text: Types of absorption in pharmacokinetics include the following:
  * Instantaneous absorption: absorption is nearly immediate. A common example is bolus intravenous injection.
  * Zero-order absorption: rate of absorption is constant. A common example is continuous intravenous infusion.
  * First-order absorption: rate of absorption is proportional to the amount of drug remaining to be absorbed. Representative examples include typical cases of oral administration, subcutaneous injection, and intramuscular injection.