<unk>  is commonly used for medication administration. Medication administered in the muscle is generally quickly absorbed in the bloodstream, and avoids the first pass metabolism which occurs with oral administration. The medication may not be considered 100% bioavailable as it must still be absorbed from the muscle, which occurs over time. An<unk>  is less invasive than an intravenous injection and also generally takes less time, as the site of injection (a muscle versus a vein) is much larger. Medications administered in the muscle may also be administered as depot injections, which provide slow, continuous release of medicine over a longer period of time. Certain substances, including ketamine, may be injected<unk> ly for recreational purposes. Disadvantages of<unk>  administration include skill and technique required, pain from injection, anxiety or fear (especially in children), and difficulty in self-administration which limits its use in outpatient medicine. Vaccines, especially inactivated vaccines, are commonly administered via<unk> . However, it has been estimated that for every vaccine injected<unk> ly, 20 injections are given to administer drugs or other therapy. This can include medications such as antibiotics,<unk> munoglobulin, and hormones such as testosterone and medroxyprogesterone. In a case of severe allergic reaction, or anaphylaxis, a person may use an epinephrine autoinjector to self-administer epinephrine in the muscle.
Intramuscular injection
Subcutaneous injection
Intraperitoneal injection
Subcutaneous infusion
Subcutaneous implant
Intrathecal administration
Intradermal injection
Transdermal spray