Healthsetembro 25, 2023

What to look for and why it’s important to adjust drug dosing for patient-specific factors

When we look at labeling for drugs, we can see how often manufacturers recommend a one-size-fits-all, standardized dose in order to make things more streamlined for clinicians and patients. But every patient is different, and medications work differently inside different bodies, requiring a more nuanced, individualized approach to drug dosing.

Collaboration and evidence: Enhanced dosing for special populations

For healthcare professionals, evaluating every drug you wish to prescribe for each specific patient is important, but it is also a puzzle. You must balance the manufacturer’s dosing recommendations against your individual patient’s conditions, other medications they are taking, and additional factors influencing how they may process the drug to find an appropriate dose.

Collaboration between prescribers and pharmacists is essential to share expertise. It is also valuable to have access to an evidence-based drug decision support tool that focuses on enhanced dosing for special populations.

The role of a clinical pharmacy specialist in internal medicine

I spent more than six years as an internal medicine clinical pharmacy specialist at a hospital working alongside physicians on frontline patient care and patient education. I saw firsthand that prescribers aren’t always readily aware of the need for dose adjustments among special patient populations. This does not come from negligence or a lack of attention, but simply because it is a specialized knowledge that they can’t always know or be aware to look for, especially with a busy workload.

As the pharmacist on the team, I used to consider this my primary responsibility: making sure the drugs that our patients were receiving were dosed appropriately, taking into account whatever other disease states they might have or other medications they might be taking that could affect that dose.

Strategies for optimizing medication therapy: Where do you go when you have questions?

Nine times out of 10, any order the doctor places has to go through a pharmacist for it to end up with a patient. We are that gatekeeper who has to make the call on whether a dose needs to be adjusted to suit an individual patient’s needs.

Since it is impossible to know everything and healthcare is always evolving, these are the moments when enhanced dosing information becomes essential. A package insert may contain some basic information, but from a user perspective, the drug information within UpToDate® Lexidrug (formerly Lexicomp®) was always the first place I would check to provide a more extensive picture that incorporates the most recent data. Its enhanced dosing information puts to the forefront things that you might not have been considering when starting a drug or adjusting a dose for a special patient population when the answer might not be black-and-white. It also provides references to primary literature that can help you decide if this drug or dose is right for your patient.

Whenever I’m trying to determine the most appropriate medication dose for a patient, the information I’m often most interested in figuring out to help inform my decision is:

  • Who / what population was this drug studied in? Does my patient fall into this population?
  • What comorbidities does my patient have that might impact the medication choice and/or dose?

UpToDate Lexidrug would always save me time because I could easily navigate to the drug and quickly identify information on dose adjustments and additional references so I had what needed to make the best clinical decision for my patient.

The most common patient-specific factors that affect dosing

Some patient-specific factors frequently impact medication dosing and may increase the chance of side effects or treatment failure. Common patient traits likely to affect medications include:

  • Age
  • Weight
  • Kidney function
  • Liver function

Drug dosing in pediatrics and geriatrics

I had a pediatrics preceptor while in residency who would always say, “Kids are not just small adults;” pediatric patients cannot simply be given a proportionally lower dose than adults because they weigh less. This is because pediatric and neonatal patients process, metabolize, and respond to drugs very differently than adults.

Pediatric patients have different body composition, anatomy, and unique administration challenges from adult patients which impact medication selection and dose. Furthermore, medication safety and efficacy data are limited in the neonatal and pediatric population, making prescribing even more difficult.

It is vital that pharmacists have access to pediatric and neonatal drug information to assist with decisions in dosing this delicate population.

On the other end of that spectrum, it is also important to review and carefully consider the dosing of our older adult patient population as well. As patients age, they become more sensitive to side effects of different medications. They also are more prone to kidney and liver issues, which can impact the processing of medications.

There are far fewer studies that evaluate drugs in older adults, but pharmacists should always be aware of how certain drugs, particularly those that are impacted by the kidney and liver, might affect older adults very differently. Enhanced dosing data will have evidence to support your decision-making and provide the best available resources even when studies are scarce.

Dosing challenges for patients with high and low weights

While most clinicians are often aware of the dosing challenges associated with patients with obesity, similar challenges affecting patients at the extreme low end of the weight spectrum are less well thought of, but also warrant consideration.

Any patient with a non-average weight is likely to need a dosing adjustment but unlikely to have had someone of a comparable body type included in a given drug’s clinical trial. Most drugs are studied in what we tend to think of as an average population (typically 70 to 80 kilograms). Reviewing expert dosing analysis before making decisions for these patients is essential to help ensure medications are used effectively and that patients are not under- or overdosed based on their body weight.

UpToDate Lexidrug has also added enhanced dosing content for patients who have had bariatric surgery, which is a completely different consideration, as those patients have surgically altered stomach and intestines, where many drugs are absorbed. These bariatric surgery patients require a thoughtful and unique approach to medication dosing that has less to do with their body weight than how their post-surgical body is able to process and absorb certain medications.

Renal dosing adjustments

For most pharmacists, it’s likely ingrained in your mind to double check a patient’s renal function before dosing any drug.

But even when a patient doesn’t present with obvious signs or a chart diagnosis of kidney disease, renal function could still have an impact on medication disposition. It’s worth investigating further and considering a patient’s need for adjusted dosing if they present any signs that could be indicative of changes in kidney function. Those include:

  • Older patients, as kidney function declines with age.
  • Those taking other medications that may cause a decrease in kidney function.
  • Patients who may have recently recovered from kidney injury.

It’s up to the pharmacist to pause when a patient’s renal function situation may not be clearly understood or top of mind for physicians and nurses and take a moment to review if a dose adjustment is needed.

Limited availability of dosing recommendations for liver function

While healthcare professionals are conscientious of checking renal function when considering safe drug dosing, hepatic function and liver disease are less on the minds of most prescribers and even pharmacists.

The paucity of data regarding how hepatic function can impact drug dosing doesn’t change the fact that we could potentially be doing harm if we're not considering the effects of the liver on our patients’ outcomes. Lexidrug is working on collecting as much data as possible to add enhanced hepatic dosing content to its solutions, driving home the point that this is something that we as pharmacists should be thinking about for every single drug for every single patient.

Don’t forget the importance of ongoing monitoring and adjustments

When we make these patient-specific dosage adjustments, we hope to achieve more effective therapeutic outcomes and to reduce side effects.

We cannot forget that the extends beyond the initial dose.

I use the Monitoring Parameters field in Lexidrug drug monographs to help make a plan for following up on the patient’s progress. It’s another great gut check for providers if you, as a pharmacist, can say, “If we start this drug today, in two weeks, this is what we should expect to see to know that we’re on the right track.” It’s a way to close the loop on making sure that your patient’s ongoing safety is the priority.

Dosing is unique to every patient

Medication management for special populations can be really challenging, particularly as newer and more complicated drugs are approved. We must recognize that dosing is nuanced, and it is different for every patient – that what works for one might not be appropriate for another. While markers like age, weight, and kidney and liver function are major categories for potential dose adjustments, we should also keep ourselves open to additional categories and unique patient factors that may call for adjustment if need be. With a knowledge of medications, pharmacokinetics, and pathophysiology, as well as the valuable information synthesized in UpToDate Lexidrug, pharmacists are uniquely equipped to ensure safe and effective use of medications in all patients.

Learn More About UpToDate Lexidrug
Nisha Patel
Content Management Consultant for Clinical Effectiveness, Wolters Kluwer, Health
In her role, Nisha participates in the development and maintenance of adult monographs for key drug information referential databases, such as UpToDate® Lexidrug™, and synthesizes drug dosing content for customers.
UpToDate Lexidrug
Solução de referência de medicamentos baseada em evidências usada no fluxo de trabalho e em movimento
Os clínicos escolhem o UpToDate® Lexidrug™ para obter informações baseadas em evidências sobre medicamentos, a fim de apoiar decisões inteligentes e seguras sobre medicação. Estudos mostram que o Lexidrug é a solução de referência de medicamentos preferida para as equipes de cuidados.
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