Final answer:
Intravenous and possibly Intramuscular injections fall outside the scope of an unlicensed medical assistant's practice, while Subcutaneous and Intradermal injections might be allowed if properly trained. For home administration of antibiotics, oral routes are typically preferred unless intravenous administration is necessary for higher plasma drug levels.
Step-by-step explanation:
The parenteral routes of administration that are outside the unlicensed medical assistant's scope of practice include Intravenous (C) and possibly Intramuscular (A), depending on state regulations. Unlicensed medical assistants typically cannot perform these procedures as they require specialized training and qualifications that licensed medical professionals possess. Subcutaneous (B) and Intradermal (D) injections may be within their scope of practice in some jurisdictions if they have received proper training and certification. Regarding the administration of an antimicrobial to treat a systemic infection, parenteral routes such as intravenous administration can provide higher plasma levels of a drug compared to oral or intramuscular administration. This is important when treating serious infections where high plasma levels of antibiotics are needed quickly. In a home setting, oral administration (A) is typically most appropriate and convenient for patients unless the antimicrobial is poorly absorbed in the gastrointestinal tract or when high plasma levels are necessary.