rate at which a drug is released in the body. Low availability of drugs to the body due to poor solubility has become one of the biggest challenges in drug delivery, and Lee's research could be pivotal on this front.
He said solubility is one of the key factors affecting drug absorption as it will determine how well a compound dissolves in the aqueous environment of the gastrointestinal tract. Low solubility will mean that only a smaller amount of the drug can dissolve and will be less accessible to the body, so the goal is to maximize solubility for these poorly soluble drugs.
"Many poorly soluble drugs require the patients to take multiple capsules several times a day to achieve the desired therapy. But with this methodology one can conceivably reduce the number of dosage forms a patient needs to take," Lee said. "Once you've improved the solubility and bioavailability of the drug, you don't have to put in as much drug in the dosage form to achieve the desired therapeutic effect and economically it would be more attractive as well." The patient compliance will also be improved as the number of capsules a patient needs to take will be reduced.
Through his research Lee found that molecularly dispersing the drug in a polymer can create a buffer between the drug molecules, thereby preventing it from crystallizing in the body. The large molecule or polymer acts to delay the thermodynamic transition of the drug from the amorphous or non-crystalline state. Keeping the amorphous drug in a polymer can significantly increase its apparent solubility and enhances its bioavailability. This particular hydrogel or glassy hydrophilic polymer is most desirable for this purpose, he said, because it behaves just like glass.
"The hydrogel polymers are like glass in the dry state but once they're swollen in an aqueous environment they behave like rubber and release the entrapped drug. The hydrogel polymers in the glassy state basically stabilize the entrapped amorphous drug by dramatically reducing its mobility until it is released in the body."
His research, he said, focuses not only on developing a polymer that enhances solubility but also finding one that allows control of the rate at which a drug is released in the body.
Lee said this kind of manipulation in drug delivery can be of great value to the health care system, both for the patient and the system as a whole.
"It will help bring more pharmacologically active but poorly soluble compounds onto the market and provide the opportunity to utilize drugs that would otherwise be poorly absorbed by the body due to inadequate solubility. This could be one of the most effective methods to deliver poorly soluble drugs in the future."