Dosages

Dosage refers to the amount of a drug or other substance to be taken at a given time, together with the planned schedule (route, frequency, duration). A dosing regimen seeks to achieve a therapeutic concentration in the body while minimizing adverse effects. Dosages are determined from pharmacokinetic and pharmacodynamic principles, alongside drug properties such as potency, bioavailability, and therapeutic index, and patient factors.

Dosing elements include the dose amount, route of administration, time interval, and total duration. Common practice uses standard labels in product information, but clinicians may adjust within approved ranges. Concepts such as a loading dose (an initial higher amount) and a maintenance dose (ongoing, smaller doses) are used for some regimens. Dose forms and routes (oral tablets, liquids, injections, inhalations) influence bioavailability and timing.

Patient-related factors influence dosing. Age, body weight or surface area, renal and hepatic function, pregnancy and lactation, genetics, and interacting medications can alter exposure and response. Special populations require tailored approaches: pediatrics often use weight- or age-based dosing; older adults may need lower starting doses and slower titration due to reduced clearance and comorbidity.

Calculation methods vary: mg/kg for weight-based dosing; mg/m^2 for body surface area in some chemotherapies; fixed doses for adults. Therapeutic drug monitoring may guide dosing for drugs with narrow therapeutic indices.

Safety and monitoring: prescribers balance efficacy and toxicity, adjust doses based on response and laboratory data, and educate patients on adherence and recognizing adverse effects. In case of suspected overdose, seek emergency care. Dose optimization continues throughout treatment as patient status changes.