Drug absorption from oral formulations in patients with short bowel syndrome: a comprehensive update of the literature

INTRODUCTION

Drug absorption is often altered and typically diminished in patients with short bowel syndrome (SBS). It is important to understand the patient's gastrointestinal anatomy, the absorptive capacity of the remaining bowel, and the physicochemical and pharmacokinetic properties of the drug to optimize oral pharmacotherapy.

AREAS COVERED

The primary focus was to provide an updated understanding of the absorption of various drugs in patients with short bowel syndrome. Forty-seven studies covering 13 different drug classes were included in the review and study details, patient characteristics, drug characteristics and pharmacokinetic findings were summarized for each drug class.

EXPERT OPINION

Improving and simplifying drug treatment in patients with SBS have high priority, but the patients are multi diseased so knowledge regarding absorption of drugs as e.g. antithrombotic agents, immunosuppressants is urgently needed. Therefore, it is crucial to advance our understanding of the fundamental factors involved in drug absorption, spanning from drug design to pathophysiology. With the growing knowledge in drug design and gastrointestinal pathophysiology, we anticipate the development of computer models that can accurately predict optimal absorption in the future.

Changes of Drug Pharmacokinetics in Patients with Short Bowel Syndrome: A Systematic Review

BACKGROUND AND OBJECTIVES

Short bowel syndrome is a clinical condition defined by malabsorption of nutrients and micronutrients, most commonly following extensive intestinal resection. Due to a loss of absorptive surfaces, the absorption of orally administered drugs is also often affected. The purpose of this study was to systematically review the published literature and examine the effects of short bowel syndrome on drug pharmacokinetics and clinical outcomes.

METHODS

Studies were identified through searches of databases MEDLINE, EMBASE, Web of Science, and SCOPUS, in addition to hand searches of studies' reference lists. Two reviewers independently assessed studies for inclusion, yielding 50 studies involving 37 different drugs in patients with short bowel syndrome.

RESULTS

Evidence of decreased drug absorption was observed in 29 out of 37 drugs, 6 of which lost therapeutic effect, and 14 of which continued to demonstrate clinical benefit through drug monitoring.

CONCLUSIONS

The influence of short bowel syndrome on drug absorption appears to be drug-specific and dependent on the location and extent of resection. The presence of a colon in continuity may also influence drug bioavailability as it can contribute significantly to the absorption of drugs (e.g., metoprolol); likewise, drugs that have a wide absorption window or are known to be absorbed in the colon are least likely to be malabsorbed. Individualized dosing may be necessary to achieve therapeutic efficacy, and therapeutic drug monitoring, where available, should be considered in short bowel syndrome patients, especially for drugs with narrow therapeutic indices.

Combined kidney and intestinal transplantation in patients with enteric hyperoxaluria secondary to short bowel syndrome

Kidney transplantation is the treatment of choice for end-stage renal disease whereas indications for intestinal transplantation are currently restricted to patients with irreversible small bowel failure and severe complications of total parenteral nutrition (mostly shortage and infection of venous accesses, major electrolyte disturbances and liver failure). Enteric hyperoxaluria is secondary to certain intestinal diseases like intestinal resections, chronic inflammatory bowel disease and other malabsorption syndromes and can lead to end-stage renal disease requiring kidney transplantation. We report two patients suffering from renal failure due to enteric hyperoxaluria (secondary to extensive intestinal resection) in whom we elected to replace not only the kidney but also the intestine to prevent recurrence of hyperoxaluria in the transplanted kidney.

Long-term outcome of living related renal transplantation in a patient with short bowel syndrome

Short-bowel syndrome (SBS) is defined as the malabsorptive state that occurs after extensive resection of the small intestine. In patients with SBS, oral administration of drugs usually becomes difficult because of the severity of intestinal failure. We describe a successful living related renal transplantation (LRRTx) in an 18-year-old male with SBS. Shortly after birth, the patient developed necrotizing enterocolitis requiring massive resection of the small intestine, which resulted in SBS. At seven years of age, the patient developed proteinuria and was diagnosed as focal segmental glomerulosclerosis (FSGS). His kidney function was gradually deteriorated toward the end-stage renal failure. The patient received LRRTx at age of 18 years. To evaluate the absorption capacity of the patient, we investigated pharmacokinetics of calcineurine inhibitors (tacrolimus and cyclosporine). The drug concentration, which is sufficient to provide effective immunosuppression, was achieved with cyclosporine, but not with tacrolimus. The patient therefore received a triple immunosuppressive therapy with oral cyclosporine, methyl-prednisolone and mycophenolate mofetil. To prevent both recurrent FSGS and rejection, we repeatedly analyzed the trough level and the pharmacokinetics of cyclosporine after LRRTx. The patient was successfully treated with oral immunosuppression for over 5 years, without hemodialysis. To our knowledge, this is the first report showing the long-term outcome of LRRTx treated with oral cyclosporine in a patient with SBS.

Immunosuppression in infants with short bowel syndrome undergoing isolated liver transplantation

BACKGROUND

Little data exist on immunosuppressive drug absorption in children with short bowel syndrome and intestinal failure associated liver disease (SBS-IFALD).

AIM

To evaluate the absorption of immunosuppressive medications in children with SBS-IFALD undergoing isolated liver transplantation (iLTx).

METHODS

A retrospective review was performed in children with SBS-IFALD undergoing LTx and comparison made with weight, age-matched children undergoing iLTX (extra-hepatic biliary atresia (EHBA) and normal intestinal length and function).

RESULTS

Seven children with SBS-IFALD undergoing iLTx (median residual bowel length, 60 cm, range 40-80) were compared with 15 children undergoing LTx for EHBA. SBS-IFALD children had significantly lower trough tacrolimus levels at three months (5.8 vs. 7.9 ng/mL, p<0.05) and six months (5.0 vs. 8.0 ng/mL, p<0.05), but equivalent levels at 12 months after iLTx. The median calculated dose-normalized concentrations indicated that systemic availability of tacrolimus was comparable in two groups at 3, 6, 12 months (33.1 vs. 23.3; 42.4 vs. 36; 51 vs. 52.9) despite the differences in enteral function. The incidence of acute rejection was 1/7 (SBS-IFALD) and 10/15 (EHBA) group (p = 0.06).

CONCLUSION

Children with SBS-IFALD demonstrated adequate absorption of oral tacrolimus without significant acute rejection rate after iLTx suggesting that modification of immunosuppression is not necessary.