Drug-induced bowel complications and toxicities: imaging findings and pearls

The use of diverse types of drugs can result in a variety of acute and chronic complications that affect almost any organ. The bowel is one of the organs impacted by the side effects of medications. Imaging frequently plays a crucial role in the detection and characterization of complications occurring in the bowel. They include pseudomembranous colitis or antibiotic-associated colitis; angioedema induced by angiotensin-converting enzyme inhibitors; nonsteroidal anti-inflammatory drug-induced enteropathy; cocaine toxicity; clozapine-induced hypomobility; and bowel toxicity induced by chemotherapeutic agents. It is imperative that radiologists are fully aware of these complications and toxicities as well as the relevant findings. In this way, proper treatment can be implemented immediately. The treatment will involve discontinuation of a drug or a change in regimen.

Imaging of the chemotherapy-induced hepatic damage: Yellow liver, blue liver, and pseudocirrhosis

The liver is the major drug-metabolizing and drug-detoxifying organ. Many drugs can cause liver damage through various mechanisms; however, the liver response to injury includes a relatively narrow spectrum of alterations that, regardless of the cause, are represented by phlogosis, oxidative stress and necrosis. The combination of these alterations mainly results in three radiological findings: vascular alterations, structural changes and metabolic function reduction. Chemotherapy has changed in recent decades in terms of the drugs, protocols and duration, allowing patients a longer life expectancy. As a consequence, we are currently observing an increase in chemotherapy-associated liver injury patterns once considered unusual. Recognizing this form of damage in an early stage is crucial for reconsidering the therapy regimen and thus avoiding severe complications. In this frontier article, we analyze the role of imaging in detecting some of these pathological patterns, such as pseudocirrhosis, “yellow liver” due to chemotherapy-associated steatosis-steatohepatitis, and “blue liver”, including sinusoidal obstruction syndrome, veno-occlusive disease and peliosis.

Chebulinic acid is a safe and effective antiangiogenic agent in collagen-induced arthritis in mice

BACKGROUND

Although vascular endothelial growth factor-A (VEGF)-induced angiogenesis has been reported to play an important role in the pathogenesis of rheumatoid arthritis (RA), serious side effects, mainly grade 2-3 hypertension, which is commonly observed with currently available anti-VEGF agents, can be detrimental for RA patients due to hypertension and associated cardiovascular complications seen in these patients. Thus, identification of anti-VEGF molecules that do not increase blood pressure could be useful for the treatment of RA. Chebulinic acid (CI), a water-soluble small-molecule tannin, can inhibit the actions of VEGF, and a report suggested that CI might not increase blood pressure due to its compensatory effects on the cardiovascular system. Therefore, the effects of CI on blood pressure in mice and the progression of the disease in a murine collagen-induced arthritis (CIA) model were investigated.

METHODS

CIA was induced in DBA/1J mice with type II collagen. The effects of CI in these animals were then evaluated by determination of clinical, histopathological, and immunohistochemical parameters. The effects of CI on VEGF-induced proangiogenic genes and signaling pathways were examined in vitro and in vivo.

RESULTS

Significant CD31 and VEGF expressions were detected in the synovial tissues of mice with CIA, similar to their expressions observed in human RA patients. However, treatment with CI significantly inhibited paw swelling, decreased the mean articular index and joint pathology scores in these animals through inhibition of VEGF-induced proangiogenic gene expressions and signaling pathways that regulate angiogenesis. Unlike currently used antiangiogenic agents, CI at a dose that inhibits VEGF actions did not increase blood pressure in mice.

CONCLUSION

CI can act as a safe and potent anti-VEGF antiangiogenic agent for the treatment of types of inflammatory arthritis, such as RA.

A Review of the Mechanisms and Clinical Implications of Precision Cancer Therapy-Related Toxicity: A Primer for the Radiologist

OBJECTIVE. The purpose of this review is to elucidate the mechanisms, types, and clinical significance of molecular targeted therapy (MTT) and immune checkpoint inhibitors (ICIs) and their related toxicity, emphasizing the radiologic manifestations. CONCLUSION. The related toxicities of MTT and ICIs can have acute, recurrent, chronic, and delayed presentations. These toxicities may serve as markers of response and survival. By understanding the clinical significance of drug toxicities, radiologists can play an important role in personalized cancer therapy.

A review of the imaging manifestations of immune check point inhibitor toxicities

The past decade has witnessed a paradigm shift in cancer therapy owing to the introduction of immune checkpoint inhibitors (ICIs) and it is now commonplace for radiologists to image patients on therapy with these agents. The purpose of this review is to detail the mechanism, radiological manifestations and clinical significance of ICI related toxicities, according to the organ system involved. ICI related toxicities that have known imaging manifestations include colitis, enterocolitis, pancreatitis, hepatitis, endocrine toxicities, pneumonitis, cardiovascular toxicity and musculoskeletal toxicity. These toxicities may be acute, recurrent or chronic in nature. Radiologists must be aware of the imaging features and clinical significance of these toxicities in order to effectively participate in personalized cancer therapy.

Overview of imaging findings associated with systemic therapies in advanced epithelial ovarian cancer

PURPOSE

To provide an overview for radiologists of the systemic agents used in the treatment of advanced epithelial ovarian cancer (EOC) and their associated toxicities.

RESULTS

EOC is a common gynecological malignancy, with the majority of patients presenting with advanced stage disease at the time of diagnosis. Although primary cytoreductive surgery and chemotherapy are the principal treatments for EOC, recurrence rates of disease remain high. As several molecular targeted therapies have been developed in the last decade, various novel agents have shown efficacy in the treatment of advanced EOC. Advanced EOC will be discussed by outlining the relevant radiological features of toxicities.

CONCLUSION

Knowledge of the systemic therapies utilized in the treatment of advanced EOC and their associated radiological features is critical in diagnostic image interpretation.

Symptomatic Biliary Disorders During Lenvatinib Treatment for Thyroid Cancer: An Underestimated Problem

Background: The prognosis of several human malignancies has dramatically improved after the introduction of tyrosine kinase inhibitors (TKIs); however, their use has been associated with a large spectrum of adverse events, including symptomatic biliary disorders. In the phase III trial of lenvatinib in radioactive iodine (RAI)-refractory differentiated thyroid cancer (DTC) patients, gallbladder (GB) and biliary duct (BD) diseases and complications were reported. We evaluated symptomatic biliary disorders during treatment with lenvatinib in real-life practice to provide a more exhaustive understanding of its toxicity. Methods: We retrospectively evaluated all consecutive patients treated with lenvatinib in our center for progressive RAI-refractory DTC, excluding those who underwent cholecystectomy before the start of therapy. We report all radiologically confirmed symptomatic GB/BD disorders, which were subsequently treated with cholecystectomy, and we describe their management along with relevant biochemical and histological findings. All available GB/BD imaging of patients who developed biliary toxicity during lenvatinib was reviewed by a single experienced radiologist, including computed tomography scans performed for tumor assessment at baseline and during TKI therapy. Results: Five patients (14.7%) developed symptomatic radiologically confirmed biliary disease after a median time of 4.4 months of lenvatinib treatment [interquartile range 3.4-14.4 months] and thus underwent cholecystectomy. A scheduled surgical approach was possible only in two cases; in the remaining patients, presurgical TKI interruption was shorter than one week. After wound healing, treatment was resumed by all subjects. Three patients showed mild biochemical alterations in the two previous monthly follow-up visits. Before the start of treatment, GB/BD abnormalities were radiologically detected only in one case. Conclusions: In our cohort, an unexpectedly high proportion of RAI-refractory DTC patients treated with lenvatinib developed a symptomatic biliary disorder with the need of surgical intervention. Further studies are required to optimize the diagnosis and treatment of patients at higher risk of developing a symptomatic GB/BD disease during assumption of lenvatinib.

Overview of systemic treatment in recurrent and advanced cervical cancer: a primer for radiologists

Imaging has a central role in surveillance of cervical cancer, guiding decision on when to initiate treatment for recurrent disease and to guide management in advanced cervical cancer. Due to the increased availability of pelvic radiation therapy, the rate of atypical presentation of recurrent disease has increased. Simultaneously, the array of systemic therapies now available for advanced cervical cancer has considerably expanded in the last few years, with therapies now available in mid and low-income countries. While pelvic recurrences are amenable of loco-regional treatment, recurrent disease may present with metastases to the thoracoabdominal organs, lymph nodes, bones, skin and brain, for which systemic treatment represent the standard of care. Besides combined chemotherapy regimens, alternative chemotherapies, biosimilars and immune checkpoint inhibitors are now available, each associated with a definite pattern of response and toxicity. In this review, after describing the typical and atypical presentations of recurrent and advanced cervical carcinoma on cross-sectional imaging, we will discuss systemic treatment for recurrent or advanced disease and their associated radiographic sequelae, in light of the newly available therapies.

Hallmarks of Cancer in the Reading Room: A Guide for Radiologists

OBJECTIVE

The hallmarks of cancer are mechanisms that cells develop to undergo malignant transformation. The targeting of these hallmarks by newer cancer therapies results in new mechanisms of response, toxicity, and resistance. The purpose of this article is to review these hallmarks, their associated targeted therapies, imaging features of responses, and toxicities.

CONCLUSION

Ten hallmarks, among them proliferative signaling, angiogenesis, immune response, and genome instability, are reviewed. Molecular targeted therapies, including antiangiogenic factors and immune checkpoint inhibitors, target these hallmarks.

Unintended Consequences of Systemic and Ablative Oncologic Therapy in the Abdomen and Pelvis

Human cancers are genetically complex and diverse. Although advances in oncologic therapy aim to define and target unique steps in carcinogenesis, oncologists often rely on less discriminate anticancer therapies that have consequences for normal tissues. Even many of the so-called targeted therapies currently employed can adversely affect normal cells, leading to complications that necessitate dose reductions or cessation of specific therapies. This article explores the unintended consequences of currently employed systemic and ablative anticancer therapies that might manifest at imaging examinations of the abdomen and pelvis, including cytotoxic, molecular targeted, and immunologic agents; ablation; and hematopoietic stem cell transplant. Each of these treatments can have both major and minor unintended effects in the targeted organ(s), in local or adjacent structures, or at distant sites. Timely detection and reporting of adverse consequences of anticancer therapies by the astute imager can result in critical treatment modifications and/or lifesaving interventions; therefore, knowledge of these unintended effects is paramount for radiologists interpreting the results of imaging examinations in cancer patients. ^©RSNA, 2018.

Biliary and pancreatic complications of molecular targeted therapies in cancer imaging

The purpose of this review is to familiarize radiologists with the different imaging manifestations of biliary and pancreatic toxicity of molecular targeted therapies. The advent of molecular targeted therapies for cancer treatment has prompted radiologists to be familiar with these new molecules, their patterns of response, and their class-specific toxicities. While liver and bowel toxicities have been extensively reported in literature, less is known about the pathogenesis and imaging of toxicity involving the pancreatobiliary system. Biliary and pancreatic toxicity of molecular targeted therapies present with variable manifestations and varying degrees of severity, from asymptomatic liver function tests elevation to acute pancreatitis or cholecystitis. Management of these conditions depends on the clinical scenario and the severity of the findings. In this article, we will (1) present the various classes of molecular targeted therapies most commonly associated with biliary and pancreatic toxicity; (2) illustrate imaging findings of drug-associated biliary and pancreatic injuries and their possible differential diagnosis; and (3) provide a guide for management of these conditions.

Imaging of hepatic toxicity of systemic therapy in a tertiary cancer centre: chemotherapy, haematopoietic stem cell transplantation, molecular targeted therapies, and immune checkpoint inhibitors

The purpose of this review is to familiarise radiologists with the spectrum of hepatic toxicity seen in the oncology setting, in view of the different systemic therapies used in cancer patients. Drug-induced liver injury can manifest in various forms, and anti-neoplastic agents are associated with different types of hepatotoxicity. Although chemotherapy-induced liver injury can present as hepatitis, steatosis, sinusoidal obstruction syndrome, and chronic parenchymal damages, molecular targeted therapy-associated liver toxicity ranges from mild liver function test elevation to fulminant life-threatening acute liver failure. The recent arrival of immune checkpoint inhibitors in oncology has introduced a new range of immune-related adverse events, with differing mechanisms of liver toxicity and varied imaging presentation of liver injury. High-dose chemotherapy regimens for haematopoietic stem cell transplantation are associated with sinusoidal obstruction syndrome. Management of hepatic toxicity depends on the clinical scenario, the drug in use, and the severity of the findings. In this article, we will (1) present the most common types of oncological drugs associated with hepatic toxicity and associated liver injuries; (2) illustrate imaging findings of hepatic toxicities and the possible differential diagnosis; and (3) provide a guide for management of these conditions.

Molecular Targeted Therapy in Modern Oncology: Imaging Assessment of Treatment Response and Toxicities

Oncology is a rapidly evolving field with a shift toward personalized cancer treatment. The use of therapies targeted to the molecular features of individual tumors and the tumor microenvironment has become much more common. In this review, anti-angiogenic and other molecular targeted therapies are discussed, with a focus on typical and atypical response patterns and imaging manifestations of drug toxicities.

Multimodality imaging of locally recurrent and metastatic cervical cancer: emphasis on histology, prognosis, and management

The management of recurrent and metastatic cervical cancer is evolving in concert with the available advanced imaging techniques and molecular targeted therapy. The purpose of this review is to provide an overview of imaging and treatment of cervical cancer patients with locoregional recurrence and metastatic disease, with emphasis on characteristic patterns of spread based on histology (squamous cell carcinoma and other subtypes), prognostic factors, diagnosis, and treatment response assessment, as well as updated therapeutic options.

Pazopanib-Induced Severe Acute Pancreatitis

Pazopanib is an oral angiogenesis inhibitor targeting vascular endothelial growth factor receptors, platelet-derived growth factor receptors, and c-Kit approved for the treatment of renal cell carcinoma and soft tissue sarcoma. Nonselective kinase inhibitors, such as sunitinib and sorafenib, are known to be associated with acute pancreatitis. There are few case reports of severe acute pancreatitis induced by pazopanib treatment. We present a case of severe acute pancreatitis caused by pazopanib treatment for cutaneous angiosarcoma. The patient was an 82-year-old female diagnosed with cutaneous angiosarcoma. She had been refractory to docetaxel treatment and began pazopanib therapy. Three months after pazopanib treatment, CT imaging of the abdomen showed the swelling of the pancreas and surrounding soft tissue inflammation without abdominal pain. After she continued pazopanib treatment for 2 months, she presented with nausea and appetite loss. Abdominal CT showed the worsening of the surrounding soft tissue inflammation of the pancreas. Serum amylase and lipase levels were 296 and 177 IU/l, respectively. She was diagnosed with acute pancreatitis induced by pazopanib treatment and was managed conservatively with discontinuation of pazopanib, but the symptoms did not improve. Subsequently, an abdominal CT scan demonstrated the appearance of a pancreatic pseudocyst. She underwent endoscopic ultrasound-guided pseudocyst drainage using a flared-end fully covered self-expandable metallic stent. Then, the symptoms resolved without recurrence. Due to the remarkable progress of molecular targeted therapy, the oncologist should know that acute pancreatitis was recognized as a potential adverse event of pazopanib treatment and could proceed to severe acute pancreatitis.

Assessment and management of gastrointestinal toxicities and lab abnormalities related to targeted therapy

OBJECTIVES

To identify the most common gastrointestinal toxicities and laboratory abnormalities associated with targeted therapies, as well as the assessment and management necessary to minimize adverse events related to these side effects.

DATA SOURCES

Peer-reviewed articles and national guidelines for oncology practice.

CONCLUSION

Common toxicities of diarrhea, mucositis, and laboratory abnormalities are often associated with the use of targeted agents and require skilled assessment and early management interventions to prevent severe complications or treatment interruption.

IMPLICATIONS FOR NURSING PRACTICE

Emerging trends focused on targeted therapy increase the importance of the oncology nurse's role in assessment, education, and evidenced-based recommendations to meet patient needs.

Motesanib with or without panitumumab plus FOLFIRI or FOLFOX for the treatment of metastatic colorectal cancer

PURPOSE

This study assessed the safety, efficacy, and pharmacokinetics of motesanib, a multitargeted small molecule angiogenesis inhibitor, with and without panitumumab, in combination with FOLFIRI or FOLFOX in patients with metastatic colorectal cancer (mCRC).

METHODS

This open-label, phase 1b, two-part, multicenter study in patients with mCRC and ≤1 prior treatment evaluated escalating doses (50, 75, 100, or 125 mg QD, 75 mg BID) of motesanib with panitumumab and chemotherapy (Part 1) and the target dose of motesanib with chemotherapy (Part 2).

RESULTS

At 17 sites in the USA and Australia, 119 patients were enrolled between December 2004 and February 2010. In Part 1 [motesanib plus panitumumab/FOLFIRI (n = 36) or plus panitumumab/FOLFOX (n = 17)], all motesanib doses tested were tolerated and 125 mg QD was deemed the target dose. Following toxicity results for combination therapy in other trials, panitumumab was withdrawn from the study. Part 2 evaluated motesanib 125 mg with chemotherapy [FOLFIRI (n = 37); FOLFOX (n = 29)]. The primary endpoint, objective response rate in patients with measurable disease by RECIST, was 20 % overall and was higher among patients receiving first-line (27 % overall; FOLFOX, 24 %; FOLFIRI, 27 %) compared with second-line therapy (14 % overall; FOLFOX, 0 %; FOLFIRI, 20 %). The most common adverse events were diarrhea, nausea, fatigue, and hypertension. We observed a low rate of cholecystitis [3 of 119 (2.5 %)], a known adverse event of motesanib and other small molecule VEGF inhibitors.

CONCLUSIONS

Motesanib 125 mg QD in combination with FOLFIRI or FOLFOX chemotherapy was tolerated and demonstrated modest efficacy in first-/second-line mCRC.

Dopamine is a safe antiangiogenic drug which can also prevent 5-fluorouracil induced neutropenia

The role of vascular endothelial growth factor A (VEGFA) in tumor angiogenesis is well established and accordingly, molecules targeting VEGFA or its receptors are being presently used in the clinics for treatment of several types of cancer. However, these antiangiogenic agents are expensive and have serious side effects. Thus identification of newer drugs with manageable systemic side effects or toxicities is of immense clinical importance. Since we have reported earlier that dopamine (DA) inhibits VEGFA induced angiogenesis in experimental tumor models, we therefore sought to investigate whether DA treatment results in similar toxicities like other antiangiogenic agents. Our results indicated that unlike sunitinib, another commonly used antiangiogenic agent in the clinics which targets VEGF receptors, DA [50 mg/kg/days × 7days intraperitoneally (i.p.)] not only could inhibit tumor angiogenesis and growth of HT29 human colon cancer and LLC (Lewis lung carcinoma) in mice, it also did not cause hypertension, hematological, renal and hepatic toxicities in normal, HT29 and LLC tumor bearing animals. Furthermore and interestingly, in contrast to the currently used antiangiogenic agents, DA also prevented 5-fluorouracil (5FU) induced neutropenia in HT29 colon cancer bearing mice. This action of DA was through inhibition of 5FU mediated suppression of colony forming unit-granulocyte macrophage colony forming units in the bone marrow. Thus our results indicate that DA may be safely used as an antiangiogenic drug for the treatment of malignant tumors.

Update on the role of imaging in management of metastatic colorectal cancer

Evolution in the treatment of metastatic colorectal cancer (mCRC) has led to significant improvement in the survival of these patients. Surgery is useful in patients with resectable disease. Liver-directed therapies such as hepatic arterial infusion, transarterial radio- and chemoembolization, and percutaneous ablation are sometimes used by oncologists when the liver is the only site of metastatic disease. Unresectable mCRC is typically treated with systemic chemotherapy. First-line systemic chemotherapeutic regimens for mCRC are FOLFOX (combination of 5-fluorouracil/leucovorin [5-FU/LV] and oxaliplatin) and FOLFIRI (combination of 5-FU/LV and irinotecan) combined with molecular targeted drugs. Molecular targeted therapies that are effective in treating mCRC include antiangiogenic agents such as bevacizumab-an antibody against vascular endothelial growth factor-and antibodies directed against epidermal growth factor receptor (EGFR). EGFR-directed antibodies such as cetuximab and panitumumab have been shown to produce activity only in wild-type KRAS tumors. Imaging modalities such as multidetector computed tomography (CT), magnetic resonance imaging, and positron emission tomography/CT play a major role in the selection of appropriate treatment strategies. Assessment of treatment response in patients who undergo liver-directed and systemic therapy requires imaging at regular intervals. Recent studies have shown that alternative treatment response criteria may be more predictive of pathologic response in mCRC than conventional criteria such as Response Evaluation Criteria in Solid Tumors. Awareness of unusual response patterns, as well as of complications and toxicities, is helpful in guiding patient management.

Clinical problem solving: utility of sonography in oncologic patients

This review demonstrates the unique advantages of sonography in the oncologic setting. Although computed tomography, magnetic resonance imaging, and positron emission tomography-computed tomography are primary imaging modalities for evaluation of the oncologic patient, sonography is useful for evaluation of various conditions and clinical scenarios associated with cancer. The following article will illustrate the utility of sonography at a tertiary cancer center for diagnosis and problem solving.

Update on the management of gastroenteropancreatic neuroendocrine tumors with emphasis on the role of imaging

OBJECTIVE

The purposes of this article are to review the current management of gastroenteropancreatic neuroendocrine tumors (GEP-NETs) based on the 2012 National Comprehensive Cancer Network guidelines and to describe the role of imaging in a multidisciplinary approach.

CONCLUSION

The management of GEP-NETs has become complex, requiring a multidisciplinary approach. The World Health Organization classification of GEP-NETs has been revised; the U.S. Food and Drug Administration has approved molecular targeted agents (sunitinib, everolimus) for the treatment of pancreatic NETs; and the National Comprehensive Cancer Network clinical practice guidelines have been updated.

Acute pancreatitis associated with molecular targeted therapies: a retrospective review of the clinico-radiological features, management and outcome

PURPOSE

To study the presentation, radiological features, management and outcome of acute pancreatitis detected on imaging in patients receiving molecular targeted therapy (MTT).

MATERIALS AND METHODS

In this IRB-approved, HIPAA-compliant retrospective study, search of the radiology database from January 2005 through September 2012 revealed 91 cancer patients with radiologic evidence of acute pancreatitis. Of these, 15 patients receiving MTT (7 women, 8 men; mean age 59 years, range 25-84 years) and fulfilling the criteria of acute pancreatitis without any confounding factors were included. Imaging at initial diagnosis of pancreatitis and subsequently were reviewed by three radiologists in consensus; clinical presentation, management, and outcome were documented from the medical record.

RESULTS

Eleven patients had focal and four had diffuse pancreatitis. The tail of the pancreas (n = 6) was the most common site of focal pancreatitis. Of the 14/15 patients who underwent CT, modified CT severity index was 2 in 12 patients and 4 in 2 patients. One patient (1/15) who underwent only FDG-PET/CT showed focal pancreatitis. None of the patients had pancreatic necrosis or peripancreatic collections. Findings resolved in all the patients after discontinuation of MTT, except in one patient who died of progressive disease. No radiological or surgical interventions were required in any of the patients. Findings recurred in 4/9 patients (44%) in whom MTT was restarted.

CONCLUSION

MTT-associated pancreatitis is usually mild, focal, and managed conservatively with discontinuation of MTT. The imaging findings are subtle and in our study, pancreatitis recurred in 44% of patients after restarting MTT.

Molecular targeted therapies in non-GIST soft tissue sarcomas: what the radiologist needs to know

Non-gastrointestinal stromal soft tissue sarcomas are uncommon neoplasms that have a dismal prognosis due to a high incidence of metastases and a poor response to conventional chemotherapy. The identification of characteristic genetic alterations in several of these tumors has opened the window for molecular targeted therapies in patients who have failed conventional chemotherapy. Imaging plays a critical role in assessing the response to these novel therapeutic agents. Just like the response of gastrointestinal stromal tumors to imatinib, the response of non-gastrointestinal stromal soft tissue sarcomas to molecular targeted drugs is better evaluated on imaging by alternate tumor response criteria such as the Choi criteria. In addition, these drugs are associated with distinct class-specific drug toxicities that can come to attention for the first time on imaging. The purpose of this article is to provide a primer for the radiologist on the various molecular targeted therapies in advanced/metastatic non-gastrointestinal stromal soft tissue sarcomas with emphasis on the role of imaging in assessing treatment response and complications.

Complications of targeted drug therapies for solid malignancies: manifestations and mechanisms

OBJECTIVE

This article reviews important complications of targeted drug therapies for solid malignancies that can be identified on diagnostic imaging. Wherever possible, known or proposed mechanistic explanations for drug complications are emphasized.

CONCLUSION

Familiarity with the toxicity profiles of different targeted cancer therapies is important for identifying drug-related complications and for differentiating drug effects from disease progression. A mechanistic understanding may be useful for associating individual drugs with their complications and for predicting the complications of emerging agents.