Intra-individual consistency of prednisolone kinetics during long-term prednisone treatment

Monitoring prednisolone and prednisone in saliva: a population pharmacokinetic approach in healthy volunteers

BACKGROUND

Prednisolone (PLN) is a widely used corticosteroid in a variety of immune-mediated diseases. Treatment regimes generally consist of empirically derived treatment doses, whereas therapeutic response among patients is highly variable. Drug monitoring of serum PLN levels might support a more rational approach to dose selection, yet is invasive and laborious. In analogy to cortisol, salivary PLN may offer a good alternative for serum PLN, being a representative approximation of free serum PLN. The aims of this study were to evaluate the correlation between free serum and salivary PLN levels and to quantify this relationship within a population pharmacokinetic model.

METHODS

PLN and prednisone (PN) concentrations were measured in 396 samples from 19 healthy volunteers after oral ingestion of 80 mg PLN. Measurements in serum, ultrafiltrate, and saliva were performed with a recently validated liquid chromatography tandem mass spectrometry method. Population pharmacokinetic analysis was performed with nonlinear mixed effect modeling using NONMEM.

RESULTS

Salivary PLN levels correlated well with free serum PLN levels (r = 0.931, P < 0.01). A weaker correlation was found for PN (r = 0.318, P < 0.01), which may be explained by the finding that salivary PN levels mainly seemed to consist of PLN enzymatically converted to PN. Total and free serum PLN concentrations decreased over time after drug administration and showed a nonlinear mutual relationship, consistent with concentration-dependent protein binding. Modeled PLN pharmacokinetics corresponded with previous reports. Low to moderate interindividual variability was found for V/F and CL/F (coefficients of variation were 13.8% and 14.6%, respectively). Free and salivary PLN showed a nonlinear relationship with total PLN. An equation predicting free serum levels from salivary levels was successfully derived from the data.

CONCLUSIONS

This study is the first to describe the relationship between salivary and (free) serum PLN using a population pharmacokinetic model. Salivary PLN was found to be a reliable predictor of free and total serum PLN in healthy volunteers. The results of this study encourage further exploration of the use of saliva as a noninvasive and feasible method for drug monitoring of PLN.

Population pharmacokinetics of prednisolone in children with acute lymphoblastic leukemia

PURPOSE

To evaluate the plasma protein binding and pharmacokinetics of prednisolone during therapeutic use in children with acute lymphoblastic leukemia (ALL) using the population approach.

METHODS

A two-compartment pharmacokinetic model was used to describe data from 23 children with ALL (aged 2-15 years). Prednisolone (60 mg/m(2) per day in three divided doses) was administered both orally and intravenously, and samples were obtained on several days during the initial 5 weeks of remission induction therapy. Unbound plasma concentrations ( n=288) were determined by HPLC and ultrafiltration. Nonlinear mixed-effects modeling (WinNonMix version 2.0.1) was used to estimate the pharmacokinetic parameters, to identify significant covariates, and to estimate the protein binding parameters.

RESULTS

Prednisolone showed complete oral bioavailability. The median unbound clearance (32 l/h per m(2)) was lower, and the half-life (3.6 h) longer than previously reported in childhood ALL. Body weight was a significant covariate for the central and peripheral volumes of distribution resulting in interindividual variabilities of 50% and 42%. Including body surface area as a covariate for clearance decreased the interindividual variability to 14%. The estimated areas under the unbound plasma concentration-time curves showed less than twofold variation among patients, and a residual variability of 20% indicated that the pharmacokinetic parameters remained stable during induction therapy. The estimated protein binding parameters were comparable to, but slightly lower than, previously published values and independent of the albumin concentration.

CONCLUSIONS

The study showed complete oral bioavailability, a lower unbound clearance and a longer half-life for prednisolone than previously reported in childhood ALL. Plasma protein binding was independent of the albumin concentration. Due to the small inter- and intraindividual variations in the pharmacokinetic parameters, body surface area-based dosing is sufficient to obtain similar systemic exposure among patients.

Pharmacokinetics of prednisolone during administration of sirolimus in patients with renal transplants

The pharmacokinetic interaction of multiple oral doses of sirolimus (rapamycin) and prednisone were evaluated in 40 stable patients with renal transplants receiving concomitant multiple doses of cyclosporine. Nine sirolimus dosage levels from 1 mg/m2/day to 13 mg/m2/day were studied and compared with placebo. Plasma concentrations of prednisone, prednisolone, and cortisol were measured by high-performance liquid chromatography and analyzed by noncompartmental methods. Mean pharmacokinetic values of prednisolone found before sirolimus administration were as follows: peak plasma concentration (Cmax) was 187 ng/mL; time to peak plasma concentration (tmax) was 2.03 hours; rate of reaching peak plasma concentration (Cmax divided by the area under the concentration-time curve [AUC]) was 0.149 hour-1; terminal half-life (t1/2) was 3.60 hours; AUC was 1206 ng.hour/mL; and apparent clearance (Cl/F) was 0.094 L/hour/kg. During the 2 weeks of concomitant administration, prednisolone elimination decreased in relation to sirolimus dosages. These changes were modest, with mean increases of 18% in Cmax and 27% in t1/2 and mean decreases of 27% in Cl/F for the groups receiving 6 mg/m2/day to 13 mg/m2/day. Most patients initially had plasma cortisol concentrations indicative of adrenal suppression. With sirolimus treatment, the Cmax of cortisol did not decrease further, but the AUC (8:00 AM-8:00 PM) values were significantly lower, independent of sirolimus exposure. The AUC for cyclosporine did not correlate with sirolimus and prednisolone exposure. A 2-week course of sirolimus showed a slight pharmacokinetic interaction between sirolimus and prednisolone/prednisone/cortisol in stable patients with renal transplants.

Increased hepatic urea synthesis in patients with active inflammatory bowel disease

BACKGROUND/METHODS

Patients with active inflammatory bowel disease are often reported to be in negative nitrogen balance. Therefore, we examined basal and amino acid stimulated urea synthesis in 11 patients with active inflammatory bowel disease (six with Crohn's disease and five with ulcerative colitis) and in 10 patients with non-active disease (six with Crohn's disease and four with ulcerative colitis). A primed continuous infusion of an amino acid mixture was given from t = 1 h to t = 5 h; during the first and the last 2 h no amino acid infusion was given. Urea nitrogen synthesis rate was calculated in hourly intervals for 7 consecutive hours. Urea nitrogen synthesis rate was quantified independent of changes in blood amino acid concentration by means of the functional hepatic nitrogen clearance, i.e. the linear slope of the regression of urea nitrogen synthesis rate of blood amino acid concentration.

RESULTS

Basal urea nitrogen synthesis rate was 24.5 +/- 2.9 mmol/h in the patients with no disease activity and 43.8 +/- 2.2 mmol/h in patients with active disease (p < 0.01). During amino acid infusion urea nitrogen synthesis rate was elevated two-fold in the patients with active disease. Functional hepatic nitrogen clearance was 28.2 +/- 1.5 1/h in patients with no disease activity and 56.1 +/- 4.1 1/h in patients with active disease (p < 0.01). No differences between the two groups were observed as regards basal or stimulated plasma glucagon and cortisol and serum levels of interleukin-1 alpha, interleukin-1 beta, tumor necrosis factor alpha and interleukin-6.

CONCLUSIONS

The results show that the liver function related to conversion of amino-nitrogen to urea is increased in patients with active inflammatory bowel disease. No differences among known and possible regulators of urea synthesis were found between the two groups. The accelerated hepatic amino-nitrogen conversion contributes to the less efficient nitrogen economy in patients with active inflammatory bowel disease.

Somatostatin prevents the postoperative increases in plasma amino acid clearance and urea synthesis after elective cholecystectomy

The importance of glucagon on postoperative changes in hepatic amino-nitrogen conversion were investigated in six patients undergoing elective cholecystectomy for uncomplicated gall stones. Patients were given infusions of somatostatin (bolus of 6 micrograms/kg followed by continuous infusion of 6 micrograms/kg/h) from induction of anaesthesia to the end of investigation, the first postoperative day (30 hours). Controls were 16 patients undergoing the same procedures omitting the somatostatin infusion. In all patients blood concentration and plasma clearance of total alpha-amino-nitrogen, and amino acid stimulated rate of urea synthesis were measured. Elective cholecystectomy decreased blood alpha-amino-nitrogen concentration from mean (SEM) 2.9 (0.2) to 2.4 (0.1) mmol/l (p < 0.05), increased the clearance of total alpha-amino-nitrogen from 5.2 (0.3) to 6.6 (0.3) ml/s (p < 0.05), and increased the rate of amino acid stimulated urea synthesis from 27 (1) to 37 (2) mumol/s (p < 0.05) pointing to increased hepatic removal of amino-nitrogen at expense of plasma amino-nitrogen. Infusion of somatostatin prevented increase of glucagon for 24 hours after surgery, and prevented the negative changes in postoperative nitrogen homeostasis resulting from the postoperative changes in hepatic nitrogen conversion, suggesting glucagon as mediator. The exact mechanism remains in doubt, however, because of the multiple effects of somatostatin.

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.

Metabolism of prednisone in kidney transplanted patients with necrosis of the femoral head

Interindividual variation of the metabolism of prednisolone and of the susceptibility to glucocorticoids might be possible factors contributing to the development of osteonecrosis after renal allotransplantation. As this aspect has not been properly investigated previously, we compared, in the present study, the metabolism of total and free prednisolone in 6 renal allotransplanted patients who subsequently developed osteonecrosis of the femoral head and the metabolism of 6 matched controls, who did not develop osteonecrosis. There was no difference in age, bodyweight, total serum protein or albumin, or in liver or renal function. The baseline cortisol was 54 +/- 23 micrograms in patients with necrosis, and 102 +/- 53 micrograms/l in patients without necrosis (n.s.). Likewise there was no difference in the peak concentration of prednisolone (420 +/- 43 vs. 394 +/- 42 micrograms/l, n.s.), the bioavailability (0.57 +/- 0.09 vs. 0.61 +/- 0.05, n.s.) or in the apparent volume of distribution at steady state (Vdss, 0.37 +/- 0.09 vs. 0.37 +/- 0.04 l/kg, n.s.). The clearance of prednisolone in patients with osteonecrosis was 33% lower (0.79 +/- 0.11 vs. 1.18 +/- 0.13 ml/min./kg b.wt., P < 0.05) and t1/2 was correspondingly 33% longer (246 +/- 18 min. vs. 184 +/- 15 min., P < 0.05) than in patients without osteonecrosis. However, there was no difference in the apparent volume of distribution of free prednisolone (2.07 +/- 0.36 vs. 1.69 +/- 0.28 l/kg, n.s.), in the t1/2 (152 +/- 30 vs. 107 +/- 20 min., n.s.), or in the clearance (7.33 +/- 2.12 vs. 7.82 +/- 1.18 ml/min./kg) between the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Autonomic nervous system function in patients with functional abdominal pain. An experimental study

Functional abdominal pain--that is, pain without demonstrable organic abnormalities--has often been associated with psychologic stress. The aim of the present study was to investigate whether sympathetic nervous system response to laboratory stress and basal parasympathetic neural activity were disturbed in 22 patients with functional abdominal pain (functional group) as compared with 14 healthy controls (healthy group) and 26 patients with organic abdominal pain (organic group) due to duodenal ulcer (DU), gallstones, or urinary tract calculi. Plasma adrenocorticotrophic hormone (ACTH) and serum cortisol measurements were included, to assess the pituitary-adrenocortical axis. Heart rate, systolic blood pressure, and plasma adrenaline increased significantly in all groups in response to a stress test (mental arithmetic). Plasma noradrenaline increased in the DU patients only, and plasma ACTH and serum cortisol did not increase at all in any of the groups. As a measure of parasympathetic neural activity, independent of sympathetic neural activity, the beat-to-beat variation of the heart rate was calculated. The functional patients had a significantly higher beat-to-beat variation expressed as the mean square successive differences of the R-R intervals (MSSD), indicating a higher basal parasympathetic neural activity (mean MSSD +/- SEM = 64 +/- 6 msec in the functional group, 46 +/- 6 msec in the healthy group, and 49 +/- 6 msec in the organic group; P = 0.03). A reduced sympathetic neural response as indicated by a lesser stress-induced increment in heart rate, was seen in both patient groups (functional, 13 +/- 2 beats/min; organic, 10 +/- 2 beats/min) as compared with the healthy group (19 +/- 2 beats/min; P = 0.003).(ABSTRACT TRUNCATED AT 250 WORDS)

Elective cholecystectomy increases plasma amino-acid clearance and hepatic capacity for urea synthesis for one week

The importance of the liver in post-operative catabolism was studied in 6 cholecystectomy patients given a mixture of amino-acids as prime-continuous infusionś pre-operatively and on the 1st, 3rd, 6th and 12th post-operative day. The plasma clearance of total alpha-amino-nitrogen and of single amino-acids, the urea-nitrogen synthesis rate, and the functional hepatic nitrogen clearance were calculated. Surgery decreased fasting blood amino-nitrogen concentration by 15% (p < 0.01), and increased the plasma clearance of amino-nitrogen by 30% (P < 0.05) on the 1st, 3rd and 6th post-operative day. Surgery doubled the functional hepatic nitrogen clearance (p < 0.01) on the 1st, 3rd and 6th post-operative day. This indicates that post-operative stress catabolism is partly due to a hepatic condition by which the liver eliminates more amino-nitrogen despite lower amino-acid concentration in the blood, for one week post-operatively.

Autonomic response to an experimental psychological stressor in healthy subjects: measurement of sympathetic, parasympathetic, and pituitary-adrenal parameters: test-retest reliability

A mental arithmetic test (the stressor; 15 min) significantly increased systolic and diastolic blood pressure, heart rate and plasma adrenaline by 11%, 12%, 28% and 152% respectively, with a prompt return to resting values after the test. Plasma noradrenaline and serum cortisol did not increase significantly during the 15 min of stress. Afterwards, however, the concentrations of both hormones increased, resulting in a total and significant increase averaging 19% and 23%, respectively. Plasma adrenocorticotrophic hormone (ACTH) did not rise significantly, but it was only measured before and at the end of the stressor. As a measure of parasympathetic nervous function, the beat-to-beat variation of heart rate, expressed as the mean successive square difference (MSSD), was employed. Four to 14 months later, the investigation was repeated, and resting values of all measures were found to be stable. The increments in systolic blood pressure and heart rate were significantly lower at retest. MSSD at stress, but not at rest, was significantly lower at retest. The mental arithmetic stress test as described here produces a sufficient autonomic response to make it viable for laboratory stress research. However, if repeated examinations are desired, the lower response at retest should be taken into consideration.

Basal and stimulated elastolytic activity of blood monocytes is increased in glucocorticoid-treated giant cell arteritis

The elastolytic capacity of live human blood monocytes was studied in patients with giant cell arteritis (GA) and in age-matched controls. Despite normalized acute-phase reactants during glucocorticoid (GC) therapy, the basic activity of monocytes from patients with newly diagnosed GA was elevated compared with controls (80 vs. 39 ng/h, p less than or equal to 0.01). The maximum response was enhanced by stimulation with immune complexes (224 vs. 125 ng/h, p less than or equal to 0.01) and with phorbol myristic acetate (324 vs. 214 ng/h, p less than or equal to 0.01). No age difference was found between healthy young and old people. Cell surface related human monocyte elastolytic activity could act as a sensitive marker of cell activation in vivo.

Effect of prior immobilization on muscular glucose clearance in resting and running rats

In vitro studies have shown that prior disuse impairs the glucose clearance of red skeletal muscle because of a developed insensitivity to insulin. We studied whether an impaired glucose clearance is present in vivo in 42-h immobilized muscles of resting rats and, furthermore, whether the exercise-induced increase in glucose clearance of red muscles is affected by prior immobilization. The 2-[3H]deoxy-D-glucose (2DG) bolus injection method was used to determine glucose clearance of individual muscles. At rest, glucose clearance was markedly impaired in rats with previously immobilized red muscles compared with nonimmobilized control rats (red gastrocnemius 0.46 +/- 0.02 vs. 0.99 +/- 0.08 and soleus 1.10 +/- 0.30 vs. 3.97 +/- 0.54 ml.min-1.100 g-1, P less than 0.005). During running (18 m/min), glucose clearance did not differ between muscles in previously immobilized and control rats. Insulin levels were always similar in the two groups and decreased during exercise. Intracellular nonphosphorylated 2DG was present in tissues with high glucose clearances. In conclusions, 42 h of immobilization markedly impairs glucose clearance of resting red muscle fibers in vivo. Apparently, physical inactivity in particular affects steps involved in insulin-mediated action that are not part of contraction-induced glucose uptake and metabolism. Presence of intracellular 2DG shows that separate determination of phosphorylated 2DG is necessary for accurate estimates of glucose metabolism and that accumulation of phosphorylated 2DG does not accurately reflect glucose transport.

Glucocorticoid levels and lymphocyte functions in kidney transplanted patients

The in vitro lymphocyte response to mitogen stimulation and the in vitro lymphocyte sensitivity to glucocorticoid were examined in 72 kidney transplanted patients before and after administration of high or low doses of glucocorticoid. Administration of 10 mg of prednisone orally to 10 patients did not significantly change the mitogen responses or the lymphocyte sensitivity to methylprednisolone. Likewise, administration of 100-120 mg of methylprednisolone, intravenously to 62 patients did not significantly affect the mitogen responses, but, in contrast, the lymphocyte sensitivity to the immunosuppressive effect of methylprednisolone was clearly increased. This effect was highly significant in both cyclosporine A and azathioprine treated patients. These findings suggest that a change of the lymphocyte sensitivity to the immunosuppressive effect of methylprednisolone may occur after a high dose of glucocorticoid, anaesthesia and surgery, although no changes of the immunefunctions in vitro can be demonstrated by examining the mitogen response of the lymphocyte cultures. No relationship was found in the present study between the individual lymphocyte sensitivity to glucocorticoid and metabolic clearance rate.