Dose-dependent pharmacokinetics of prednisone and prednisolone in man

Pharmacokinetics of Oral Prednisone at Various Doses in Dogs: Preliminary Findings Using a Naïve Pooled-Data Approach

This pilot study aimed to determine the plasma pharmacokinetics of prednisone and its active metabolite prednisolone following oral prednisone administration in dogs-using dosing regimens that cover anti-inflammatory to immuno-suppressive biological effects. Six healthy Beagle dogs were given 0.5, 1, 2, and 4 mg/kg prednisone orally once daily for 5 days, each successive course separated by a washout period of 9 days. At steady-state (Day 4), a sparse sampling design allowed for collection of blood from 2/6 individuals for each of the following time points: 0, 15, 30, 60, 90, 120, 240, 480, and 720 min. Prednisone and prednisolone were quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Oral prednisone was rapidly converted to prednisolone in dogs (≤ 30 min), with plasma prednisolone reaching ~6-fold greater levels (0-656.1 ng/mL) than prednisone (0-98.8 ng/mL) overall. The ratio of plasma prednisolone/prednisone was constant across the dosing regimens, indicating a non-saturation of the hepatic 11-β-hydroxysteroid dehydrogenase that converts the prodrug to the active metabolite in dogs. The level of both corticosteroids increased with increasing dosing regimens, albeit in a non-linear manner. Non-compartmental pharmacokinetic parameters are described, including peak concentration (C_max), time of peak concentration (T_max), area under the concentration-time curve (AUC_last), and the elimination half-life (t _1/2) for both corticosteroids, as well as clearance and volume of distribution during the terminal phase (V_z) for the administered drug (prednisone). In sum, the present study utilizes a sparse sampling and naïve pooled-data approach to estimate pharmacokinetic parameters for prednisone and prednisolone, providing supporting preliminary knowledge that can be used to optimize corticosteroid efficacy and minimize toxicity in canine patients.

Biowaiver monographs for immediate release solid oral dosage forms: prednisone

Literature data relevant to the decision to allow a waiver of in vivo bioequivalence (BE) testing for the approval of immediate release (IR) solid oral dosage forms containing prednisone are reviewed. Due to insufficient data prednisone cannot be definitively classified according to the current Biopharmaceutics Classification System (BCS) criteria as both the solubility and the permeability of prednisone are on the borderline of the present criteria of BCS Class I. Prednisone's therapeutic indications and therapeutic index, pharmacokinetics and the possibility of excipient interactions were also taken into consideration. Available evidence indicates that a biowaiver for IR solid oral dosage forms formulated with the excipients tabulated in this article would be unlikely to expose patients to undue risks.

Biowaiver monographs for immediate release solid oral dosage forms: prednisolone

Literature data relevant to the decision to allow a waiver of in vivo bioequivalence (BE) testing for the approval of immediate release (IR) solid oral dosage forms containing prednisolone are reviewed. Data on its solubility, oral absorption, and permeability are not totally conclusive, but strongly suggest a BCS Class 1 classification. Prednisolone's therapeutic indications and therapeutic index, pharmacokinetics, and the possibility of excipient interactions were also taken into consideration. Available evidence indicates that a biowaiver for IR solid oral dosage forms formulated with the excipients tabulated in this article would be unlikely to expose patients to undue risks.

Glucocorticoid pharmacokinetics and growth retardation in children with renal transplants

Long-term glucocorticoid treatment contributes to the growth retardation in children after renal transplantation. We investigated whether determination of prednisone (PN) and prednisolone (PL) in plasma and PN, PL, and 6-beta-hydroxyprednisolone (betaOH-PL) in urine could help to predict growth. PN and PL pharmacokinetics were studied in 36 children, from 5 to 15 years of age, receiving daily (D) or alternate-day (AD) oral PN treatment. Statural growth velocity was evaluated over a 1-year period. We compared three groups of children according to the growth kinetics during the study year (catch-up, stable, or decline) for clinical and pharmacokinetic parameters. A multiple linear regression analysis was performed in order to determine pharmacokinetic parameters able to explain height 1 year after inclusion. Height at the beginning of the study, creatinine clearance, and type of D or AD treatment explained 94.2% of height variance 1 year after inclusion. Only PL clearance was associated with growth evolution, but introduction of PL clearance in the multivariate model did not improve the variance of height accounted for by the previous model. We, therefore, do not recommend using glucocorticoid pharmacokinetics to predict growth retardation in children with renal transplantation.

Disposition of prednisone and prednisolone in the perfused rabbit liver: modeling hepatic metabolic processes

The livers of 15 rabbits were perfused in situ with prednisone (PO) or prednisolone (POH) over a wide range of steady state concentrations, resulting in multiple experimental measurements per organ. Linearity of extraction, an apparent lack of oxidative conversion, and marked preference for the reduction of PO to POH was observed. Predictions of hepatic tissue concentrations were made using both the well-stirred and parallel-tube model approximations. Glucocorticoid disposition across the liver was described by a series of differential equations. Discrimination between the two models was accomplished by examining the effects of changes in flow rate upon the availability of the highly extracted drug PO. The well-stirred model very closely predicted the observed changes in availability of PO, whereas the parallel-tube model provided poor predictions. The intrinsic clearances of interconversion and elimination of PO and POH were subsequently calculated by population analysis using NONMEM. This method assumed the well-stirred model and resulted in intrinsic clearance estimates of 26 ml/min for the elimination of POH, 157 ml/min for reductive conversion of PO to POH, and 205 ml/min for the irreversible elimination of PO. A mechanism of intrahepatic disposition of these glucocorticoids was proposed using well-stirred model predictions of hepatic drug concentrations, the perfusion rate limitation to drug transport, and the assumption of no oxidative interconversion of POH to PO. In this case, the capacity for reduction of PO to POH approaches the elimination clearance of PO and the elimination of PO is about 13 times greater than the elimination clearance of POH.

Prednisone and prednisolone interconversion in the rabbit utilizing unbound concentrations

Prednisolone (POH) and prednisone (PO) were both administered via seven different intravenous infusions (three POH and four PO) in each of six rabbits to obtain steady state. Bolus doses of POH and PO were also administered to four of the rabbits. Plasma samples of POH and PO were analyzed by normal phase HPLC. Unbound concentrations of both compounds were estimated in each rabbit using equilibrium dialysis and computer fit of the nonlinear or linear binding. The unbound fraction of POH ranged between 3 and 15 per cent from tracer to total concentrations of 2000 micrograms-1. The unbound fraction of PO ranged between 23 and 34 per cent and appeared nonlinear for four of the rabbits. The mean apparent unbound clearances of POH ranged from 4.4 to 6.1 lh-1kg-1 and from 4.1 to 5.9 lh-1kg-1 for PO, and were dose-independent for both compounds. The available fraction of POH from PO was 50 to 70 per cent and independent of dose. The available fraction of PO from POH averaged 44 per cent at the low infusion rate decreasing to 16 and 20 per cent at the medium and high infusion rates. Although saturability in the formation of PO from POH was noted, this nonlinear step is apparently not large enough to induce observable changes from linearity in the overall disposition of unbound POH.

Prednisolone binding to plasma proteins in domestic species

The binding of prednisolone to total plasma proteins of dogs, horses, cows, and sheep was characterized using equilibrium dialysis. Prednisolone was bound to a first protein with high affinity but low capacity (transcortin) and to a second protein according to a nonsaturable mechanism (albumin). Interspecies differences were observed, with cows and dogs exhibiting the lowest, and sheep and horses the highest specific binding capacities. The results are in good agreement with known pharmacokinetic properties of prednisolone in domestic species.

The non-linear pharmacokinetics of prednisone and prednisolone. III. Experiments using the rabbit as an animal model

Intravenous zero order infusions were administered to New Zealand white rabbits. In a pilot study using one rabbit, prednisone and prednisolone clearance values increased with increase in either prednisone or prednisolone infusion rates. In the second study, prednisone was infused until both prednisone and prednisolone achieved steady-state concentrations. In the third study, prednisone was infused until only prednisone achieved steady-state concentrations. The results of the three experiments support the use of a non-linear reversible metabolism model to describe the pharmacokinetic relationship between prednisone and prednisolone.

Relative and absolute bioavailability of prednisone and prednisolone after separate oral and intravenous doses

A randomized, four-way cross-over study was conducted in eight healthy male volunteers to determine the relative and absolute bioavailability of prednisone (PN) and prednisolone (PL). PN and PL were administered as single, oral 10-mg tablet doses and as 10-mg zero-order 0.5-hour intravenous infusions. Comparable mean PN and PL maximum plasma concentrations (Cmax), times for Cmax, areas under the plasma concentration-time curves (AUC), and apparent elimination rate constants between tablet treatments demonstrated that PN and PL tablets were bioequivalent. Absolute bioavailability (F) determinations based on plasma PL concentrations were independent of which IV treatment was used as reference and indicated complete systemic availability of PL from both PN and PL tablets. However, F based on plasma PN data was contradictory. Using IV PN as reference, approximately 70% systemic availability was observed from both tablets, whereas using IV PL as reference, systemic availability was greater than unity. PN and PL are model compounds that exemplify the difficulties involved in accurately determining the relative and absolute bioavailability of substances that undergo reversible metabolism.

The nonlinear pharmacokinetics of prednisone and prednisolone. II. Plasma protein binding of prednisone and prednisolone in rabbit and human plasma

The protein binding characteristics of prednisone and prednisolone were determined in human and rabbit plasma and in a 4.7 per cent human serum albumin (HSA) solution. The influence of prednisolone on prednisone binding in human plasma was also examined. Prednisolone exhibited nonlinear binding and prednisone linear binding characteristics in both human and rabbit plasma. Prednisone binding was not influenced by the presence of prednisolone. Prednisone binding to HSA was linear but to a degree substantially lower than observed in human plasma, suggesting the possibility that prednisone binds to other proteins in human plasma. The results support the hypothesis that the protein binding characteristics of prednisone and prednisolone do not explain the reported nonlinear pharmacokinetics of prednisone.

The non-linear pharmacokinetics of prednisone and prednisolone. I. Theoretical

Three simple linear and three simple non-linear pharmacokinetic models are presented which incorporate the reversible metabolism that occurs between prednisone and prednisolone. Under steady-state conditions it is possible to not only distinguish between the linear and non-linear models but also to determine which particular model of each group applies to a given set of data. While the non-linear conversion of prednisolone to prednisone is important in explaining the pharmacokinetics of prednisone in all three non-linear models, the same is not true for prednisolone.

Pharmacokinetics of prednisolone after high doses of prednisolone hemisuccinate

Prednisolone in the form of its hemisuccinate was given intravenously in two different doses (1200 mg and 75 mg). Plasma levels of the ester and prednisolone were measured and pharmacokinetic parameters were calculated. The results indicate a dose-dependency in the pharmacokinetics of both hemisuccinate and the free alcohol. For the high dose 8 per cent of the administered ester was found unchanged in the urine indicating incomplete conversion of the pro-drug. Comparison with previous studies leads to the conclusion that prednisolone shows doubled non-linear pharmacokinetics with higher total body clearance in the medium dose range than in the low and high dose range. Volume of distribution changes accordingly, but overall elimination rate remains remarkably constant. Saliva levels of prednisolone were low and agree reasonably well with calculated plasma concentrations of free, non-protein-bound prednisolone. No prednisolone hemisuccinate was found in saliva.

Nasal bioavailability and systemic effects of the glucocorticoid budesonide in man

Budesonide, a topically potent glucocorticoid, was administered to 4 healthy volunteers by i.v. infusion and by nasal instillation of 100 micrograms tritium-labelled drug. Plasma was analyzed by liquid chromatography plus scintillation counting of collected fractions. After i.v. administration the plasma clearance was 0.921/min and the apparent volume of distribution was 2.81/kg. After nasal administration, the time to reach the peak plasma level was approximately 30 min, and the systemic availability was 102%. Budesonide had marginal effects on plasma cortisol and white blood cell counts either after i.v. or nasal administration. Thus, nasally instilled budesonide in solution is rapidly and completely absorbed from the nasal mucosa. The systemic effects after this clinically recommended nasal dose were negligible.

Pharmacological aspects of corticosteroid pulse therapy

Pulse corticosteroid therapy involves intravenous administration of "suprapharmacological" doses (0.5-2 g) of prednisolone or its equivalents. This dose is usually given on three consecutive days and possibly once a month thereafter. The pharmacological effects of the single pulse dose lasted for about two days. Whether these effects differ quantitatively or qualitatively from the effects of the smaller, conventional doses is unclear at present. The usual side-effects of glucocorticoid therapy may occur with pulse therapy but evidently less frequently than with conventional modes of steroid therapy.

Pharmacokinetics and protein binding of prednisolone after oral and intravenous administration

The pharmacokinetics of prednisolone after oral and intravenous administration of 10 and 20 mg have been studied. Serum protein binding of prednisolone was also measured after the i.v. injections. The bioavailability after oral administration was 84.5% after 10 mg and 77.6% after 20 mg (p greater than 0.05). Dose dependent pharmacokinetics were found, the VDss and Clt being significantly larger (p less than 0.01) after 20 mg i.v. than after 10 mg i.v. The protein binding of prednisolone in all subjects was non-linear, and is the most likely cause of the dose dependent pharmacokinetics, as there was no dose dependent variation in elimination half-time.

Dose dependent pharmacokinetics of prednisone and prednisolone in man

Six healthy male volunteers were given 5, 20, and 50 mg of oral prednisone and 5, 20, and 400 mg doses of intravenous prednisolone. Plasma and urine concentrations of prednisone and prednisolone were determined by HPLC, and the binding of prednisolone to plasma proteins was measured by radioisotopic and equilibrium dialysis techniques. The pharmacokinetics of both oral prednisone and intravenous prednisolone were dose-dependent. The mean oral dose plasma clearances of prednisone ranged from 572 ml/min/1.73 m 2 for the 5 mg dose to 2271 ml/min/1.73 m 2 for the 50 mg dose. Changes in prednisone half-life were insignificant, but increases in the half-life of its metabolite were dose-dependent. The systemic plasma clearance of i.v. prednisolone was dose-dependent and increased from 111 to 194 ml/min/1.73 m 2 over the 5 to 40 mg i.v. dosage range. The steady-state volume of distribution also increased, but little change in mean transit time and half-life was found. The binding of prednisolone to plasma proteins was markedly concentration-dependent, and a two compartment, nonlinear equation was used to characterize the effective binding of prednisolone to transcortin and albumin. The apparent pharmacokinetic parameters of protein-free and transcortin-free prednisolone were relatively constant with dose. The interconversion of prednisone and prednisolone varied with time and dose, although prednisolone concentrations dominated by 4- to 10-fold over prednisone. In urine, 2-5% of either administered drug was excreted as prednisone and 11-24% as prednisolone. The apparent renal clearances of both steroids were also nonlinear and unrelated to protein binding. These studies indicate that the pharmacokinetics of prednisone and prednisolone are dose-dependent and that protein binding does not fully explain their apparent nonlinear distribution and disposition.

Pharmacokinetic evaluation of betamethasone and its water soluble phosphate ester in humans

Two betamethasone tablet formulations, and betamethasone phosphate solution were compared in a plasma level study. The tablet formulations (A and B) and a solution of betamethasone phosphate (C) were administered in single 2 mg doses to nine volunteers according to a three times repeated Latin square design. Plasma samples were obtained over 72 h following each dose and plasma was analysed for betamethasone by radioimmunoassay. Pharmacokinetic evaluation of the data, obtained according to the one-compartment open model, indicated that there were no significant differences between the extent of absorption, and the first-order elimination rate constants. As would be expected, the solution (C) gave a faster absorption rate than tablets A and B.

Pharmacokinetics of prednisolone in normal and asthmatic subjects in relation to dose

The pharmacokinetics of prednisolone have been studied in asthmatic patients following intravenous injection at three different doses and in normal volunteers at five oral doses. Plasma prednisolone concentrations were measured by radioimmunoassay. With increasing dose there is an increase in the apparent volume of distribution, plasma clearance and half life. The relationship between area under the plasma concentration time curve, maximum concentration and dose is linear but the regression lines do not pass through the origin. These findings following oral and intravenous administration confirm that prednisolone shows non-linear kinetics.

Pharmacokinetics of intravenous and oral prednisolone

1 Doses of 16, 32, 48 and 64 mg prednisolone were administered intravenously to normal volunteers who also received 100 prednisolone orally. Plasma prednisolone concentrations were estimated by quantitative thin layer chromatography. 2 The bioavailability fraction was 1.063 +/- 0.154 (s.d.) indicating complete availability of prednisolone following oral administration. 3 The mean T 1/2 over all doses were 4.11 +/- 0.97 (s.d.) h and there was no evidence of a dose-related change in its value. 4 The mean systemic clearance over all doses was 0.104 +/- 0.034 (s.d) 1 h-1 kg-1. There was no evidence of a dose-related change in clearance or in the apparent volume of distribution (overall mean 0.588 +/- 0.152 1 kg-1). 5 The area under the plasma concentration-time curve was linearly related to dose. 6 Plasma concentration-time curves normalised for dose were superimposable. 7 It was concluded that over the dose range investigated, non-linear pharmacokinetic behaviour had not been demonstrated in this group of normal volunteers.

Pharmacokinetics and bioavailability of prednisone and prednisolone in healthy volunteers and patients: a review

Limited information is available on the pharmacokinetics and bioavailability of prednisone and prednisolone in patients with different disease states. This is partly due to difficulty in measuring these drugs in biological fluids at the usual dosages prescribed to patients. This article attempts to comprehensively review these studies categorized under the following four sections: (1) bioavailability--healthy volunteers, patients with respiratory disease, patients with liver disease, patients with kidney disease, pediatric patients with various diseases, effect of antacids, effect of food, effect of other drugs (aminophylline, cholestyramine); (2) pharmacokinetics--healthy volunteers, patients with respiratory disease, patients with liver disease, patients with kidney disease, pediatric patients with various diseases, effect of other drugs, enzyme induction of steroids and the effect on the kinetics of steroids and other drugs; (3) protein binding; and (4) analytical methods. The literature is reviewed through August 1979.