Indication: what it is for
An indication is the medical reason a drug is used — the condition it is approved to prevent, treat, or relieve. Ibuprofen is indicated for pain, fever, and inflammation. A single drug may have several indications, and regulators approve each one only after evidence shows benefit. Using a drug for a purpose it was not approved for is called off-label use — sometimes reasonable and common, but a decision made deliberately, not by accident.
Dose: how much, how often
The dose is the amount of drug given, and the study of dosing is posology. A dose statement is never just a number — it specifies the amount, the route, and the frequency, for example '500 mg by mouth every 8 hours'. The right dose lives inside the therapeutic window: high enough to work, low enough to stay safe. For many drugs the dose is found by dose titration — starting low and adjusting upward to each patient's response.
Worked dose calculation (weight-based) -------------------------------------- Drug ordered: 15 mg/kg every 6 hours Child weighs: 20 kg Single dose = 15 mg/kg x 20 kg = 300 mg Frequency = every 6 hours = 4 doses/day Daily total = 300 mg x 4 = 1200 mg/day Always check the daily total against the maximum.
Mechanism: how it works
The mechanism of action is the molecular story of how a drug produces its effect: which target it binds and what changes as a result. Ibuprofen, for instance, blocks an enzyme that makes inflammatory signals, so pain and swelling fall. Knowing the mechanism is what lets us group drugs into a drug class, predict their side effects, and reason about therapeutics rather than memorising each drug in isolation.