Precision dosing takes shape

What do you do when you read a drug label and the dosing information doesn’t apply? You have a child in pain and the dose for the analgesic is given for a 2-year-old and a 4-year-old, but she is 3. What do you do? Do you opt for the higher dose or the lower one? And isn’t the child’s body mass a more relevant metric than her age? Clinicians face similar conundrums on a regular basis.

The drug development process includes three phases of clinical trials prior to regulatory approval, each with different goals. During the last phase — Phase III — the drug is given to large groups of people to confirm its effectiveness, monitor any side-effects, compare it with commonly used treatments and collect information that will allow it to be used safely.

Phase III studies involve randomised and blind testing in several hundred to several thousand ‘typical’ patients. Accordingly, the directions on the drug label are geared to that typical patient population. More complex cases — paediatric and geriatric patients, pregnant women and patients with impaired liver or kidney function — are usually excluded from these trials.

Furthermore, each of these special populations has more complex challenges in determining drug performance. For example, paediatric cases are complicated because absorption rates and enzyme levels change as their bodies mature, whereas geriatric patients are often being treated for multiple conditions simultaneously, making it harder to track the impact of an individual drug.

That said, these specific patient populations could benefit from the drug being tested. If the drug is ultimately approved by a regulatory agency, how does a clinician know what dose to prescribe to a member of one of these untested patient populations? There is no label information to help, so any prescribing has to be done off-label with the drug dosing based on practice, not science.