Final answer:
In cases where patients cannot take oral medications, parenteral administration via intravenous or intramuscular injections is used, often in healthcare settings, to achieve higher plasma medication levels.
Step-by-step explanation:
For patients unable to take oral medications, the parenteral route of administration is indicated. This can include methods such as intravenous or intramuscular injections. This type of administration is usually performed in healthcare settings and is often preferred when a drug is not absorbed well in the gastrointestinal (GI) tract. The plasma levels achieved by intravenous administration are generally much higher than those achieved by oral or intramuscular administration. Hence, this route is particularly important when treating infections where high plasma levels of medication are crucial.