Usually when you eat or drink something, it's digested and absorbed straight away. In the past this was also true for medication. However, a lot of drugs these days are treated or packaged in a way that means the drug is released slowly into the blood stream. This means that you don't have to take the drug as frequently as before. Some of the drugs that work like this include hayfever treatment, pain medication, and anti-depressants. The method is called sustained release.
The simplest way of making a drug sustained-release is by packaging it in some kind of polymer (figure 1). Each grain of medication is coated in a material that dissolves slowly. The granules can be compressed into a tablet, or packed into a capsule. The thickness and type of material determine how slow the drug release will be.
Another way is to mix the drug with an insoluble material (figure 2). The drug gets released as it slowly diffuses out of the insoluble material.
A third method mixes the previous two techniques: the drug is packaged in a material that is partially soluble (figure 3). Parts of the membrane around the drug dissolves, and the drug diffuses out of the coating in this way.
Recently an additional material has been developed, called hydrogel (figure 4). A drug can be packaged in a hydrogel, which will safely transport the drug through the stomach without dissolving. Then, when the hydrogel is in a specific environment (for example, a specific pH), it swells up and the drug can diffuse through pores formed in the coating.
It is important to remember to follow the instructions for taking a specific drug. For example, if you chewed a tablet that was designed to be slow release using technique number 1, as described here, you would destroy its slow-release ability.
The contraceptive implant, Implanon, contains the hormone progestogen. This hormone is released slowly over 3 years. It is imbedded in a polymer called evatane, and the release of the hormone is further controlled by a membrane that ensures a consistent daily dose.
The simplest way of making a drug sustained-release is by packaging it in some kind of polymer (figure 1). Each grain of medication is coated in a material that dissolves slowly. The granules can be compressed into a tablet, or packed into a capsule. The thickness and type of material determine how slow the drug release will be.
Another way is to mix the drug with an insoluble material (figure 2). The drug gets released as it slowly diffuses out of the insoluble material.
A third method mixes the previous two techniques: the drug is packaged in a material that is partially soluble (figure 3). Parts of the membrane around the drug dissolves, and the drug diffuses out of the coating in this way.
Recently an additional material has been developed, called hydrogel (figure 4). A drug can be packaged in a hydrogel, which will safely transport the drug through the stomach without dissolving. Then, when the hydrogel is in a specific environment (for example, a specific pH), it swells up and the drug can diffuse through pores formed in the coating.
It is important to remember to follow the instructions for taking a specific drug. For example, if you chewed a tablet that was designed to be slow release using technique number 1, as described here, you would destroy its slow-release ability.
The contraceptive implant, Implanon, contains the hormone progestogen. This hormone is released slowly over 3 years. It is imbedded in a polymer called evatane, and the release of the hormone is further controlled by a membrane that ensures a consistent daily dose.
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