It is reasonable to assume that all medicines taken by a patient are personalised to them. The doctor examines the patient, diagnoses the problem and writes a prescription for that individual person. The pharmacist reviews the prescription to ensure it is suitable for the patient, before dispensing it together with the appropriate advice, tailored for them.
However, in reality, other than the care taken in ensuring the medicine is appropriate for the patient, very little about the dosage is personalised. For most adult medicines with a wide therapeutic index, there is a standard dose, with alternative doses for children and for some medicines.
In the 1980s and 1990s, clinical pharmacokinetics emerged as a technique to assist in the dosing of medicines with narrow therapeutic indices. Pharmacists embraced this new science and used pharmacokinetics to individualise doses of medicines such as theophylline, gentamicin, digoxin and some anticonvulsants.
However, with the emergence of newer respiratory, cardiovascular and antiepileptic treatments, which had wider therapeutic indices, and the advent of once-daily dosing for gentamicin, there has been a decline in the routine use of this pharmacoscience. This edition of the journal carries an article on the application of pharmacokinetics to HAART therapy in the treatment of HIV, demonstrating once again the potential of applying this technique to modern medicines as a way of individualising patient treatment.
As with other medicines requiring careful dose titration, pharmacists can apply their broad scientific training to this area of treatment and make a significant contribution to patient care.
As well as the revitalisation of an established pharmacoscience, this edition also carries a feature, the report from the ESCP conference, on the emergence of two other pharmacosciences, pharmacogenetics and pharmacogenomics. These are also aimed at personalising medicines.
Pharmacogenetics is the technique of identifying the gene sequence that can predict response to drug therapy. As the conference report points out, the routine application of pharmacogenetics is still a long way off. On the other hand, pharmacogenomics, which uses the variability in gene expression to help inform response to drug therapy, is already with us.
For example, trastuzamab can now be targeted at HER2-positive breast cancer patients, thus improving the likelihood of therapeutic success. Notwithstanding the subtle differences between the techniques, both will allow the individualisation of medicines for patients, just as pharmacokinetics does. The tests to show individual genetic variation in response to drug therapy will no doubt be developed and managed through laboratories outside the pharmacy.
However, this does not mean pharmacists should not be involved in the application of this information to individual patients. The situation is not dissimilar to pharmacokinetics, where in the majority of situations the actual serum concentration measurements are processed in the pathology or microbiology laboratory. However, this has not stopped pharmacists becoming experts in the interpretation and application of drug level results in clinical practice (clinical pharmacokinetics). I believe similar opportunities exist in relation to pharmacogenetics and pharmacogenomics.
Although the routine application of these techniques is still in the future, pharmacists should begin to develop an understanding of these techniques now, particularly as we take on prescribing roles in the future. Our universities should begin the process at undergraduate level, as they train the pharmacists of tomorrow. A thorough understanding of all pharmacosciences will help us as a profession to truly personalise individual patients’ medicines.
Ray Fitzpatrick,
Consultant Editor
