ABSTRACT
The dose of a drug is the amount at the time of administration to obtain a desired therapeutic response, and the dosage regimen refers to the schedule of dosing. Generally, the manufacturer provides a range of doses for a given drug. Since several factors affect the dose of a drug, the exact amount of a drug to be administered is decided by the health care professionals. Some of the factors affecting the dose of a drug include the type of dosage form, route of drug administration, individual patient’s tolerance of the drug, genetic predisposition, concurrent administration of other drugs, patient’s age, body weight, gender, length of illness, general physical health, liver and kidney function in the patient, and the rate of absorption, distribution, metabolism and excretion of drugs in the patient. The dose of a given drug is specific to the patient. Thus, a fixed dose of a drug might be an overdose in some patients, whereas the same dose might be considered an under-dose in another group of patients. The inter-and intrasubject variations to the effects of drugs can be avoided by tailoring a dose (or a dosage regimen) to a given patient through the use of clinical pharmacokinetics. Thus, clinical pharmacokinetics may be defined as the applied science in which the pharmacokinetic principles are utilized for tailoring the dose and dosage regimen for an individual patient. The knowledge of clinical pharmacokinetics is essential in providing an optimum drug concentration at the receptor site to obtain the desired therapeutic response, and minimize the drug’s adverse or toxic effects.
