Posology

The word posology is derived from the greek words 'posos' meaning how much and 'logos' meaning science. That means it is a branch of medical science which deals with does or quantity of drugs which can be administered to produce the required pharmacological actions.
         The does of a drug may be defined as the quantity of drug which is "enough but not, too much" the idea is to produce the drug's optimum therepeutic effect in a particular patient with the lowest possible does. the pharmacopoeias and eltextbooks usually give a minimum and maximum does for each drug. minimum does is necessary to produce a desired therapeutic effect but maximum dose is the largest quantity which can be given safely to an indi idual without producing harmful effects l.Beyound the maximum does certain toxic effects and undesirable effects may be produced.
        The does of a drug cannot be fixed rigidly because there are so many factors which influence the doses. eg.. age, condition of the patient, severity of the disease
       The does mentioned in the table represent the average maximum quantities of drufs which can be administered to an adult orally within 24 hours; when other routes of administration are followed the relevant appropriate dose is mentioned. if the does are to be administered in divided does, the frequencies of administration are stated.
         The does viven here are for general guidance. it is the responsibility of the prescriber regardinv the amount of druv prescribed or the frequency at which the drug is administered. but before dispensing any medication it is the duty of the pharmacist to satisfy himself that overdoes has not been pres ribed. in case of doubt he should consult the prescriber and to confirm the does of individual medicaments he can consult the extra pharmacopoeia.