What Is a Depot Injection?

A depot injection is an injection that delivers a medication or pharmaceutical substance into the body over a sustained period of time. The benefits of this delivery system include eliminating the need to take the drug on a daily basis and the ability to regulate the concentrations of substances in the blood. One of the drawbacks of depot injection is that the medication, once injected into the site, is not reversible. The injection is typically administered subcutaneously or intramuscularly. Subcutaneous refers to shots given into the fatty tissue just below the skin, while intramuscular shots are injected directly into the muscle.

A variety of drugs can be delivered by this method. Some of the reasons for depot injection include delivery of contraceptives, antipsychotics, prostate cancer medication, and tranquilizers. Patients suffering from conditions like schizophrenia are more likely to comply with a drug regimen when the medication is delivered via depot injection. By delivering the drugs in a slow-release manner, the patient suffering from acute psychosis is less likely to experience side effects that could be experienced with drugs that are taken orally. The psychosis is also less likely to relapse because of patient non-compliance.

A subcutaneous injection is usually administered by pinching up the skin and jabbing the needle down to the fatty tissue level, between the skin and the muscle. The reason that depot injections are given in this fashion is that there tends to be very little blood flow that reaches the fatty tissue and the medication is able to be released into the body over a long period of time. Medications such as epinephrine, insulin, and growth hormones can be injected this way. Some of the sites for these types of injections include the arms, legs, stomach, buttocks and lower back areas. The depot injection is usually given at a 90 degree or 45 degree angle into the pinched skin.

The majority of depot injections include biodegradable polymer-excipients which serve to manage the medication’s rate of release into the body. Polymer-excipients are inert substances that dilute the drug. Substances delivered by this method can often last for weeks and months, with certain formulas lasting considerably longer. People suffering from prostate cancer are typically given depot injections as a way of receiving hormone therapy and treatments. Depot injections are usually oil or solid based and can sometimes create a localized area of pain and swelling which can last for a few days.