Drug dosing in the critically ill obese patient: a focus on medications for hemodynamic support and prophylaxis

[Translated article] Drug dosing in obese critically ill patients, a literature review

INTRODUCTION

Obesity constitutes a global public health problem, and knowledge about drug dosing in obese patients is limited. Clinical trials in critically ill patients rarely include obese individuals, resulting in a lack of specific dosing information in product data sheets. The aim of this literature review is to provide clinicians with efficient and safe guidelines for this group of patients.

METHODS

A multidisciplinary group composed of pharmacists specialised in hospital pharmacy and physicians specialised in intensive care medicine was formed. The therapeutic groups and, in depth, the most commonly used active ingredients in the intensive care unit were identified and reviewed. The bibliographic review was carried out using terms such as: "obese", "overweight", "critical illness", "drug dosification", and "therapeutic dose monitoring". All the information was evaluated by the working group, which reached a consensus on dosing recommendations for each drug in obese critically ill patients.

RESULTS

Eighty three drugs belonging to the following therapeutic groups were identified: antivirals, antibacterials, antifungals, immunosuppressants, antiepileptics, vasopressors, anticoagulants, neuromuscular blocking agents, and sedatives. A table with the consensus dosing recommendation for each of these was produced after review.

CONCLUSIONS

Drug dosing in obese patients, both in critical and non-critical settings, remains an area with significant uncertainties. This review provides updated and exhaustive information on the dosing of the main therapeutic groups in obese critically ill patients, and is a useful tool for both physicians in critical care units and clinical pharmacists in their practice in this setting.

Drug dosing in obese critically ill patients, a literature review

INTRODUCTION

The prevalence of obesity represents a significant global public health challenge, and the available evidence concerning the appropriate dosing of pharmaceutical in patients with obesity is limited. It is uncommon for clinical trials in critically ill patients to include obese individuals, which results in a lack of specific dosing information in product data sheets. The objective of this literature review is to provide clinicians with efficacious and secure guidelines for this cohort of patients.

METHODS

A multidisciplinary team comprising pharmacists specialized in hospital pharmacy and physicians with expertise in intensive care medicine was established. The therapeutic groups and, in particular, the most commonly used active ingredients within the Intensive Care Unit were identified and subjected to detailed analysis. The following terms were included in the search: "obese", "overweight", "critical illness", "drug dosification", and "therapeutic dose monitoring". All the information was then evaluated by the working group, which reached a consensus on the dosing recommendations for each drug in obese critically ill patients.

RESULTS

A total of 83 drugs belonging to the following therapeutic groups were identified: antivirals, antibacterials, antifungals, immunosuppressants, antiepileptics, vasopressors, anticoagulants, neuromuscular blocking agents and sedatives. A table was produced containing the consensus dosing recommendations for each of the aforementioned drugs following a review of the available evidence.

CONCLUSIONS

Drug dosing in obese patients, both in critical and noncritical settings, remains an area with significant uncertainty. This review provides comprehensive and up-to-date information on the dosing of the main therapeutic groups in obese critically ill patients, offering a valuable resource physicians in critical care units and clinical pharmacists in their practice in this setting.

Ten take-home messages on vasopressin use in critically ill patients

The most used vasopressors in critically ill patients are exogenous catecholamines, mainly norepinephrine. Their use can be associated with serious adverse events and even increased mortality, especially if administered at high doses. In recent years, the addition of vasopressin has been proposed to counteract the deleterious effects of high doses of catecholamines (decatecholaminization) with the intention of improving the prognosis of these patients. Currently, vasopressin has two main indications: septic shock and vasoplegic shock in the postoperative period of cardiac surgery. In septic shock, current evidence favors its early initiation before reaching high doses of norepinephrine. In the postoperative period of cardiac surgery, the different benefits of the use of vasopressin have been studied, especially in patients with atrial fibrillation and pulmonary hypertension. When used properly, vasopressin is a safe an effective drug for the indications described above.

Clinical pharmacokinetics of antimicrobials in critical care: a narrative review

INTRODUCTION

The management of critically ill septic patients presents considerable challenges due to multifaceted physiological alterations. Rapid changes such as fluid shifts, hyperdynamic states, and altered renal clearance often require special attention for better clinical outcomes. Vital organ dysfunction, with or without MODS, often necessitates supportive management like RRT, ventilatory support, and ECMO. These interventions can significantly affect the PK/PD of administered antimicrobials, complicating effective treatment.

AREA COVERED

Patient-specific parameters such as age, weight, and comorbid illnesses (e.g. cystic fibrosis, burns, and immunocompromised states) are critical determinants of antimicrobial pharmacokinetics. Understanding PK/PD determinants is crucial for developing optimized dosing regimens that enhance therapeutic efficacy and minimize toxicity in critically ill patients.

EXPERT OPINION

Incorporating pharmacometrics approaches in dose optimization can significantly improve patient outcomes. This review focuses on the nuances of PK/PD for optimized antimicrobial dosing in critically ill septic patients, emphasizing the importance of individualized treatment plans to address the complex and dynamic needs of this patient population. The adoption of these advanced pharmacokinetic and pharmacodynamic principles into clinical practice is essential for advancing patient care and optimizing therapeutic outcomes in critically ill patients.

The impact of sugammadex dosing and administration practices on potential cost savings for pharmacy departments

PURPOSE

Neuromuscular blocking agents (NMBAs) are commonly used during surgery, and restoring neuromuscular function at the end of surgery is vital in preventing complications of residual paralysis. Recent guidelines from the American Society of Anesthesiology recommend using sugammadex over neostigmine; however, sugammadex is significantly more expensive than neostigmine and may increase drug expenditure for pharmacy departments. This review summarizes evidence evaluating sugammadex dose adjustments and the potential of these dose adjustments to lead to cost savings for pharmacy departments.

SUMMARY

We found evidence suggesting that the manufacturer-recommended sugammadex dose may not be needed in many patients and that dosing based on an adjusted body weight or based on depth of neuromuscular blockade may lead to lower sugammadex usage. Combining sugammadex with neostigmine could also decrease the dose of sugammadex required. We have highlighted the importance of objective neuromuscular monitoring to guide sugammadex dosing and evaluation for residual neuromuscular blockade. Cost savings for pharmacy departments may be realized by these alternative dosing strategies and/or vial-splitting practices.

CONCLUSION

Implementing practices related to sugammadex vial splitting and dose adjustment based on body weight and depth of neuromuscular blockade shows potential benefits in terms of sugammadex cost savings.

Joint effect of atrial fibrillation and obesity on mortality in critically ill patients

BACKGROUND

The interplay between atrial fibrillation (AF) and obesity on mortality in critically ill patients warrants detailed exploration, given their individual impacts on patient prognosis. This study aimed to assess the associations between AF, obesity, and 1-year mortality in a critically ill population.

METHODS

Utilizing data from the Medical Information Mart for Intensive Care (MIMIC)-IV database, we conducted a retrospective analysis of adult patients admitted to the intensive care unit. The primary endpoint was 1-year mortality, analyzed through Cox regression with hazard ratio (HR) and Kaplan-Meier survival methods.

RESULTS

The study included 25,654 patients (median age 67.0 years, 40.6% female), with 39.0% having AF and 36.1% being obese. Multivariate COX regression analysis revealed that AF was associated with a 14.7% increase in the risk of 1-year mortality (p < 0.001), while obesity was linked to a 13.9% reduction in mortality risk (p < 0.001). The protective effect of obesity on mortality was similar in patients with (HR = 0.85) and without AF (HR = 0.86). AF led to a slightly higher risk of mortality in patients without obesity (HR = 1.16) compared to those with obesity (HR = 1.13). Kaplan-Meier survival curves highlighted that non-obese patients with AF had the lowest survival rate, whereas the highest survival was observed in obese patients without AF.

CONCLUSIONS

AF significantly increased 1-year mortality risk in critically ill patients, whereas obesity was associated with a decreased mortality risk. The most adverse survival outcomes were identified in non-obese patients with AF.

asopressin nitiation as a econd-Line Vasoressor in Early eptic hock (VISPSS)

BACKGROUND

Vasopressin is recommended as a second-line vasoactive agent for the management of septic shock; however, a paucity of data to guide its optimal use remains. The aim was to evaluate the effect of time-to vasopressin initiation and norepinephrine (NE) dose at vasopressin initiation on clinical outcomes in patients presenting with septic shock.

METHODS

This was a multi-centered, retrospective, observational study conducted in patients with septic shock. Patients were divided into 2 groups: patients initiated on vasopressin when NE-equivalent dose (NEE) < 0.25 mcg/kg/min or ≥ 0.25 mcg/kg/min. The primary outcome was time-to-vasopressor discontinuation (hours). Secondary outcomes included 28-day in-hospital mortality, intensive care unit (ICU) length of stay (LOS), fluid balance after 72 hours, and the change in NEE at 12 hours.

RESULTS

A total of 302 patients were included in this study. After propensity-score matching, 73 patients in each group were identified for analysis. There was no significant difference in the time-to-vasopressor discontinuation (hours) between the groups (88.8 [55-187.5] vs 86.7 [47-172]); p = 0.7815). Fluid balance (mL) at 72 hours was significantly lower when vasopressin was initiated at NEE < 0.25 mcg/kg/min (1769 [71-7287] vs 5762 [1463-8813]; p = 0.0077). A multivariable linear regression showed shorter time to shock resolution with earlier vasopressin initiation, defined as within 4 hours (p < 0.05).

CONCLUSION

In this propensity-score matched cohort, vasopressin initiation at NEE < 0.25 mcg/kg/min was not associated with shorter vasopressor duration. There was a lower fluid balance at 72 hours when vasopressin was initiated at lower NE doses.

Implementation and Evaluation of Weight-Based Vasopressors in Intensive Care Units

Background: Vasopressors, including norepinephrine, epinephrine, and phenylephrine are commonly used to maintain mean arterial pressure (MAP) in critically ill patients. Despite their frequent use, the optimal dosing strategy for vasopressors remains understudied. Objective: The purpose of this study is to evaluate the implementation of a weight-based (WB) dosing strategy using ideal body weight compared to a non-weight-based (NWB) dosing strategy for vasopressors in critically ill patients. Methods: This is a retrospective chart review of patients admitted to intensive care units receiving vasopressor medications for greater than or equal to 4 hours. Patients received either an NWB or a WB vasopressor dosing strategy. The primary endpoint was the time to achieve goal MAP. Results: This study included 153 patients in the NWB vasopressor dosing group and 183 in the WB dosing group. The median time to achieve goal MAP in the NWB group was 24 minutes versus 21 minutes in the WB group (P = 0.1713). There were no significant differences in secondary outcomes including number of vasoactive agents required, hospital length of stay, and duration of mechanical ventilation. Subgroup analysis of patients with extremes of body mass index did not show a difference in time to achieve goal MAP. In a subgroup analysis of patients with septic shock, a higher percentage of patients in the WB group received corticosteroids than the NWB group patients (14% vs. 54%; P ≤ 0.001). Conclusion and relevance: There was no difference in time to achieve goal MAP when using a WB or NWB vasopressor dosing approach. Institutions should employ a consistent dosing strategy for vasopressors with either an NWB or WB approach.

Direct oral anticoagulants and the risk of adverse clinical outcomes among patients with different body weight categories: a large hospital-based study

OBJECTIVE

Through predictable pharmacokinetics-including a convenient fixed-dose regimen, direct oral anticoagulants (DOACs) are preferred over previous treatments in anticoagulation for various indications. However, the association between higher body weight and the risk of adverse consequences is not well studied among DOAC users. We aim to explore the association of body weight and adverse clinical outcomes in DOAC users.

METHODS

A total of 97,413 anonymised DOAC users in a tertiary care setting were identified following structured queries on the electronic health records (EHRs) to extract the feature-rich anonymised dataset. The prepared dataset was analysed, and the features identified with machine learning (ML) informed the adjustments of covariates in the multivariate regression analysis to examine the association. Kaplan-Meier analysis was performed to evaluate the mortality benefits of DOACs.

RESULTS

Among DOAC users, the odds of adverse clinical outcomes, such as clinically relevant non-major bleeding (CRNMB), ischaemic stroke, all-cause mortality, and prolonged hospital stay, were lower in patients with overweight, obesity, or morbid obesity than in patients with normal body weight. The odds of ischaemic stroke (OR 0.42, 95% CI: 0.36-0.88, p = 0.001) and all-cause mortality (OR 0.87, 95% CI: 0.81-0.95, p = 0.001) were lower in patients with morbid obesity than in patients with normal body weight. In the Kaplan-Meier analysis, apixaban was associated with a significantly lower rate of mortality overall and in obesity and overweight subgroups than other DOACs (p < 0.001). However, rivaroxaban performed better than apixaban in the morbid obesity subgroup (p < 0.001).

CONCLUSION

This study shows the positive effects of DOAC therapy on clinical outcomes, particularly in patients with high body weight. However, this still needs validation by further studies particularly among patients with morbid obesity.

Prescribing Practices for Agitation Medication in Obese Patients Admitted to the Emergency Department

INTRODUCTION

Weight is a factor that influences the dosages of many medications, although no clinical studies have evaluated this factor in the use of agitation medications in the obese population. The objectives of this study were to assess the need for weight considerations in dosing antipsychotics and benzodiazepines for patients with agitation and to assess prescribing patterns in agitated patients.

METHODS

This retrospective cohort study compared outcomes between obese and nonobese adult patients who received at least one parenteral administration of an antipsychotic or benzodiazepine for agitation in the emergency department. The primary outcomes were total antipsychotic and benzodiazepine doses within 24 hours (in chlorpromazine equivalents and lorazepam equivalents, respectively). Key secondary outcomes included antipsychotic and benzodiazepine doses used for first administration, incidence of repeat emergency medication administration within 24 hours, time to next administration, and number of repeat administrations within 24 hours.

RESULTS

The study examined 115 patient encounters in each cohort of patients in the study. The baseline characteristics of the 2 study cohorts were similar. Both groups had similar mean 24-hour antipsychotic usage [272.7 chlorpromazine equivalents (nonobese cohort), 313.5 chlorpromazine equivalents (obese cohort); P=0.157] and mean 24-hour benzodiazepine usage [0.9 lorazepam equivalents (both cohorts); P=0.750]. Differences between the study cohorts on all of the secondary outcomes were also not statistically significant (P>0.05).

DISCUSSION

This study did not find the use of higher dosages of agitation medication in the obese compared with the nonobese population. Future prospective trials, with possible emphasis on individual medications, specific etiologies of agitation, or morbid obesity, are required to confirm this finding or to elucidate potential differences in optimal medication dosages for the obese population.

Comparison of Drug-Related Problems in COVID-19 and Non-COVID-19 Patients Provided by a German Telepharmacy Service for Rural Intensive Care Units

Telepharmacy is used to bridge the persisting shortage of specialist ward-based pharmacists, particularly in intensive care units (ICU). During the coronavirus disease 2019 (COVID-19), pharmacotherapy was rapidly developed, which resulted in multiple changes of guidelines. This potentially led to a differing risk for drug-related problems (DRPs) in ICUs. In this study, DRPs were detected in telepharmacy consultations of a German state-wide telemedicine network for adult patients in rural ICUs. The analysis included ICUs of ten general care hospitals with a total of 514 patients and 1056 consultations. The aim of this retrospective, observational cohort study was to compare and analyze the DRPs resulting from ICU patients with or without COVID-19. Furthermore, known risk groups for severe COVID-19 progression (organ insufficiency [kidney, liver], obesity, sex, and/or older age) were investigated with their non-COVID-19 counterparts. As a result, in both groups patients with acute renal insufficiency and without renal replacement therapy showed a significantly higher risk of being affected by one or more DRPs compared to patients with normal renal function. In COVID-19 patients, the initial recommendation of therapeutic anticoagulation (ATC-code B01AB 'Heparin group') resulted in significantly more DRPs compared to non-COVID-19 patients. Therefore, COVID-19 patients with therapeutic anticoagulation and all ICU patients with renal insufficiency should be prioritized for telepharmacy consultations.

A Real-World Exploration into Clinical Outcomes of Direct Oral Anticoagulant Dosing Regimens in Morbidly Obese Patients Using Data-Driven Approaches

INTRODUCTION

The clinical outcomes of direct oral anticoagulant (DOAC) dosage regimens in morbid obesity are uncertain due to limited clinical evidence. This study seeks to bridge this evidence gap by identifying the factors associated with clinical outcomes following the dosing of DOACs in morbidly obese patients.

METHOD

A data-driven observational study was carried out using supervised machine learning (ML) models with a dataset extracted from electronic health records and preprocessed. Following 70%:30% partitioning of the overall dataset via stratified sampling, the selected ML classifiers (e.g., random forest, decision trees, bootstrap aggregation) were applied to the training dataset (70%). The outcomes of the models were evaluated against the test dataset (30%). Multivariate regression analysis explored the association between DOAC regimens and clinical outcomes.

RESULTS

A sample of 4,275 morbidly obese patients was extracted and analysed. The decision trees, random forest, and bootstrap aggregation classifiers achieved acceptable (excellent) values of precision, recall, and F1 scores in terms of their contribution to clinical outcomes. The length of stay, treatment days, and age were ranked highest for relevance to mortality and stroke. Among DOAC regimens, apixaban 2.5 mg twice daily ranked highest for its association with mortality, increasing the mortality risk by 43% (odds ratio [OR] 1.430, 95% confidence interval [CI] 1.181-1.732, p = 0.001). On the other hand, apixaban 5 mg twice daily reduced the odds of mortality by 25% (OR 0.751, 95% CI 0.632-0.905, p = 0.003) but increased the odds of stroke events. No clinically relevant non-major bleeding events occurred in this group.

CONCLUSION

Data-driven approaches can identify key factors associated with clinical outcomes following the dosing of DOACs in morbidly obese patients. This will help design further studies to explore well tolerated and effective DOAC doses for morbidly obese patients.

Critical care for multimorbid patients

Multimorbidity - the simultaneous presence of several chronic diseases - is very common in the critically ill patients. Its prevalence is roughly 40-85 % and continues to increase further. Certain chronic diseases such as diabetes, obesity, chronic heart, pulmonary, liver or kidney disease and malignancy are associated with higher risk of developing serious acute complications and therefore the possible need for intensive care. This review summarizes and discusses selected specifics of critical care for multimorbid patients.

Evaluation of phenytoin loading doses in overweight patients using actual versus adjusted body weight

BACKGROUND AND OBJECTIVES

The appropriate loading dose strategy for phenytoin/fosphenytoin in overweight patients is unknown. A small pharmacokinetic study indicated that overweight patients have a higher volume of distribution and potentially would benefit from using adjusted body weight (AdjBW) instead of actual body weight (ABW) to calculate the loading dose. The purpose of this study was to determine the optimal loading dose strategy of phenytoin in patients whose ABW is greater than 120% of their ideal body weight (IBW) using either ABW or AdjBW for calculation of the loading dose.

METHODS

This was a single center, retrospective study which included patients who received a loading dose of phenytoin of at least 10 mg/kg based on ABW, had a phenytoin level drawn <6 h after the end of the dose, and weighed ≥120% of their IBW. Patients were excluded if they received intramuscular phenytoin or fosphenytoin or were prescribed phenytoin prior to the loading dose. Patients were divided into two groups, those who were dosed using their AdjBW versus those dosed using ABW. The primary outcome was achievement of therapeutic phenytoin level of 10-20 mcg/mL. Secondary outcomes included achievement of a subtherapeutic or supratherapeutic level.

RESULTS

A total of 195 patients (128 in AdjBW group and 67 in ABW group) met criteria for inclusion. Patients in the AdjBW group weighed more (96.2 kg vs. 91.2 kg, p = 0.04) and received a lower dose in milligrams (1364 vs. 1760, p < 0.0001) and in mg/kg of ABW (14.2 vs. 19.3, p < 0.0001). The primary outcome was achieved in 74% of patients in the AdjBW group and 57% of patients in the ABW group (p = 0.02). Patients in the ABW group were more likely to have a supratherapeutic level (43% vs. 22%, p = 0.003), although adverse reactions did not differ between the groups.

DISCUSSION

Patients weighing >120% of their IBW (average body mass index 33.5 kg/m²) who received a 20 mg/kg loading dose based on AdjBW were more likely to achieve a therapeutic phenytoin concentration compared to those dosed based on ABW. Further research is needed to correlate this finding with clinical outcomes, such as resolution of status epilepticus.

Dosing Medications for Coagulopathy Reversal in Patients with Extreme Obesity

BACKGROUND

The reversal of anticoagulant or antiplatelet medications is a priority in the management of patients with severe injury with the goal of minimizing further bleeding without thrombotic complications. There are few studies, however, evaluating the dosing of reversal agents in the setting of trauma specific to patients with extreme obesity. Nevertheless, clinicians must still make decisions, balancing concerns of ongoing bleeding with excessive thrombosis.

OBJECTIVES

We describe the literature pertaining to dosing of medications used for the reversal of both drug-induced and trauma-related coagulopathy with the intent of providing a framework for clinicians to make dosing decisions in this challenging population.

DISCUSSION

Obesity is known to impact both the volume of distribution and the clearance of medications, but these changes are not usually linear with size nor are they uniform across drugs. Current strategies for dosing reversal agents in obesity include a capped dose (e.g., prothrombin complex concentrates), fixed dosages (e.g., andexanet alfa, idarucizumab, and tranexamic acid), and weight-based dosing (e.g., desmopressin). Extreme obesity, however, was not highly prevalent in the studies that have validated these dosing strategies. In fact, many of the clinical studies fail to report the average weight of the patients included.

CONCLUSION

Future studies should make efforts to increase reporting of patients with obesity included in clinical trials along with results stratified by weight class. In the meantime, doses listed in product labels should be used. Desmopressin should be dosed using either ideal body weight or a dose-capping strategy.

Dexamethasone exposure in normal-weight and obese hospitalized COVID-19 patients: An observational exploratory trial

During the latest pandemic, the RECOVERY study showed the benefits of dexamethasone (DEX) use in COVID-19 patients. Obesity has been proven to be an independent risk factor for severe forms of infection, but little information is available in the literature regarding DEX dose adjustment according to body weight. We conducted a prospective, observational, exploratory study at Geneva University Hospitals to assess the impact of weight on DEX pharmacokinetics (PK) in normal-weight versus obese COVID-19 hospitalized patients. Two groups of patients were enrolled: normal-weight and obese (body mass index [BMI] 18.5-25 and >30 kg/m2 , respectively). All patients received the standard of care therapy of 6 mg DEX orally. Blood samples were collected, and DEX concentrations were measured. The mean DEX AUC0-8 and Cmax were lower in the obese compared to the normal-weight group (572.02 ± 258.96 vs. 926.92 ± 552.12 ng h/ml and 138.67 ± 68.03 vs. 203.44 ± 126.30 ng/ml, respectively). A decrease in DEX AUC0-8 of 4% per additional BMI unit was observed, defining a significant relationship between weight and DEX AUC0-8 (p = 0.004, 95% CI 2-7%). In women, irrespective of the BMI, DEX AUC0-8 increased by 214% in comparison to men (p < 0.001, 95% CI 154-298%). Similarly, the mean Cmax increased by 205% in women (p < 0.001, 95% CI 141-297%). Conversely, no significant difference between the obese and normal-weight groups was observed for exploratory treatment outcomes, such as the length of hospitalization. BMI, weight, and gender significantly affected DEX AUC. We conclude that dose adjustment would be needed if the aim is to achieve the same exposures in normal-weight and obese patients.

Pitfalls and pearls with drug dosing in the critically ill obese patient: 10 statements to guide ICU practitioners

Obesity is highly prevalent in ICU patients presenting a number of challenges, one of which is drug dosing. There are limited high-quality data describing drug dosing in obesity, which can lead to dosing strategies that are suboptimal. For example, inappropriately using the wrong weight for weight-based dosing can lead to supratherapeutic drug concentrations and an adverse drug event or subtherapeutic drug concentrations and treatment failure. A generalized framework for decision making specific for obese patients is available that describes a step-by-step approach for constructing dosing regimens. This manuscript will build on that framework by providing pitfalls and pearls for clinicians to consider when making dosing decisions in critically ill patients with severe obesity.

Drug dosing in hospitalized obese patients with COVID-19

Obesity is highly prevalent in hospitalized patients admitted with COVID-19. Evidence based guidelines are available for COVID-19-related therapies but dosing information specific to patients with obesity is lacking. Failure to account for the pharmacokinetic alterations that exist in this population can lead to underdosing, and treatment failure, or overdosing, resulting in an adverse effect. The objective of this manuscript is to provide clinicians with guidance for making dosing decisions for medications used in the treatment of patients with COVID-19. A detailed literature search was conducted for medications listed in evidence-based guidelines from the National Institutes of Health with an emphasis on pharmacokinetics, dosing and obesity. Retrieved manuscripts were evaluated and the following prioritization strategy was used to form the decision framework for recommendations: clinical outcome data > pharmacokinetic studies > adverse effects > physicochemical properties. Most randomized controlled studies included a substantial number of patients who were obese but few had large numbers of patients more extreme forms of obesity. Pharmacokinetic data have described alterations with volume of distribution and clearance but this variability does not appear to warrant dosing modifications. Future studies should provide more information on size descriptors and stratification of data according to obesity and body habitus.

Implications of obesity for drug administration and absorption from subcutaneous and intramuscular injections: A primer

DISCLAIMER

In an effort to expedite the publication of articles related to the COVID-19 pandemic, AJHP is posting these manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time.

PURPOSE

To discuss the potential implications of obesity for drug administration and absorption from subcutaneous (SC) and intramuscular (IM) injection sites.

SUMMARY

The SC and IM routes are useful for the parenteral administration of medications to optimize pharmacokinetic properties such as time to onset and duration of effect, for cost considerations, or for ease of administration, such as when intravenous access is unavailable. The choice of SC or IM injection depends on the specific medication, with SC administration preferred for products such as insulin where a slower and more sustained response is desirable, while IM administration is usually preferred for products such as vaccines where more rapid absorption leads to a more rapid antibody response. Obesity has the potential to influence the rate and extent of absorption, as well as adverse effects, of medications administered by the SC or IM route through changes in SC tissue composition and depth or by inadvertent administration of IM medications into SC tissue because of improper needle length. Potential adverse effects associated with IM or SC injections in addition to pain, bruising, and hematoma formation include sciatic nerve injury, particularly with IM injection in the upper outer quadrant of the buttock; bone contusion or rarely osteonecrosis if the IM injection is excessively deep; and granulomas, fat necrosis, and calcification with SC injection.

CONCLUSION

Issues related to medication absorption in obese patients are likely to become more prominent in the future with increasing approvals of a wide range of biotherapeutic agents administered by SC injection. Studies should be directed toward these and other agents to assist with dosing decisions in this challenging population.