Drug, dosage, activity, studies of antimalarials by physical methods - II

Studies pertaining to drug-DNA interactions in treating a disease efficiently have taken an important place in recent times. Murthy and colleagues were active in correlating the drug activity, with physical parameters like refractivity, susceptibility, molecular electron ionization cross-section and the dosage. The molecular polarizability, diamagnetic susceptibility and molecular electron ionization cross section Q have been evaluated. An analysis of Q in the light of the data available on plasma protein binding, bio availability, Log P and half-Life show semblance of regular dependence of Q on them and hence an effort is made to bring this dependence into a regular mathematical relationship. The dosage of each drug is calculated. A critical look at the results arrived on Q and dosages reveal that a highly active drug with large Q need to be monitored in very small quantities and any minute increase in dosage is resulting in unwanted toxic effects and vice versa. The algebraic formulae enable one to calculate the dosages theoretically from the value of Q and other parameters and the calculated dosage through the formulae agreed favorably well with suggested dosages. For example, in primaquine phosphate, the calculated dosage is 30 mg per day against the suggested practical dosage of 26.3 mg per day. A similar observation is made in mepacrine with theoretical dosage of 60 mg per day as against the suggested practical dosage of 100 mg per day. In short, the molecular structure followed by refraction and susceptibility measurements and Q will throw light on dosage, toxicity of a drug. Thus the present investigations pave way for a new direction of approach for study of drug activity without recourse to techniques involving highly expensive instrumentation and highly theoretical approaches involving quantum mechanical methods.