Systematic review of drug bioavailability following gastrointestinal surgery

Enhancing drug therapy in ostomy patients: Best practice recommendations for medication management

BACKGROUND

Ostomy surgery is a common procedure that poses various challenges for patients and healthcare professionals. There are numerous guidelines addressing different ostomy-related problems (ORPs) and supporting an interdisciplinary approach for ostomy care, but evidence-based literature for optimizing drug therapy after ostomy surgery is lacking.

AIM

To investigate and characterize typical ORPs in relation to drug therapy and provide best practice recommendations from a pharmaceutical point of view.

METHODS

Patients with an ileo- or colostomy were consecutively enrolled in a prospective, interventional monocentric cohort study during hospitalization, with particular attention to medication. A clinical pharmacist assessed DRPs by performing level 3 medication reviews and patient interviews. Pharmacists' interventions (PIs) were evaluated by two senior clinical pharmacists and documented in DokuPIK (Documentation of Pharmacists' Interventions in the Hospital). Following interdisciplinary discussions, physicians either accepted or rejected the proposed changes in drug therapy. Comparisons were made between ileostomy and colostomy patients regarding type and extent of PIs.

RESULTS

Out of the 80 patients included in the cohort, 54 (67.5%) had an ileostomy and 26 (32.5%) a colostomy. In this study, 288 PIs were documented (234 ileostomy vs. 54 colostomy), of wich 94.0% were accepted and implemented by the physicians. The most common reason for PIs in both subgroups (29.6% ileostomy vs. 26.1% colostomy) was a missing drug although indicated (e.g. no loperamide, but high stoma output). The proportion of PIs associated with the ostomy was higher in ileostomy patients (48.3% ileostomy vs. 31.5% colostomy; p = 0.025). Typical ORPs were extracted and analyzed as case studies including recommendations for their respective management and prevention.

CONCLUSION

This study highlights the importance of clinical pharmacists being a part of interdisciplinary teams to collaboratively improve ostomy care and patient safety. Especially ileostomy patients are more vulnerable for ORPs in the context of drug therapy and need to be monitored carefully.

Bioavailability of Orally Administered Drugs After Bariatric Surgery

PURPOSE OF REVIEW

Oral drug absorption after bariatric surgery is likely to be altered, but the impact of different bariatric surgery procedures on individual drugs is not uniform. The aim of this article is to describe factors influencing the bioavailability of orally administered drugs after bariatric surgery and to provide readers with practical recommendations for drug dosing. We also discuss the medications that may be harmful after bariatric surgery.

RECENT FINDINGS

The fundamental factors for enteral drug absorption are the production of gastric acid; the preserved length of the intestine, i.e., the size of the absorption surface and/or the preserved enterohepatic circulation; and the length of common loop where food and drugs are mixed with digestive enzymes and bile acids. Bypassing of metabolizing enzymes or efflux pumps and changes in intestinal motility can also play an important role. Significant changes of drug absorption early after the anatomic alteration may also be gradually ameliorated due to gradual intestinal adaptation. The most affected drugs are those with low or variable bioavailability and those undergoing enterohepatic circulation. Attention should also be paid to oral drug formulations, especially in the early postoperative period, when immediate-release and liquid formulations are preferred. The changes in oral bioavailability are especially clinically meaningful in patients treated with drugs possessing narrow therapeutic index (e.g., oral anticoagulants, levothyroxine, and anticonvulsants) or in acute conditions (e.g., anti-infectives); nevertheless, it may also influence the therapeutic value of chronic therapy (e.g., antidepressants. antihypertensives, antiplatelets, statins, PPIs, contraceptives, and analgesics); therapeutic effect of chronic therapy is further influenced by pharmacokinetic alterations resulting from weight loss. Therapeutic drug monitoring, periodical clinical evaluation, and adequate dose adjustments are necessary. Due to safety reasons, patients should avoid oral bisphosphonates, regular use of non-steroidal anti-inflammatory drugs, and, if possible, corticosteroids after bariatric surgery.

Medication use in a cohort of adults with chronic intestinal failure: A prospective cross-sectional study

BACKGROUND

Oral drug therapy may be compromised in chronic intestinal failure (IF) because of alterations in absorption and transit. Only scarce literature is available on which medication patients with chronic IF take in daily life. The aim was to describe the medication use in these patients.

METHODS

A medication history was obtained from adults with chronic IF treated in our tertiary care IF center. Degree of polypharmacy, drug classes, Biopharmaceutics Classification System classes, route of administration, and formulation of drugs were analyzed.

RESULTS

From October 2019 until December 2020, 72 patients (35 patients with short bowel syndrome [SBS] and 37 patients without SBS) were included. Polypharmacy was seen in 85.7% of patients with SBS and 75.7% of patients without SBS. The top three drug classes were proton-pump inhibitors, vitamin D or acetaminophen, and antimotility medication or laxatives/benzodiazepines. Approximately 25% of the drugs were classified as Biopharmaceutics Classification System class I drugs. In patients with SBS (78%) and patients without SBS (74.9%), most medication was taken orally, requiring gastrointestinal absorption of the active substance to be pharmacologically active. Most of these medications (77% in patients with SBS and 80.8% in patients without SBS) were formulated as a capsule or tablet, requiring disintegration and dissolution in the gastrointestinal tract before absorption can take place.

CONCLUSION

Polypharmacy was observed in most patients with chronic IF. Most medication was taken orally in formulations requiring disintegration, dissolution, and gastrointestinal absorption, which could be compromised in chronic IF.

Long-term weight loss outcomes after bariatric surgery: a propensity score study among patients with psychiatric disorders

INTRODUCTION

To analyze the safety and long-term result of bariatric surgery in patients with psychiatric disorders.

MATERIAL AND METHODS

From January 2009 to December 2018, n = 961 patients underwent bariatric surgery in a tertiary center. Among them, two groups of patients were created: a group of patients with psychiatric disorders (PG) and a group without psychiatric disorders (CG), using a propensity score matched (PSM). Primary endpoint was long-term outcomes and secondary endpoints were the postoperative morbidity 90 days after surgery, late morbidity, occurrence of psychiatric adverse events, and resolution of obesity-related comorbidities.

RESULTS

Analysis with PSM permitted to compare 136 patients in each group, with a ratio 1:1. TWL% at 2 years in the PG was 32.7% versus 36.6% in the CG (p = 0.002). Overall surgical morbidity was higher in the PG than the CG (28% vs 17%, p = 0.01). Severe surgical complications were not statistically significant (4% vs 3%, p = 0.44). Psychiatric adverse events were significantly more frequent in the PG than in the CG. The resolution of obesity comorbidities was equivalent for both groups at 2 years.

CONCLUSION

Substantial weigh loss was reported among patients with psychiatric disorders receiving bariatric surgery at the cost of more non-severe surgical complications. Further, a psychiatric postoperative follow-up visit may be warranted for patients with preoperative psychiatric disorders, given the incidence of psychiatric adverse events.

Psychotropic Medications in Metabolic and Bariatric Surgery: Research Updates and Clinical Considerations

PURPOSE OF REVIEW

We review evidence for assessing and monitoring psychotropic medications in metabolic and bariatric surgery (MBS) patients. We describe weight gain side effects, potential perioperative risks, pharmacokinetic changes that occur after MBS, and conclude with clinical recommendations.

RECENT FINDINGS

Research on psychiatric medication use and post-MBS weight outcomes is lacking and inconsistent; however, there is consistent evidence that, though variable, psychiatric medication use is associated with weight gain. Several meta-analyses and reviews provide guidance on lowering risk when appropriate. Perioperative lithium toxicity and SSRI discontinuation syndrome also warrant consideration, as do potential post-operative pharmacokinetic changes. In the absence of data for each psychiatric drug classification, close symptom monitoring and, where appropriate, serum concentration monitoring are recommended. MBS patients are a psychiatrically vulnerable population, and many are on psychiatric medications. Given potential weight/metabolic side effects, perioperative complications, and post-operative pharmacokinetic changes that occur with psychotropic medication use, providers should stay well informed on psychiatric medication management considerations.

Impaired Absorption of Extended-Release Potassium Chloride in a Patient With a High-Output Ileostomy

BACKGROUND

Best practices in the management of ileostomies include use of immediate release (IR) medications and elimination of enteric coated and prokinetic agents. Extended-release (ER) potassium chloride is designed for postpyloric release rather than colonic absorption and is postulated to be an appropriate option for potassium repletion in this patient subset.

CASE

We present a patient with an ileostomy who received intravenous ER and IR oral potassium chloride supplementation following diverting loop ileostomy. Clinical responsiveness to ER potassium chloride was poor; 15 to 40 mEq was required to replace 0.1 mEq/L of potassium. However, upon transition to IR potassium chloride, only 6.67 mEq was required to replace 0.1 mEq/L of potassium.

CONCLUSIONS

Our experience in this case suggests that patients with surgical alterations to their gastrointestinal tracts who fail to have expected rises in serum potassium levels may benefit from early conversion to IR potassium chloride.

Oral absorption of oxycodone in patients with short bowel syndrome

BACKGROUND

Short bowel syndrome is a disorder with several complications such as malnutrition and failure of drug therapy. Treatment with opioids is needed in many patients, and oral medication is preferred. However, optimal dosing is a difficult task as current guidelines are based on an intact gastrointestinal tract. Hence, the aim of this explorative case study was to assess the pharmacokinetics of orally administered oxycodone in patients with short bowel syndrome.

METHODS

Six patients with short bowel syndrome were administered 10 mg oral solution oxycodone after an overnight fast. Oxycodone plasma concentrations were determined over a 6-hour period. Pharmacokinetic profiles were visually inspected. Pharmacokinetic parameters: maximum plasma concentration, time of maximum concentration and area under the curve were calculated. Data were also compared to mean values obtained in healthy participants.

RESULTS

A clinically relevant concentration of oxycodone was found in all patients, although with large inter-individual variation. The absorption fraction tended to correlate positively with total intestinal length. Additionally, preservation of some or the entire colon seemed further to increase the absorption fraction. Time of maximum concentration varied from 30 min to approximately 90 min.

CONCLUSIONS

Oxycodone is absorbed in a clinically relevant extent in patients with short bowel syndrome, but bioavailability varies greatly between patients, which shall be taken into consideration. Absorption is related to functional small intestinal length, but preservation of colon is also beneficial. Still, optimal therapeutic dosing must be individualized, and other factors such as those related to malnutrition and motility shall also be taken into consideration.

Current challenges and future perspectives in oral absorption research: An opinion of the UNGAP network

Although oral drug delivery is the preferred administration route and has been used for centuries, modern drug discovery and development pipelines challenge conventional formulation approaches and highlight the insufficient mechanistic understanding of processes critical to oral drug absorption. This review presents the opinion of UNGAP scientists on four key themes across the oral absorption landscape: (1) specific patient populations, (2) regional differences in the gastrointestinal tract, (3) advanced formulations and (4) food-drug interactions. The differences of oral absorption in pediatric and geriatric populations, the specific issues in colonic absorption, the formulation approaches for poorly water-soluble (small molecules) and poorly permeable (peptides, RNA etc.) drugs, as well as the vast realm of food effects, are some of the topics discussed in detail. The identified controversies and gaps in the current understanding of gastrointestinal absorption-related processes are used to create a roadmap for the future of oral drug absorption research.

Impact of gastrointestinal tract variability on oral drug absorption and pharmacokinetics: An UNGAP review

The absorption of oral drugs is frequently plagued by significant variability with potentially serious therapeutic consequences. The source of variability can be traced back to interindividual variability in physiology, differences in special populations (age- and disease-dependent), drug and formulation properties, or food-drug interactions. Clinical evidence for the impact of some of these factors on drug pharmacokinetic variability is mounting: e.g. gastric pH and emptying time, small intestinal fluid properties, differences in pediatrics and the elderly, and surgical changes in gastrointestinal anatomy. However, the link of colonic factors variability (transit time, fluid composition, microbiome), sex differences (male vs. female) and gut-related diseases (chronic constipation, anorexia and cachexia) to drug absorption variability has not been firmly established yet. At the same time, a way to decrease oral drug pharmacokinetic variability is provided by the pharmaceutical industry: clinical evidence suggests that formulation approaches employed during drug development can decrease the variability in oral exposure. This review outlines the main drivers of oral drug exposure variability and potential approaches to overcome them, while highlighting existing knowledge gaps and guiding future studies in this area.

Impact of gastrointestinal physiology on drug absorption in special populations--An UNGAP review

The release and absorption profile of an oral medication is influenced by the physicochemical properties of the drug and its formulation, as well as by the anatomy and physiology of the gastrointestinal (GI) tract. During drug development the bioavailability of a new drug is typically assessed in early clinical studies in a healthy adult population. However, many disease conditions are associated with an alteration of the anatomy and/or physiology of the GI tract. The same holds true for some subpopulations, such as paediatric or elderly patients, or populations with different ethnicity. The variation in GI tract conditions compared to healthy adults can directly affect the kinetics of drug absorption, and thus, safety and efficacy of an oral medication. This review provides an overview of GI tract properties in special populations compared to healthy adults and discusses how drug absorption is affected by these conditions. Particular focus is directed towards non-disease dependent conditions (age, sex, ethnicity, genetic factors, obesity, pregnancy), GI diseases (ulcerative colitis and Crohn's disease, celiac disease, cancer in the GI tract, Roux-en-Y gastric bypass, lactose intolerance, Helicobacter pylori infection, and infectious diseases of the GI tract), as well as systemic diseases that change the GI tract conditions (cystic fibrosis, diabetes, Parkinson's disease, HIV enteropathy, and critical illness). The current knowledge about GI conditions in special populations and their impact on drug absorption is still limited. Further research is required to improve confidence in pharmacokinetic predictions and dosing recommendations in the targeted patient population, and thus to ensure safe and effective drug therapies.

Roux-en-Y Gastric Bypass and Antipsychotic Therapeutic Drug Monitoring: Two Cases

Many patients with psychiatric conditions undergo bariatric surgery. The Roux-en-Y gastric bypass (RYGB) procedure alters medication pharmacokinetic properties and may have significant impact on drug response. Our report is the first to describe atypical antipsychotic therapeutic drug monitoring in patients who have undergone RYGB. The first patient is a 53-year-old female with a stable psychiatric condition undergoing a laparoscopic RYGB. Her medications prior and following the procedure include bupropion, fluvoxamine, lurasidone, methylphenidate, oxcarbazepine, and verapamil. A concentration steady-state lurasidone concentration obtained prior to the procedure was 20 ng/mL and returned at 8.1 ng/mL, 29 days after surgery. The second patient is a 42-year-old female psychiatric inpatient who had previously undergone an RYGB procedure. Medications on admission included phenytoin, oxcarbazepine, risperidone, and venlafaxine. The patient was believed to be a good candidate for a long-acting antipsychotic and paliperidone was chosen. After concentration-steady-state on 6 mg oral paliperidone, a 23.5-hour trough level was drawn. The patient was noted to be improved on the oral paliperidone, the paliperidone long-acting injection was given, and the patient was discharged. After discharge, the paliperidone concentration returned very low at 1.1 ng/mL. We describe the contributions of drug-drug interactions, medication release mechanisms, and food coadministration that may have affected our therapeutic drug monitoring. Our therapeutic drug monitoring results need to be replicated prior to use in the general population but suggest that oral extended-release drug formulations are particularly poor choices and that nonoral antipsychotic formulations may be preferred in some patients who have undergone RYBG.