encompasses intravenous (IV), intramuscular (IM), subcutaneous (SC) and intradermal (ID) administration. Parenteral administration generally acts more rapidly than topical or enteral administration, with onset of action often occurring in 15–30 seconds for IV, 10–20 minutes for IM and 15–30 minutes for SC. They also have essentially 100% bioavailability and can be used for drugs that are poorly absorbed or ineffective when they are given orally. Some medications, such as certain antipsychotics, can be administered as long-acting intramuscular injections. The practice is often carried out through physical force in company of law-enforcement, and often against the will of the patient. However, all doses of long-acting antipsychotics injections are of at extreme risk to the health and well-being of the patient. Extreme ethical concerns should be considered. If the choice is made to use force, care should be taken to use only the smallest dose that is currently scientifically demonstrated to be efficacious for the specific drug. This is because, despite being injected, the drugs are designed with heavy esterifying molecular additions which can cause traces of the drugs to be found in circulation for up to one year. Ongoing IV infusions can be used to deliver continuous medication or fluids. Disadvantages of injections include potential pain or discomfort for the patient and the requirement of trained staff using aseptic techniques for administration. However, in some cases, patients are taught to self-inject, such as SC injection of insulin in patients with insulin-dependent diabetes mellitus. As the drug is delivered to the site of action extremely rapidly with IV injection, there is a risk of overdose if the dose has been calculated incorrectly, and there is an increased risk of side effects if the drug is administered too rapidly. Intranasal Drug administration via the nasal cavity yields rapid drug absorption and therapeutic effects. This is because drug absorption through the nasal passages doesn't go through the gut before entering capillaries situated at tissue cells and then systemic circulation and such absorption route allows transport of drugs into the central nervous system via the pathways of olfactory and trigeminal nerve. Intranasal absorption features low lipophilicity, enzymatic degradation within the nasal cavity, large molecular size, and rapid mucociliary clearance from the nasal passages, which explains the low risk of systemic exposure of the administered drug absorbed via intranasal. Sublingual Sublingual administration is fulfilled by placing the drug between the tongue and the lower surface of