A controlled release drug, which is also called a time release drug, is any type of pill that has been engineered to release the medication inside slowly rather than all at once. This technology has been available since the 1960s and makes it possible for patients to take certain types of medication less frequently. Most of the time, a controlled release drug is either made up of special materials that dissolve slowly in the patient's body or contains membranes that allow the drug to escape from the pill slowly. These types of pills are especially useful when a patient would benefit from maintaining a consistent amount of medication in the bloodstream.
Pills are designed to be either instant release drug or controlled release. In an instant release drug, the casing of the pill is dissolved and all the medication inside is allowed to immediately enter the patient's bloodstream. A controlled release drug, on the other hand, is engineered to allow only a small amount of medication to leave the pill and enter the bloodstream at one time.
There are a number of different instances in which a controlled release drug is an appropriate choice for a patient. Medications that work best when they are kept at constant levels are often given in this form so that the amount of the drug in the patient's system doesn't spike when the pill is first taken and then drop off as the body uses or eliminates the drug. Using this type of medication may allow a patient to take a drug only once or twice a day rather than several times throughout the day while still maintaining a more stable amount of medicine in the system than the use of several small, instant release doses would.
One of the ways that a controlled release drug can meter out a medication is by being made of a material that dissolves slowly. If the medication is infused throughout a material that must be broken down over a long period of time, digestive enzymes must act on the pill for a while for all of the medication to be released. Alternatively, a pill may contain the medication in the center and also have a semi-permeable membrane that allows the medication to leave the pill slowly. These pills are not digestible at all and, once the medication has been released, are passed through the digestive system intact. Many controlled release drugs must be taken whole so that they work properly and do not release too much medication at once.