Doxazosin: a newly developed, selective alpha 1-inhibitor in the management of patients with pheochromocytoma

Approach to the Patient: Perioperative Management of the Patient with Pheochromocytoma or Sympathetic Paraganglioma

Pheochromocytomas and sympathetic paraganglioma (PPGL) are rare chromaffin cell tumors originating in the adrenal medulla and sympathetic paraganglia, respectively, which share the capacity to synthesize and release catecholamines. The incidence of PPGL has increased in recent years. Surgical resection is the only curative treatment for PPGL. Management of patients with PPGL is complex and should be done by a specialized multidisciplinary team in centers with broad expertise. Surgical resection of a PPGL is a high-risk procedure for which optimal pretreatment with antihypertensive drugs is required in combination with state-of-the-art surgical procedures and anesthesiological techniques. In this article we discuss the underlying evidence and the pros and cons of presurgical medical preparation. Finally, the areas of uncertainty and controversies in this field are addressed.

The use of doxazosin before adrenalectomy for pheochromocytoma: is the duration related to intraoperative hemodynamics and postoperative complications?

Purpose

No conclusion exists for the optimum duration of preoperative administration of doxazosin (DOX) before adrenalectomy for pheochromocytoma. The purpose of this study is to investigate whether perioperative hemodynamics and postoperative outcomes are related to the duration of DOX administration.

Methods

In total, 132 patients managed preoperatively with single α-receptor blocker DOX were enrolled. All patients underwent adrenalectomy for pheochromocytoma in the Department of Urology, Peking University First Hospital, between January 2001 and July 2019. Patients were divided into three groups based on the duration of preoperative administration of DOX: group A (≤14 days), group B (15–30 days), and group C (>30 days). Patient and tumor characteristics, intraoperative hemodynamics, and postoperative outcomes were recorded and compared.

Results

These patients included 57 men and 75 women, with an average age of 48 years. Clinical characteristics, preoperative hemodynamics, medicine management and surgical approaches were comparable between the three groups. Among the three groups, we found that group C (>30 days) had the lowest intraoperative minimum heart rate [group A vs. group B vs. group C = 60 (52–67) vs. 59 (50–61) vs. 51.5 (50–58.75), p = 0.024] and highest risk of postoperative hypotension requiring vasopressor support [group A vs. group B vs. group C = 14 (20.3%) vs. 12 (27.9%) vs. 10 (50.0%), p = 0.032].

Conclusion

The current study indicated that preoperative management of pheochromocytoma with single α-receptor blocker DOX for more than 30 days after final dose adjustment might lead to intraoperative bradycardia and more postoperative hypotension requiring vasopressor support. Thus, our study does not support long-term (over 30 days) preoperative administration of pheochromocytoma with single α-receptor blocker DOX in the final dose.

An Emergency Department Approach to Drug Treatment of Hypertensive Urgency and Emergency

Patients who present with hypertensive urgency or emergency require immediate attention to assess the severity of illness. Guidelines from the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure are available but do little to address the management of acute elevations in blood pressure. Various treatment options, both old and new, exist to manage these patients in the emergency department. Decisions on therapy are patient specific and depend on the underlying cause of elevated blood pressure. This article sets out to describe specific patient presentations and reviews current available options in the management of hypertensive urgencies and emergencies.

Current perioperative management of pheochromocytomas

Neuroendocrine tumors which have the potential to secrete catecholamines are either associated with sympathetic adrenal (pheochromocytoma) or nonadrenal (paraganglioma) tissue. Surgical removal of these tumors is always indicated to cure and prevent cardiovascular and other organ system complications associated with catecholamine excess. Some of these tumors have malignant potential as well. The diagnosis, localization and anatomical delineation of these tumors involve measurement of catecholamines and their metabolic end products in plasma and urine, ¹²³I-metaiodobenzylguanidine scintigraphy, computed tomography, and/or magnetic resonance imaging. Before surgical removal of the tumors, the optimization of blood pressure, as well as intravascular volume, is an important measure to avoid and suppress perioperative adverse hemodynamic events. Preoperative preparation includes the use of alpha-adrenergic antagonists, beta-adrenergic antagonists with or without other antihypertensive agents, fluid therapy as well as insulin therapy for hyperglycemia if required. Due attention should be given to type and dose of alpha-receptor antagonists to be used and the duration of this therapy to achieve an optimal level of preoperative "alpha-blockade." Despite this preoperative preparation, many patients will have hypertensive crises intraoperatively which need to be promptly and carefully managed by the anesthesia team which requires intensive and advanced monitoring techniques. The most common complication after tumor removal is hypotension which may require fluid therapy and vasopressor support for a few hours. With advancement in surgical and anesthetic techniques, the incidence of severe morbidity and mortality associated with the surgery is low in high volume centers.

Selective α1-adrenoceptor antagonist (controlled release tablets) in preoperative management of pheochromocytoma

The objective of this article is to evaluate the efficacy of Doxazosin Mesylate Controlled Release Tablets for preoperative treatment of patients with pheochromocytoma. Between 2003 and 2008, 67 patients with confirmed diagnoses of pheochromocytoma were enrolled in this study. According to the drug used in preoperative management, patients were divided into two groups: Doxazosin Mesylate pretreatment group (n=36) and Phenoxybenzamine pretreatment group (n=31). Surgery was performed only in patients who met the optimal preoperative condition. The hematocrit decreased significantly (P<0.001) after antiadrenergic therapy in patients pretreated with phenoxybenzamine or doxazosin. There was no significant difference between the fluid intakes during operation in both groups. The systolic arterial pressures both before and after induction of anesthesia were all significantly higher in the doxazosin patients than in the phenoxybenzamine group (P<0.05). After tumor removed, the lowest systolic arterial pressure was significantly higher in doxazosin group than in phenoxybenzamine group (P<0.05). The fluctuation of systolic arterial pressure during operation was more stable in doxazosin group than in phenoxybenzamine group (P<0.05). Doxazosin mesylate controlled release tablet was as effective as phenoxybenzamine in preoperative volume expansion. Although phenoxybenzamine provided better arterial pressure control, patients pretreated with DOX experienced more stable perioperative hemodynamic changes, shorter preoperative management periods and more simple medication.

Normotensive pheochromocytoma: institutional experience

We report an audit of nine cases of subclinical or normotensive pheochromocytoma managed in our department. This is the first report from India of such a series. During the period 1990-2003 a total of 45 patients of pheochromocytoma were diagnosed and managed in the Department of Endocrine Surgery, Sanjay Gandhi Postgraduate Institute of Medical Sciences. Among them, nine patients were diagnosed as having subclinical or normotensive pheochromocytoma. Inclusion criteria for normotensive pheochromocytoma were: no previous history of hypertension clinically and, in the previous treatment documents, any episode of symptoms suggesting high blood pressure. The demographic profile, clinical presentation, biochemical investigations, imaging results, surgical notes, and follow-up record were reviewed retrospectively. All patients had a primary complaint of flank/abdominal pain and were normotensive. Seven had elevated urinary metanephrine levels, and one patient had normal values. One patient did not undergo the urinary metanephrine assay. Imaging of the abdomen showed seven adrenal and two extra-adrenal masses (eight had computed tomography scans of the abdomen, and one underwent ultrasonography). After selective alpha-adrenergic blockade (prazosin), surgery was performed. Six patients required infusion of sodium nitroprusside intraoperatively. The final histopathology was pheochromocytoma in all patients. Metanephrine levels were normal during the follow-up. Normotensive pheochromocytomas are a distinct entity, and all adrenal incidentalomas should be investigated for catecholamine hypersecretion. We support the use of preoperative alpha-adrenergic blockade, and these patients should be treated along the same lines as hypertensive pheochromocytoma.

The Perioperative Management of a Patient with Complex Single Ventricle Physiology and Pheochromocytoma

Pheochromocytoma is associated with intense physiologic effects of alpha- and beta-adrenergic stimulation from catecholamine secretion. Perioperative management for these patients includes alpha-adrenergic receptor blockade, intravascular volume replacement, and, if necessary, beta-adrenergic receptor blockade. Significant perioperative changes in preload and afterload, fluid status, heart rate and rhythm, and inotropy can occur and may be contrary to anesthetic management goals for patients with certain conditions of congenital heart disease. We report the perioperative management with doxazosin of a patient with single ventricle physiology and cavo-pulmonary and aorto-pulmonary lung perfusion who presented for resection of a pheochromocytoma.

Long-term efficacy of doxazosin plus atenolol in the management of severe and sustained arterial hypertension and reversibility of the cardiac damage induced by chronic cathecolamine excess. A case report in a young girl with recurrent, functioning paraganglioma

Herein we report on a young girl with recurrent, functioning paraganglioma of the organ of Zuckerkandl and severe and sustained arterial hypertension (systolic pressure >200, diastolic pressure >120 mmHg); with evidence of cardiac damage induced by chronic cathecolamine excess. She promptly and steadily improved after the institution of doxazosin (6 mg/day) plus atenolol (50 mg bid) treatment. This case demonstrates that a correct therapeutic strategy in the long-term management of patients with inoperable catecholamine-producing neuroendocrine tumors (pheochromocytomas and paragangliomas) can maintain arterial pressure in the normal range and reverse the cardiac damage induced by chronic cathecolamine excess.

Surgical management of pheochromocytoma

The early diagnosis and safe treatment of pheochromocytoma have become possible due to advances in preoperative imaging techniques and endocrine tests, as well as improvements in the control of blood pressure and hemodynamics before and during the operation using various drugs. This article outlines the use of meticulous surgical technique via various approaches for open surgery and gives a step-by-step description of the methods for laparoscopic surgery. Such techniques have made the excision of pheochromocytoma safe and easy, allowing hypertension to be surgically cured in these patients. Thus, pheochromocytoma is less likely to be fatal than before. However. it is necessary to follow these patients for a long period postoperatively because it is often difficult to distinguish benign from malignant tumors and recurrence has been reported even more than ten years postoperatively.

Human pheochromocytoma: different patterns of catecholamines and chromogranins in the intact tumour, urine and serum in clinically unsuspected cases

Clinically unsuspected pheochromocytoma is usually discovered either at autopsy or during surgical intervention for unrelated conditions, despite often enormous neoplastic masses producing and storing catecholamine (CA). In order to assess whether these tumours share some common features we have compiled data for six patients admitted to hospital without previous diagnosis of their pheochromocytoma. The clinical variables and the morphological and immunohistochemical characteristics of the tumours revealed that these cases represented quite different expressions of adrenomedullary neoplasms. They differed not only with respect to nuclear ploidity and overall cytoplasmic morphology but also in catecholamine storage and expression of immunoreactive chromogranin A sequences in the intact tissue. In two of the patients hypertension had been overlooked as a diagnostic indicator of their CA-producing tumours. There was no clear relationship between the mean arterial pressure, the tumour content of CA and the serum levels of CA. Processed chromogranin A dominated in the serum of the two hypertensive cases. The 24-h urine values of CA and its main metabolite (vanillin mandelic acid) were, together with the serum values of chromogranin A and B, proportional to tumour mass and provided the most reliable diagnostic indicators for the non-hypertensive as well as the hypertensive cases.

Pheochromocytoma. Update on diagnosis, localization, and management

Pheochromocytoma, although rare, is associated with a high degree of morbidity and mortality if not recognized. A high degree of suspicion in patients with new-onset hypertension; hypertension with sudden worsening or development of diabetes mellitus; or a family history of MEN, neuroectodermal tumors, or simple pheochromocytoma should prompt biochemical confirmation with either 24-hour urine catecholamines (norepinephrine and epinephrine) or total MET (NMET plus MET). Following confirmation of the diagnosis, radiologic studies with CT and (if needed) MIBG are employed to localize the tumor. Surgical removal is the only definitive therapy. Medical management with alpha-blocking agents, to control symptoms and prevent a hypertensive crisis, is generally advocated for 2 weeks preoperatively and intraoperatively. Occasionally, beta-blockers, employed only after adequate alpha-blockade, are necessary to control tachycardia and tachyarrhythmias. High-dose MIBG and combination chemotherapy have been used adjunctively to treat malignant pheochromocytoma, although neither modality provides lasting satisfactory results. Normal urine assays performed 2 weeks postoperatively ensure the complete removal of all tumor. Additionally, lifelong follow-up (yearly initially) is necessary to detect any signs of benign recurrence or malignancy because these have been reported to occur as long as 41 years after the initial surgical resection. Biochemical evidence of excess catecholamine production usually precedes the clinical manifestations of catecholamine excess when these tumors recur.

Efficacy of doxazosin in specific hypertensive patient groups

In practice, some of the major problems for the physician who treats hypertension are patients who are resistant to treatment or who have other complicating risk syndromes. Therefore the overall efficacy of an antihypertensive agent must include an assessment of effect in patients with serious ancillary problems. In this article, doxazosin is reviewed for its efficacy in the treatment of severe essential hypertension and specific complications or conditions of mild or moderate essential hypertension, namely, left ventricular hypertrophy, hyperlipidemia, noninsulin-dependent diabetes mellitus, renal insufficiency, pheochromocytoma, chronic obstructive pulmonary disease, peripheral vascular disease, and smoking. Doxazosin is particularly efficacious in many specific subgroups of patients with hypertension, and the results of relevant studies are discussed.

Clinical pharmacotherapeutics of doxazosin

Doxazosin is the latest in a series of highly selective postsynaptic alpha 1-adrenoceptor inhibitors. It is readily absorbed, with high bioavailability and a relatively long plasma half-life, neither of which property is influenced by age. This accounts for the prolonged pharmacologic activity of doxazosin following a single oral dose. Its prime pharmacodynamic activity resides in its ability to counter sympathetic vasoconstriction of the systemic arteriolar resistance vessels and venous capacitance system, which enables the drug to target the major pathophysiologic abnormality in hypertension, i.e., the generalized systemic arteriolar constriction. The widespread vasodilation induced by doxazosin relieves both cardiac preload and afterload and, consequently, reduces left ventricular wall stress and myocardial oxygen consumption. In hypertension, doxazosin reduces blood pressure both at rest and during exercise by reduction of systemic vascular resistance without precipitating substantial reflex cardiac stimulation. The effects are maximal on the standing blood pressure between two and four hours after ingestion; due to doxazosin's relatively slow absorption, postural hypotension is infrequent. Its antihypertensive activity is maintained over 24 hours following a single oral dose, and the optimal dose range is 2 to 8 mg once daily. The antihypertensive efficacy of doxazosin has been shown to be comparable with that of other alpha-adrenoceptor inhibitors, beta-blocking drugs, diuretics, calcium antagonists, and angiotensin-converting enzyme inhibitors. In contrast to other conventional antihypertensive drugs, a unique feature of alpha-adrenoceptor-inhibiting drugs, including doxazosin, is their ability to reduce the plasma concentrations of triglycerides, total cholesterol, and low-density lipoprotein cholesterol and to increase high-density lipoprotein cholesterol concentration. This contrasts with the opposite effect on lipid levels induced by hydrochlorothiazide and atenolol seen in comparative studies. Side effects show no predilection for any organ system, and the overall incidence of such effects compares well with those of other commonly used antihypertensive drugs. This unique combination of antihypertensive efficacy and favorable effect on blood lipid levels indicates that once-daily treatment with doxazosin holds considerable promise in the treatment of hypertension, both from the point of view of its antihypertensive efficacy and also from its primary preventative potential.