<P> Inhaled medications can be absorbed quickly and act both locally and systemically . Proper technique with inhaler devices is necessary to achieve the correct dose . Some medications can have an unpleasant taste or irritate the mouth . </P> <P> Inhalation by smoking a substance is likely the most rapid way to deliver drugs to the brain, as the substance travels directly to the brain without being diluted in the systemic circulation . The severity of dependence on psychoactive drugs tends to increase with more rapid drug delivery . </P> <P> The term injection encompasses intravenous (IV), intramuscular (IM), subcutaneous (SC) and intradermal (ID) administration . </P> <P> 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 . Ongoing IV infusions can be used to deliver continuous medication or fluids . </P>

Buccal administration is a parenteral route of administration