Drug carriers are compounds people can attach to drug molecules for targeted delivery, increased efficiency, or controlled release. Many can also act as buffers to reduce the toxic effects of medications. These include synthetic and natural compounds from a variety of sources, ranging from lipids to nanoparticles. Drug companies work on drug carrier development to provide themselves with an array of products they can use with their pharmaceuticals.
When patients take medications, they do not take a pure form of the active ingredient. Medications come with fillings and coatings to adjust the method of drug delivery. These compounds can also change the way the drug acts in the body. The drug carriers determine where the drug travels and how it behaves when it gets there.
A common example is a controlled release coating. This limits the release of the drug into the body, allowing a doctor to deliver a dose slowly over time, rather than all at once. Drug carriers can also resist stomach acid to make sure a drug will be able to reach the intestines, where the mucus membranes can absorb the medication. Other drug carriers may attach to the drug molecules to make sure they only target certain kinds of cells, like cancer cells or bacteria.
Drug carriers may contain buffers to prevent medications from damaging body tissue. Many drugs are toxic, and the toxic effects must balance with the therapeutic ones for the drug to be effective. A buffer can allow a patient to take a drug safely while making sure it still gets where it needs to go. The molecules used as drug carriers can also determine where a medication goes. Drugs that must pass the blood-brain barrier, for example, need to be on very small molecules or they will not be able to penetrate the brain tissue.
In the process of developing a drug carrier, companies look at how it acts in the body on its own before combining it with medications. One concern is the possibility of building up a store of a drug carrier because the body does not know how to eliminate it. This could potentially cause health problems for the patient over time.
Some drug carriers are proprietary. Drug companies use these in drug development to come up with novel ways of providing drug delivery to patients, and they protect them as trade secrets. Once a patent expires, any company can replicate the method and use it with its own medications. Others are freely and openly available, and anyone can use them to compound and develop new drugs.