The clinical impact of 1:1 conversion from Neoral to a generic cyclosporine (Gengraf) in renal transplant recipients with stable graft function

The introduction of cyclosporine (CYA) to the immunosuppressive armamentarium has had a significant effect on graft survival. An improvement in the formulation from the oil-based to a microemulsion-based form has resulted in better absorption and more predictable CYA bioavailability. Since the introduction of the first microemulsion form (Neoral), several bioequivalent formulations are now available and are switched in a 1:1 fashion at pharmacies to curtail costs. The purpose of our study was to study the effect of a 1:1 switch from Neoral to Gengraf on CYA trough levels and serum creatinine (SRC) in renal transplant recipients with stable graft function. Eighty-two renal transplant recipients with stable graft function were enrolled in the study, and of these, 73 were switched to Gengraf, whereas nine remained on Neoral. The 13 patients switched to Gengraf required a dosage change after the mean CYA trough levels changed from 234 +/- 96 ng/mL at baseline to 289 +/- 102 ng/mL (p < 0.05) at 2 wk. With the adjustments in dosage, the levels approached the baseline trough concentrations (239 +/- 151 ng/dL). The nine patients who remained on Neoral had no change in the CYA levels or SCR. Nearly 20% of patients who switched to a bioequivalent CYA preparation required a dose adjustment to return to pre-conversion CYA trough levels. Our study raises serious concerns regarding the switchability of generic CYA for Neoral without careful follow-up therapeutic drug monitoring.

Anti-CD20 monoclonal antibody (Rituximab) for life-threatening hemolytic-uremic syndrome

Rituximab is a chimaeric monoclonal antibody directed against the CD20 antigen. It has been successfully used in B-cell malignancy and its efficacy in the treatment of in autoimmune hemolytic anemia and other autoimmune diseases is being investigated. There are also few case reports of its success in thrombotic thrombocytopenic purpura, but no reports of its use in hemolytic-uremic syndrome (HUS). We report a 36-year-old patient who had lost the function of her native kidneys secondary to HUS. After more than 1 year in clinical remission, she received a living unrelated kidney transplant. This immediately precipitated a severe relapse of HUS. The process was abrogated but not completely inactivated, despite over 40 plasma exchange treatments. Consequently, she was given Rituximab in courses of two to three doses, each dose 375 mg/m(2), at weekly intervals with remarkable stabilization of her disease for approximately 6 months.

Human immunodeficiency virus-associated nephropathy: a primary care perspective

The advent of highly active antiretroviral therapy represents a significant advance in medical care for human immunodeficiency virus (HIV)-infected persons. However, not everyone has derived the expected benefits of antiretroviral therapy and HIV-associated diseases such as nephropathy still occur in at-risk populations. Currently, there are no recommendations for screening HIV-positive patients for HIV-associated nephropathy. We propose semiannual screening for proteinuria in HIV-positive African Americans and patients with a family history of renal disease, and provide an algorithm for evaluation.

Randomized, open-label preference study of two cyclosporine capsule formulations (usp modified) in stable solid-organ transplant recipients

BACKGROUND

Prior research has indicated patient dissatisfaction with the odor, size, and taste of cyclosporine capsules, as well as the halitosis and body odor the capsules can cause.

OBJECTIVES

The purposes of this investigation were to (1) compare the overall cyclosporine capsule preference (Gengraf vs Neoral) in stable, solid-organ transplant recipients, (2) assess patient preference based on specific capsule attributes, and (3) determine the reliability of the Cyclosporine Capsule SatiSfaCtion Survey (original to this study).

METHODS

In this multicenter, randomized, open-label, parallel-group, preference study, patients were recruited from 144 centers in North America with established transplant programs. Solid-organ transplant recipients who had taken stable doses of cyclosporine (Neoral) for >/=2 consecutive months were randomized in a 9:1 ratio to receive another cyclosporine formulation (Gengraf) or to remain on Neoral therapy. Patients completed the Cyclosporine Capsule Satisfaction Survey prior to randomization (baseline survey) and after taking the study drug for 4 weeks (final survey). The survey consisted of multiple attribute items with high face validity in assessing patients' perceptions and preferences with regard to their overall experience, as well as specific attributes of cyclosporine capsules known to affect patient acceptance.

RESULTS

The intent-to-treat population included 1906 patients (1211 men, 693 women [sex unknown in 2 patients]; mean [SD] age, 50.2 [12.4] years). A total of 1708 patients were switched to Gengraf; 198 continued on Neoral. Based on their overall experience with both capsule formulations, the majority of patients switched to Gengraf (61.9%) responded that they preferred the Gengraf capsule, compared with 13.7% who preferred the Neoral capsule and 24.4% who indicated no preference (P < 0.001). A similar preference for Gengraf was observed based on capsule odor (66.3%), ease of swallowing (51.5%), taste (57.1%), and impact on breath odor (52.5%) and body odor (48.4%) (P < 0.001 for each test). The results of internal consistency and reproducibility calculations were high for the Cyclosporine Capsule Satisfaction Survey. Internal consistency ranged from alpha = 0.84 to 0.95 for the subscales and was alpha = 0.95 for the overall score. Ranges for reproducibility in the subscales were r = 0.75 to 0.79, with an overall reproducibility of r = 0.85. Guyatt's responsiveness statistics for the subscale and overall scores were moderately high to very high, indicating that the survey is capable of measuring change in response to treatment.

CONCLUSIONS

Of the transplant recipients receiving Gengraf in this study, most preferred Gengraf to Neoral based on overall experience, capsule odor, difficulty swallowing, taste, breath odor, and body odor. Among all study patients, fewer patients receiving Gengraf were bothered by capsule odor, difficulty in swallowing, taste, or the impact on breath or body odor compared with patients who continued to receive Neoral. Internal consistency, reproducibility, and responsiveness results show that the Cyclosporine Capsule Satisfaction Survey is a psychometrically valid instrument that is appropriate for use in clinical trials.

Donor calculi induced acute renal failure

Nephrolithiasis is an infrequent complication following renal transplantation and acquisition of a stone with the donor kidney is rare. Indeed only a few cases of donor stones causing renal failure have been reported. Since the grafted kidney is denervated, stone disease may not present with the classic renal colic but rather with acute renal failure secondary to the obstruction. Identification of the precise cause is critical in order to avoid inappropriate therapy. We present our experience of two renal transplant patients who developed obstructive uropathy by stones originating from the donor kidneys.

Thromboxane receptors in human kidney tissues

Thromboxane (TX) A2 effects in the kidneys include contraction of glomerular mesangial cells and intrarenal vascular tissue. A kidney cDNA encoding a TX receptor expressed in rat renal glomeruli and rat renal arterial smooth muscle cells has been reported. However, TXA2 receptors in human kidneys have not been documented. The purpose of this study was to identify and characterize TXA2 receptors in glomeruli and intrarenal arteries isolated from human kidneys. Normal kidneys, not used for transplant because of technical reasons, were kept at -70 degrees C and used for research purposes. The glomeruli and intrarenal arteries were isolated from renal cortical tissue by a mechanical sieving technique. The equilibrium dissociation constant and receptor number were determined by nonlinear analysis of binding inhibition data. The data were generated in radioreceptor assays using [125I]-BOP, a stable analog of TXA2. The dissociation constants (mean +/- SEM) for binding of I-BOP to human glomeruli and intrarenal arterial membranes were 6.6 +/- 1.1 nM (n = 7) and 20 +/- 6 nM (n = 7), respectively (p < 0.05). The receptor number was 311 +/- 91 fmol/mg protein (n = 7) in glomeruli and 74 +/- 16 fmol/mg protein (n = 7) in intrarenal arterial membranes (p < 0.04). The order of specificity of TXA2 analogs for [125I]-BOP binding sites was similar in glomeruli and in arterial membranes and was I-BOP > or = U46619 > or = pinane TXA2 > or = carbocyclic TXA2 > or = PGH2. These findings provide direct evidence for the presence of specific, high-affinity [125I]-BOP binding sites in human renal glomeruli and extraglomerular vascular tissue. These data also indicate that the human binding sites have higher affinity for the TXA2 agonist I-BOP than for PGH2.

Hemodynamic and renal effects of U-46619, a TXA2/PGH2 analog, in late-pregnant rats

The vasoconstrictor effects of pressor agents are attenuated during pregnancy. Thromboxane A2 (TXA2) is produced in great quantities during hypertension in pregnancy, and therefore it is important to know whether pregnancy modifies the pressor effects of TXA2. The TXA2 analog U-46619 was infused in anesthetized, acutely prepared and conscious, chronically prepared late-pregnant and nonpregnant female rats to examine its systemic hemodynamic and renal effects. Mean arterial pressure (MAP) and total peripheral resistance (TPR) were lower in anesthetized pregnant than nonpregnant rats (P < 0.01). The infusion of U-46619 into the aortic arch resulted in elevation of MAP only in pregnant rats, due to a greater elevation of TPR (60 +/- 17%) compared with nonpregnant rats (36 +/- 6%, P < 0.05). The pressor effect of intravenously infused U-46619 was also enhanced in conscious pregnant versus nonpregnant rats, and the increase in renal vascular resistance was undiminished. U-46619 increased hematocrit and plasma protein concentration more during pregnancy, which suggested greater reduction of plasma volume. The urinary excretion of sodium (-1.49 +/- 0.25 vs. -0.54 +/- 0.24 micromol/min) and water was reduced more in pregnant than nonpregnant rats during U-46619 (P < 0.01). Thus the MAP and renal effects of the TXA2 analog are exaggerated during pregnancy in the rat.

CD4+ and CD8+ lymphocyte and cortisol response patterns in elderly and young males after methylprednisolone exposure

The elderly have impaired cellular immunity and are more predisposed to opportunistic infections after long term glucocorticoid treatment. No data, examining the response of lymphocyte subsets (CD4+, CD8+) under baseline conditions and after exposure to methylprednisolone in young and elderly males, are available. This crossover study examined lymphocyte subsets and cortisol response patterns in seven elderly males (66-82 years) and five young males (24-37 years) randomized into Phase I (24 hr baseline) and Phase II (10 mg intravenous dose of methylprednisolone). Whole blood samples were obtained at 0, 4, 8, 12 and 24 hr to determine total lymphocytes and CD4+ and CD8+ cells utilizing monoclonal antibodies and flow cytometry. The absolute number of lymphocyte subsets and the lymphocyte area under the time curve (AUC) were measured and a 12 and 24 hr lymphocyte response ratio (AUC Phase II divided by AUC Phase I) was determined. Serial plasma samples over 24 hours were collected to quantitate cortisol (Phase I) and methylprednisolone concurrent with cortisol (Phase II). Pharmacokinetic parameters were generated and the cortisol AUC was determined. The AUC values for lymphocytes and cortisol from Phase II quantitated the pharmacologic response to methylprednisolone exposure while Phase I data described the interpatient variability in these parameters. Diurnal patterns for lymphocytes and cortisol were noted in all subjects during Phase I. The mean CD4+ and CD8+ lymphocyte AUC from 0 to 24 hr during Phase I was significantly smaller for the elderly when compared to young men. However, after exposure to methylprednisolone, lymphopenia occurred in all subjects with a mean decline of 54% in the elderly and 60% (p = 0.44) in young subjects for the total lymphocyte count and returned to baseline by 8-12 hr. During Phase II, the CD4+ lymphocytes (72% decline in elderly; 70% in young; p = 0.71) demonstrated a more notable decline than CD8+ cells (44% decline in elderly; 52% in young; p = 0.31) with a nadir occurring between 4 to 6 hr for both subsets. The lymphocyte response ratio was not significantly different between groups for total, CD4+, and CD8+ cells at 12 hr or 24 hr determinations. A slower clearance of methylprednisolone was noted in the elderly (mean: 256 mL/hr/Kg) than in the young men (mean: 359 mL/hr/Kg; p < 0.05) during Phase II with no significant difference found between groups for volume of distribution, elimination rate constant or half-life. A significantly smaller cortisol suppression ratio [0.36+/-0.11 (elderly) versus 0.58+/-0.11 (young), p = 0.01] which indicates a more profound cortisol suppression was noted. A significant correlation of -0.61 (p < 0.05) between drug exposure (methylprednisolone AUC) and pharmacologic effect (cortisol suppression ratio) was noted for the combined data in the young and elderly males. During Phase I, the CD4+ and CD8+ lymphocyte AUC was significantly smaller in the elderly. A definite suppression pattern for total, CD4+ and CD8+ lymphocytes and cortisol was noted after methylprednisolone exposure in young and elderly males. An age-dependent suppression of cortisol during Phase II was noted but the degree of lymphopenia after drug exposure did not differ between the young and elderly group for any of the cell subsets. These data from healthy elderly provide a basis for further studies to assess immunologic and endocrinologic responses among elderly patients requiring chronic glucocorticoid therapy.

Cortisol pharmacodynamics after methylprednisolone administration in young and elderly males

Glucocorticoids are commonly prescribed in the elderly on an empiric basis with little consideration for the age-related alterations in pharmacologic response. The objectives of this study were to compare the effect of methylprednisolone on cortisol patterns in elderly and young healthy men, to define the relationship between pharmacokinetic parameters of methylprednisolone and pharmacodynamics of cortisol in the elderly and young men. Seven healthy, elderly males (69-82 years old) and five healthy, young males (24-37 years old) participated in a 24-hour pharmacodynamic trial with randomized assignment to a control period (Phase 1) and a methylprednisolone period (Phase II). Serial blood samples were obtained throughout both study periods. Cortisol measurements included the total area under the concentration-time curve (AUC), return AUC, and suppression ratio. During Phase I, a circadian pattern was noted in both groups. After exposure to methylprednisolone (Phase II), a linear decline in serum concentrations of cortisol was observed in both groups. The return AUC of cortisol (425 +/- 357 ng.hr/mL [elderly] versus 854 +/- 216 ng.mL [young]) and the total AUC 764 +/- 340 ng.h/mL [elderly] versus 1,230 +/- 258 ng.hr/mL [young]) were significantly lower in the older men. In addition, a significant decline in total AUC and nadir concentration of cortisol from Phase I to Phase II was noted within both groups. The suppression ratio was significantly greater in the elderly men (mean, 0.38 versus 0.58 in young), which indicates a greater degree of adrenal suppression after administration of methylprednisolone. Exposure to methylprednisolone, as measured by AUC, was 554 +/- 215 ng.hr/kg (elderly) and 389 +/- 102 ng.hr/kg (young). The greater exposure to methylprednisolone noted in the elderly yielded significant combined correlations for both groups with AUC, return AUC, and suppression ratio of cortisol. A more significant response of cortisol to the exogenous glucocorticoid was apparent in the elderly men. In addition, a slower clearance of methylprednisolone was noted in the elderly group compared with their young counterparts. The effect of reduced clearance of methylprednisolone on the suppression ratio indicates the interrelationship between the disposition of a single dose of an exogenous glucocorticoid and response patterns of cortisol.

Methylprednisolone and cortisol metabolism during the early post-renal transplant period

Despite the widespread use of methylprednisolone and the well-appreciated effects of this drug on HPA suppression, little data is available which describes individual patient exposure to both methylprednisolone and cortisol following renal allograft placement. The clinical utilization of methylprednisolone during the early post-transplant period is based upon standardized dosing protocols that do not consider factors which may influence the pharmacokinetics of this drug during the post-transplant period. Therefore, this study was designed to examine the pharmacokinetics of methylprednisolone (mean dose: 28 mg) and cortisol pharmacodynamics in 9 renal transplant recipients (4 females; 5 males) who were studied during the early post-transplant period (5 to 12 days after surgery). All patients (mean serum creatinine: 1.4 +/- 0.3 mg/dl) had serial blood samples collected over a 12- to 24-hour period (depending upon the dosing schedule) which were analyzed concurrently for methylprednisolone and cortisol. A three-fold variation in drug clearance ranging from 174 to 638 ml/h/kg with a range in the volume of distribution of 0.83 to 2.24 l/kg and resultant half-lives ranging from 1.20 to 3.02 hours was noted. The cortisol response was quantitated by a 12-hour cortisol area under the curve (C-AUC12) to examine the interpatient cortisol patterns during the early post-transplant period. C-AUC12 ranged from 44.0 to 636 ng.h/ml. Significant correlations were noted between the cortisol plasma concentration at 12 hours and methylprednisolone clearance and area under the concentration versus time curve (AUC). Interpatient variability in the disposition of methylprednisolone and cortisol response noted during the early post-transplant period contradict the clinical assumptions which underlie the fixed dosing protocols currently utilized for methylprednisolone.

Pregnancy enhances the pressor response to thromboxane analogues in rabbits

In this study, we first tested the hypothesis that the previously demonstrated circulatory failure and thrombocytopenia induced by intracaval administration of thromboxane A2 (TxA2) analogues in nonpregnant (NP) rabbits [G. Losonczy, I. Mucha, J. DiPirro, J. Sweeney, G. Brown, J. Brentjens, and R. Venuto. Am. J. Physiol. 265 (Regulatory Integrative Comp. Physiol. 34): R772-R780, 1993] could be avoided if the compounds were given instead into the aortic arch. Conscious New Zealand White rabbits received bolus injections of U-46619 (5-20 micrograms) through a previously implanted catheter threaded into the aortic arch. Indeed, mean arterial pressure (MAP) rose modestly, and thrombocytopenia did not develop. Next, we compared the blood pressure responses of pregnant (P) rabbits with those of NP rabbits to intra-aortic U-46619 and I-BOP, because they had been found to be resistant to both the hypotensive and platelet aggregatory effects of intracaval U-46619. Resting blood pressure was lower in P than in NP rabbits (74 +/- 3 vs. 95 +/- 2 mmHg), but showed a greater increase in response to U-46619. For example, following a 20-micrograms dose blood pressure rose 20 +/- 0.3 mmHg in P vs. 12 +/- 2.1 mmHg in NP rabbits (P < 0.02). Similar results were obtained with the second TxA2 analogue I-BOP. Pregnancy-induced enhancement of blood pressure elevation may be the consequence of peripheral vasoconstriction, which was not seen in NP rabbits. Thus the actions of TxA2 analogues U-46619 and I-BOP are markedly influenced by the route of administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Post-transplant diabetes mellitus and methylprednisolone pharmacokinetics in African-American and Caucasian renal transplant recipients

Post-transplant diabetes among renal transplant recipients is more prevalent in the African-American population. However, it is unknown if methylprednisolone (a commonly prescribed glucocorticoid in transplant patients) pharmacokinetics is altered among African-American renal allograft recipients compared to Caucasian counterparts. Therefore, the objectives of this study were to identify the occurrence of post-transplant diabetes in our clinic population and to characterize the pharmacokinetics of methylprednisolone among our African-American and Caucasian renal transplant recipients. A retrospective chart survey was done on African-American and Caucasian recipients with stable renal function and no history of diabetes pre-transplantation in order to characterize the occurrence of post-transplant diabetes in our clinical population. The survey was conducted from January 1985 to January 1992 in recipients with graft survival of at least 3 months. Post-transplant diabetes was defined as two fasting glucose serum concentrations greater than 140 mg/dl or one random serum glucose concentration greater than 200 mg/dl which was confirmed by a fasting serum glucose value greater than 140 mg/dl and a 2 hour post-prandial greater than 200 mg/dl. A 24-hour pharmacokinetic evaluation was conducted in a sub-group of African-American and Caucasian patients after intravenous administration of methylprednisolone. Over the survey period, 75 renal transplants (30 females; 45 males) were performed and 50 of these transplant recipients (24 females; 26 males) were not diabetic prior to the allograft placement. Of these 50 patients, 22 males and 17 females fulfilled the inclusion criteria established for the retrospective survey.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics of methylprednisolone during acute renal allograft rejection

High dose methylprednisolone is administered empirically by fixed daily boluses to renal transplant recipients who are experiencing acute rejection episodes. Little information is available characterizing the pharmacokinetics of high-dose methylprednisolone in these individuals, who are often acutely ill. Therefore, 5 renal transplant recipients (2 men; 3 women) were studied during an acute rejection episode (mean serum creatinine = 2.6 +/- 0.7 mg/dl) which occurred within the first 8 months post-transplantation. The rejection episode was characterized clinically by at least two of the following: fever, leukocytosis, graft tenderness and an increase in serum creatinine. All patients received bolus doses of methylprednisolone for 3 consecutive days during the rejection episode. All patients were studied on the 3rd day of bolus dosing and received 250 mg methylprednisolone by an i.v. infusion. In phase II, 4 patients were studied during a period of stable renal function when the methylprednisolone was given at lower chronic immunosuppressive doses. Serum samples were taken prior to infusion and serially over the following 24 hours. The serum samples were analyzed for methylprednisolone with high-performance liquid chromatography (HPLC) and pharmacokinetic parametes were generated. During rejection episodes, the methylprednisolone clearance values were 523 +/- 154 ml/h/kg with a corresponding mean volume of distribution of 1.89 +/- 0.72 l/kg. The mean methylprednisolone half-life was 2.61 +/- 0.62 h. During Phase II, the methylprednisolone clearance was 358 +/- 95 ml/h/kg with a half-life of 3.05 h. This observation indicates that methylprednisolone metabolism is increased during acute rejection compared to that seen during chronic immunosuppressive dosing with this agent.

Methylprednisolone pharmacokinetics, cortisol response, and adverse effects in black and white renal transplant recipients

It is generally assumed that chronic glucocorticoid therapy is similar pharmacologically when administered to either black or white renal transplant recipients, resulting in adrenal suppression, low circulating plasma cortisol concentrations, and a similar degree of drug exposure and toxicity. To examine this theory and to investigate the relationship of glucocorticoid metabolism to steroid-induced adverse effects among specific ethnic groups of renal transplant recipients, 9 black and 9 white male patients chronically receiving methylprednisolone were enrolled. All patients had stable renal function and were matched for age, weight, and time since transplant. Standard pharmacokinetic parameters for methylprednisolone were determined and cortisol responses were characterized by total cortisol area under the concentration curve (AUC), return cortisol AUC, and cortisol suppression half-life. All patients received their daily oral dose of methylprednisolone (mean daily dose = 11 mg for blacks and 11 mg for whites) as an intravenous infusion with serial plasma samples obtained over 24 h. The patients were assessed for the presence of specific cushingoid manifestations (buffalo hump, moon facies) and steroid-associated diabetes. Methylprednisolone and cortisol were analyzed via HPLC. In the black patients, the mean clearance of methylprednisolone (206 +/- 70 ml/hr/kg) was significantly slower with a smaller volume of distribution (0.95 +/- 0.32 L/kg) when compared with the white group (327 +/- 129 ml/hr/kg, P = 0.03; volume of distribution = 1.33 +/- 0.27 L/kg, P = 0.015). Despite chronic methylprednisolone therapy, a definite 24-hr cortisol response pattern was noted in 15 of the 18 patients with a mean total cortisol AUC of 732 +/- 443 ng.hr/ml in blacks and 539 +/- 361 ng.hr/ml in whites (P = 0.17, black vs. white). The mean cortisol suppression half-life was 4.31 +/- 1.54 hr in black recipients and 4.11 +/- 1.49 hr in whites (P = 0.48). The mean return cortisol AUC for the black patients was 327 +/- 279 ng.hr/ml and 370 +/- 207 ng.hr/ml for white patients (P = 0.28). The serum cortisol nadir for black patients was 12.3 +/- 7.2 ng/ml, which was significantly higher than the cortisol nadir in white patients (6.4 +/- 4.4 ng/ml; P = 0.03). A majority (94%) of patients (9 black, 8 white) had moon facies and 27% of patients (3 black, 1 white) had a buffalo hump. While 5 of 9 black patients had steroid-associated diabetes, no white patients manifested this adverse effect. The black patients with diabetes had higher cortisol AUCs with lower methylprednisolone clearances than the white group.(ABSTRACT TRUNCATED AT 400 WORDS)

Repeated assessment of methylprednisolone pharmacokinetics during chronic immunosuppression in renal transplant recipients

OBJECTIVE

To compare the pharmacokinetics of methylprednisolone in renal transplant recipients on 2 occasions separated by at least 1 month during chronic immunosuppression.

DESIGN

A prospective unblinded trial.

PATIENTS

Ten renal transplant recipients (aged 25-62 years) evaluated in a public university-affiliated hospital clinic.

INTERVENTIONS

All patients received their chronic oral dose of methylprednisolone as a 10-20-minute intravenous infusion during the 2 study periods.

MAIN OUTCOME MEASURES

Serum methylprednisolone concentrations were determined by HPLC and were used to generate the pharmacokinetic parameters of the drug.

RESULTS

During study 1, which ranged from 1.2 to 24 months posttransplant, the mean +/- SD methylprednisolone dose was 13.2 +/- 6.4 mg. In study 2 (2.5-38.5 mo posttransplant), the mean dose was 10.6 +/- 3 mg. During both study periods, methylprednisolone concentrations exhibited a monoexponential decline. Considerable variability in methylprednisolone clearance was observed between periods in certain patients. Four of the 10 patients demonstrated a reduction in clearance from study 1 to study 2, which ranged from a 28% to a 53% decrease. Two patients exhibited an increase in clearance of 40% and 49%. The mean +/- SD total body clearance in study 1 was 363 +/- 330 mL/min/kg, whereas the mean volume of distribution was 1.18 +/- 0.53 L/kg. The mean elimination rate constant was 0.29 +/- 0.14 h-1, with a mean serum half-life of 2.87 +/- 1.15 h during the first phase. In study 2, the mean methylprednisolone clearance was 261 +/- 150 mL/min/kg (p > 0.05) and the mean volume of distribution was 0.89 +/- 0.31 L/kg (p > 0.05). The mean serum half-life of methylprednisolone was 2.91 +/- 0.60 h (p > 0.05), with the mean elimination rate constant of 0.25 +/- 0.06 h-1 (p > 0.05).

CONCLUSIONS

These data demonstrate that intrapatient variability in methylprednisolone clearance exists among certain renal allograft recipients. As a result of the observed variability, patients who are continued on the same dose of methylprednisolone during the posttransplant period of chronic immunosuppression will be subjected to a changing pattern of exogenous glucocorticoid exposure. The impact of these changing patterns requires further prospective evaluation.

A proposed method for the noninvasive evaluation of renal asymmetry in a living-related donor candidate

This report proposes an adjunctive technique for the evaluation of asymmetry of renal size and function of undetermined etiology, discovered during the assessment of two living-related donor candidates. The method utilizes the observation of renal functional reserve measurement as demonstrated by oral protein loading in patients with normal and diseased kidneys. Renal function was measured as timed Ccr and estimation of differential GFR by technetium-99m diethylenetriaminepentaacetic acid (99mTcDTPA) scintigraphy. A comparison of renal function before and after protein loading in two such patients demonstrated the anticipated increase in GFR. No change in differential GFR as determined by renal scan in one patient was interpreted as supportive evidence for bilaterally normal parenchymal function. Follow-up of both donors shows continued normal renal function.

Pharmacokinetics of methylprednisolone in elderly and young healthy males

OBJECTIVE

To characterize and compare the pharmacokinetics of a single intravenous dose of methylprednisolone in elderly and young healthy males.

DESIGN

A randomized, parallel pharmacokinetic trial.

SETTING

A public university-affiliated hospital.

SUBJECTS

Seven healthy, elderly white males (aged 69 to 82 years) and five healthy, young white males (aged 24 to 37 years) who gave informed consent and fulfilled all screening criteria.

MEASUREMENTS

Serial blood samples were obtained over a 24-hour study period after intravenous administration of a 10-mg dose of methylprednisolone. Serum methylprednisolone concentrations were determined by high performance liquid chromatography and utilized to determine the pharmacokinetic parameters.

RESULTS

Methylprednisolone serum concentrations declined in a linear manner in both groups. However, 4 hours after the dose, the mean serum concentration of methylprednisolone was 50.9 +/- 15.1 ng/mL in the elderly group and 37.6 +/- 7.5 (P = 0.07) ng/mL in the young group. The clearance of methylprednisolone was 237 +/- 62 mL/h/kg, with a volume of distribution of 1.10 +/- 0.07 L/kg, for the elderly group, whereas the young males had a mean drug clearance of 359 +/- 90 mL/h/kg (P < 0.05) and a mean volume of distribution of 1.28 +/- 0.34 L/kg. The half-life of methylprednisolone ranged from 1.90 to 5.40 hours in the elderly group; the range was 1.99 to 3.31 hour (P = 0.016) in the young group.

CONCLUSION

A slower methylprednisolone clearance was noted in the elderly group compared with the young counterparts. This pharmacokinetic alteration seen in healthy elderly subjects may contribute to the increased incidence of adverse effects from chronic glucocorticoid therapy that has been observed among elderly patients.

The cytomegalovirus-antigenemia assay in the diagnosis of posttransplant cytomegalovirus infection

Cytomegalovirus (CMV) infection continues to be a major cause of morbidity and mortality in transplant recipients, yet prompt diagnosis remains a problem. A new assay has been developed that detects CMV antigens in peripheral blood leukocytes (CMV-AG). A retrospective analysis of the experience with this assay was performed, and its usefulness in the diagnosis of CMV infection in renal transplant recipients with unexplained fever was compared with that of conventional modalities (buffy coat culture, detection of circulating anti-CMV immunoglobulin M). The results suggest that the CMV-AG assay is a more rapid and sensitive test than existing modalities in the early diagnosis of CMV infection. When expressed quantitatively, it can discriminate between CMV infection and CMV disease, and it is useful in monitoring the course of infection and the response to therapy.

Cortisol pharmacodynamic response to long-term methylprednisolone in renal transplant recipients

STUDY OBJECTIVE

To examine the pharmacodynamic patterns of cortisol and pharmacokinetic values of long-term methylprednisolone in renal transplant recipients.

DESIGN

Twenty-four-hour pharmacokinetic and pharmacodynamic evaluation of patients who participated in a glucocorticoid-monitoring program.

SETTING

University-based renal transplant clinic.

PATIENTS

Fourteen renal transplant recipients studied during a clinically stable period.

INTERVENTIONS

The daily oral methylprednisolone dose for each patient was administered intravenously, and serial plasma cortisol and methylprednisolone samples were obtained over 24 hours.

MEASUREMENTS AND MAIN RESULTS

Methylprednisolone was analyzed by high-performance liquid chromatography. The baseline morning cortisol serum concentrations ranged from 9.8-210.7 ng/ml. After the drug was administered, cortisol declined in a linear fashion with a mean suppression half-life of 2.4 +/- 0.9 hours. The cortisol nadir was reached at 12-16 hours in 11 of 14 patients. The return cortisol area under the curve (AUC-Cret) was noted in all patients and ranged from 57-987 ng.hr/ml. The total cortisol area under the curve was greater in patients who had been transplanted for longer than 2 years (1676 +/- 252 vs 836 +/- 405 ng.hr/ml; p < 0.05) compared with more recently transplanted patients. Methylprednisolone clearance ranged from 100-1181 ml/hr/kg with a mean volume of distribution of 1.3 +/- 0.6 L/kg. The methylprednisolone half-life ranged from 1.2-4.7 hours. The correlation between AUC-Cret and methylprednisolone AUC was -0.64 (p < 0.05).

CONCLUSIONS

The pharmacodynamic response of cortisol in renal transplant recipients may be associated in part with long-term steroid exposure. However, the interrelationship between the endocrine and immune system may also affect cortisol's disposition and subsequent recovery patterns in this population. Considerable interpatient variability was apparent in both the cortisol pharmacodynamic response as well as the pharmacokinetics of methylprednisolone. These findings suggest a more individualized dosing method may be necessary to optimize the immunosuppressive effect of glucocorticoids and minimize clinical toxicity.

Racial differences in the pharmacokinetics of methylprednisolone in black and white renal transplant recipients

STUDY OBJECTIVE

To examine the comparative pharmacokinetics of long-term methylprednisolone therapy in black and white renal transplant recipients.

DESIGN

Comprehensive pharmacokinetic evaluations of patients who participated in our glucocorticoid-monitoring program.

SETTING

University-based renal transplantation clinic.

PATIENTS

Six white renal transplant recipients with stable renal function, sex- and (approximate) age-matched with six preselected black patients.

INTERVENTIONS

The daily oral methylprednisolone dose for each patient was administered intravenously, and serial plasma samples were obtained over 24 hours.

MEASUREMENTS AND MAIN RESULTS

Methylprednisolone was analyzed by high-performance liquid chromatography. The drug's pharmacokinetics in black and white patients, respectively, were as follows: mean clearance 234 +/- 124 and 472 +/- 180 ml/hr/kg (p < 0.05); volume of distribution 0.3-2.0 and 0.8-2.0 L/kg; and elimination rate constant 0.13-0.41 and 0.27-0.42 hour-1 (p < 0.06). No statistical difference was noted in the last two parameters. The mean half-life of 3.4 +/- 1.4 hours in black patients compared with 2.1 +/- 0.3 hours in white patients approached statistical significance (p < 0.08).

CONCLUSIONS

These preliminary observations suggest that the disposition of methylprednisolone differs between black and white renal transplant recipients. The current method of prescribing glucocorticoids employs a fixed-dose regimen that does not take these possible interracial differences into consideration. Incorporating the differences may allow for more individualized dosing and more efficacious use of the agent in this patient population.

Comparative methylprednisolone pharmacokinetics in renal transplant patients receiving double- or triple-drug immunosuppression

OBJECTIVE

To assess the pharmacokinetics of chronic methylprednisolone therapy in renal transplant patients receiving double-drug (methylprednisolone and azathioprine) and triple-drug (methylprednisolone, azathioprine, and cyclosporine) immunosuppression.

DESIGN

Parallel, randomized trial.

PATIENTS

Fourteen renal transplant recipients (aged 29-65 y) evaluated in a public, university-affiliated hospital clinic.

INTERVENTIONS

All patients received their chronic oral dose of methylprednisolone via a 10-20-minute intravenous infusion.

MAIN OUTCOME MEASURES

Serum methylprednisolone concentrations were determined by HPLC and were used to generate pharmacokinetic parameters for this drug.

RESULTS

The mean daily methylprednisolone dosage was 19 +/- 19 mg in the double-drug group and 9 +/- 2 mg in the triple-drug group. Mean serum creatinine concentrations were 124 +/- 44 and 124 +/- 27 mumol/L, respectively. Mean methylprednisolone clearances were similar in both groups: 405 +/- 205 (double-drug) and 373 +/- 365 mL/h/kg (triple-drug) (p > 0.05). Mean steady-state volume of distribution was 1.5 +/- 0.8 L/kg in the double-drug group and 1.3 +/- 0.8 L/kg in the triple-drug group (p > 0.05). Plasma half-life ranged from 1.7 to 4.3 h (mean 2.7) in the double-drug group versus 1.4 to 3.4 h (mean 2.6) in the triple-drug group (p > 0.05).

CONCLUSIONS

These data indicate that cyclosporine had no definitive influence on methylprednisolone disposition. The results reveal a wide variation in methylprednisolone metabolism in renal transplant recipients receiving either a double- or triple-drug immunosuppressive regimen. Typically, methylprednisolone is prescribed according to a standardized dosing protocol that assumes minimal interpatient variation. Therefore, the pharmacokinetic variability noted in this study may have important clinical implications regarding the development of chronic toxicity (e.g., osteoporosis, hypothalamic-pituitary-adrenal suppression) and the attainment of successful immunosuppression.

Increased peripheral resistance during reduced uterine perfusion pressure hypertension in pregnant rabbits

The role of an increase in total peripheral resistance (TPR) and the contribution of angiotensin II (ANG II) to the hypertension induced by reduced uterine perfusion pressure (RUPP) was explored in pregnant rabbits. On the 22nd day of gestation, a catheter and a microthermocouple were placed in the aorta to measure mean arterial pressure (MAP) and cardiac output (CO), respectively. Three days later, RUPP was induced by a clip on the aorta proximal to the ovarian and distal to the renal arteries. Mean arterial pressure distal to the clip (uterine perfusion pressure) was reduced to 56 +/- 8% (mean +/- SD) of the initial level. Twenty-four hours later, MAP rose from 65 +/- 3 to 84 +/- 11 mm Hg; CO index decreased from 207 +/- 18 to 169 +/- 27 ml/min/kg; and TPR index increased from 0.32 +/- 0.03 to 0.51 +/- 0.08 mm Hg kg/ml/min, respectively (n = 7, all p less than 0.01). Sham-operated pregnant rabbits (n = 7) and non-P rabbits (n = 5) with a comparable distal aortic pressure reduction experienced no change in MAP or CO. Infusion of a receptor antagonist of angiotensin II (Sar1,Ile8-Ang II, 1 microgram/kg/min for 20 min) decreased MAP in sham-operated pregnant rabbits from 64 +/- 6 to 54 +/- 6 mm Hg (p less than 0.01) but did not change MAP in RUPP hypertensive rabbits (86 +/- 9 mm Hg before and 87 +/- 8 at the end of infusion, n = 6). These data indicate that RUPP in pregnant rabbits leads to a high resistance form of hypertension in which the formation of Ang II is not increased.

Renal blood flow response to angiotensin II infusions in conscious pregnant rabbits

Renal blood flow (RBF) was measured in conscious rabbits while nonpregnant and during pregnancy using chronically implanted ultrasonic transit-time flow probes. The effects of the cyclooxygenase inhibitor meclofenamate (5 mg/kg) and the angiotensin-converting-enzyme inhibitor captopril (5 mg/kg) on basal RBF and on RBF responses to systemic angiotensin II infusions (2.5-80 ng.kg-1.min-1) were determined. Basal RBF declined (P less than 0.001 to P less than 0.005) with meclofenamate by 9-16% in pregnant (n = 7) and by 10% in nonpregnant (n = 7) rabbits. Captopril increased (P less than 0.05 to P less than 0.01) RBF by 9-11% in pregnant (n = 5) and by 12% in nonpregnant (n = 5) rabbits. There was no effect of the vehicle (normal saline) on RBF. The reduction in RBF (% from baseline) in response to infused angiotensin II was attenuated in pregnant compared with nonpregnant rabbits. Pretreatment with meclofenamate enhanced the renal vasoconstrictor action of angiotensin II in a similar fashion in both pregnant and nonpregnant rabbits. Captopril or saline did not alter the RBF responses to angiotensin II infusions. Mean arterial pressure was lower in pregnant (78 +/- 3 mmHg, n = 7) vs. nonpregnant (88 +/- 5 mmHg, n = 10) rabbits, suggesting lower total peripheral resistance. The data indicate 1) chronically implanted ultrasonic flow probes can be an effective tool for monitoring RBF in conscious rabbits, 2) prostaglandins and the renin-angiotensin system influence basal RBF in conscious rabbits, and 3) the renal vasoconstrictor effect of angiotensin II is blunted in pregnant rabbits and this attenuated response appears to be independent of prostaglandins.