Final answer:
Parenteral routes, such as intramuscular and intravenous injections, should be used for administering drugs that stain teeth to avoid direct contact with the oral cavity. For treating systemic infections at home, oral administration is generally convenient, but intravenous may be necessary for severe cases.
Step-by-step explanation:
To minimize the risk of staining teeth, drugs known to have this side effect should be administered in a manner that reduces direct contact with the teeth. Parenteral routes, such as intramuscular (IM) and intravenous (IV) injections, are preferred for drugs that can cause discoloration of teeth, since these methods deliver the medication directly into the bloodstream and avoid exposure to the oral cavity.
In the context of treating systemic infections with antimicrobials, the route of administration depends on factors like the severity of the infection, the drug's absorption and distribution characteristics, and whether home administration is feasible. While oral administration (A) is often the most convenient for home treatment, intravenous administration (B) may be necessary for severe infections or when high plasma levels of the drug are required. Topical (C) application is only suitable for localized infections, and parenteral (D) routes are generally preferred when oral administration is inadequate or not possible.