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30/10/2025, 18:21 Pharmaceutical Dosage Calculations

Pharmaceutical Dosage Calculations

Drug Dosing

The usual dose of a drug is the amount that ordinarily produces the desired
therapeutic response in the majority of patients.
The drug's usual dosage range is the range of dosage determined to be safe and
effective.

This provides the prescriber with dosing guidelines in initially selecting a drug
dose for a particular patient and the flexibility to change that dose as the
patient's clinical response warrants.
Usual doses are based on the results of clinical studies during the drug
development process as well as on clinical information gathered following the
initial approval and marketing of the drug (postmarketing surveillance).

Patient Parameters Affecting Dose Selection

For certain drugs and for certain patients, drug dosage is determined on the
basis of specific patient parameters.
These parameters include:

Age
Weight
Body surface area
Nutritional and functional status

Among patients requiring individualized dosage are:
Neonates and other pediatric patients
Elderly patients with diminished biologic functions
Individuals of all age groups with compromised liver and/or kidney function

(and thus reduced ability to metabolize and eliminate drug substances)
Critically ill patients
Patients being treated with highly toxic chemotherapeutic agents

NOTE: Certain drugs with a narrow therapeutic window often require
individualized dosing based on blood level determinations and therapeutic
monitoring.

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