Which category of drugs is designed to restore a normal body substance that is deficient or not produced, such as hormone replacement after organ removal?

• A. Therapeutic drugs
• B. Prophylactic drugs
• C. Replacement drugs
• D. Diagnostic drugs

Answer: (C)

Replacement drugs are designed to substitute for a normal body substance that is deficient or no longer produced. They bring the body back to its usual chemical balance, such as insulin after pancreas failure or thyroid hormone after removal of the thyroid. This differs from therapeutic drugs, which treat a disease or its symptoms without replacing a missing substance; prophylactic drugs prevent disease; and diagnostic drugs are used to aid in diagnosing conditions rather than replace a substance.