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Preliminary in vitro and in vivo investigations on methylprednisolone and its acetate.

Sodium fluoride (6--8 mg/ml) inhibits hydrolysis of methylprednisolone acetate to methylprednisolone. An HPLC method for simultaneous determination of hydrocortisone, methylprednisolone and methylprednisolone acetate in plasma is presented. Analysis of plasma samples (containing NaF) for methylprednisolone acetate shows no significant change in concentration over extended periods of storage at -20 degrees C. In vitro hydrolysis of methylprednisolone acetate at 37 degrees C in human whole blood is rapid (average t1/2 = 19 min). In one cat, the bioavailabilities of methylprednisolone acetate rectally was 13% and of methylprednisolone (alcohol) rectally was 26%, relative to intravenous administration of methylprednisolone. In the same cat, the bioavailabilities of methylprednisolone acetate orally was 93% and of methylprednisolone was 82%, relative to intravenous administration of methylprednisolone. All samples collected after oral administration of methylprednisolone acetate to a human subject were found to contain only methylprednisolone (alcohol) indicating hydrolysis of the drug during absorption through the gastrointestinal membrane and/or in the liver. If the ester had the same half-life in blood in vivo as measured in vitro, it would have been measurable in plasma.

Acetates

The clinical pharmacology of methylprednisolone sodium phosphate. I. Intramuscular route of administration.

Intramuscularly administered methylprednisolone sodium phosphate (Medrol Stabisol) in single doses of 40, 80, or 160 mg (methylprednisolone equivalents) had a similar effect as the same doses of methylprednisolone sodium succinate (Solu-Medrol) with regard to eosinophil suppression, elevation of glucose, white blood count differential shifts (lympholytic effect), urinary excretion of sodium and potassium, and localized (pain) and systemic side effects. The average plasma methylprednisolone concentration was approximately 20% higher after the intramuscular administration of methylprednisolone sodium phosphate than after methylprednisolone sodium succinate. The differences in plasma methylprednisolone levels produced by the two esters suggest that either hydrolysis of the succinate ester occurs more slowly or the succinate ester distributes more extensively. This difference in plasma level, however, is not reflected in any other pharmacologic evaluation of the two esters, e.g., both eosinophil depression and hyperglycemic response were identical. No clinically significant changes in the vital signs, standard hematology, and clinical chemistry parameters evaluated were noted after 21 successive doses (q.i.d. for five days with one dose in the morning of day 6) of 80 mg methylprednisolone sodium phosphate. An increase was noted in the systolic blood pressure from a pretreatment mean of 113 mm Hg to a posttreatment mean of 123 mm Hg and an increase in the body weight from a pretreatment mean of 177 pounds to a posttreatment mean of 183 pounds. No signs of adrenal suppression were found as judged by plasma cortisol and ACTH levels. Six (6/12) subjects of the methylprednisolone sodium phosphate group, one (1/12) subject of the vehicle group, and one (1/12) subject of the placebo (sterile saline) group reported the following systemic side effects: gas in stomach, headaches, anorectal itching, and dryness of itching of the skin. No trend was observed for any side effect reported. In these double-blind, randomized studies, single (40, 80, and 160 mg) and multiple (80 mg) intramuscular doses of methylprednisolone sodium phosphate were tolerated in healthy volunteers as well as the same doses of methylprednisolone sodium succinate and similar volumes of vehicle or placebo.

Adult

Effect of methylprednisolone upon arterial pressure and the renin angiotensin system in the rat.

The effect of methylprednisolone or deoxycorticosterone upon systemic arterial blood pressure and components of the renin-angiotensin system was studied in the rat. Rats maintained on regular diets given methylprednisolone suspension 20 mg/kg body wt demonstrated a significant increase in arterial pressure of + 37 plus or minus 5 mmHg, mean plus or minus SE, over a 2-wk period, whereas those treated with DOC and untreated controls showed no significant change. On normal diets, plasma renin concentration (PRC) of methylprednisolone-treated rats was significantly higher than that of DOC-treated rats. Methylprednisolone treatment also resulted in a significant elevation of plasma renin substrate concentration (PRS). Calculated plasma renin activity (PRA) was highest in methylprednisolone-treated rats, significantly above that of the DOC and no-steroid groups. NaCl supplementation resulted in a significant fall in PRC and PRA in all three groups; however, PRS remained significantly above normal in the methylprednisolone-treated rats. The pressor effect of angiotensin II was slightly increased in methylprednisolone-treated rats. Infusion of [Sar1,Ala8]angiotensin II (P-113) in methylprednisolone-treated rats resulted in a significant fall in diastolic arterial pressure. The results imply that methylprednisolone hypertension in the rat may be in part angiotensin dependent.

Angiotensin II

Rectal and oral absorption of methylprednisolone acetate.

Rectal absorption of methylprednisolone acetate and oral absorption of methylprednisolone and methylprednisolone acetate were investigated in a single-dose 3-way crossover study of 12 normal male volunteers. The median value of bioavailability (relative to oral dose) of methylprednisolone acetate based on unchanged methylprednisolone plasma levels was 14.2% after rectal administration, suggesting that the drug exerts its therapeutic effect topically rather than systemically. In contrast, the median of total radioactivity in urine (as a percentage of rectal dose) was 34.3% (range, 4.52% to 58.8%), suggesting partial bacterial metabolism in the rectum prior to absorption. Mean bioavailability (relative to oral administration of methylprednisolone acetate) of methylprednisolone after oral administration was 89.9%, indicating somewhat better systemic availability of the ester than the alcohol. The average apparent elimination rate constant for methylprednisolone after oral administration of both ester and alcohol was 0.290 hr-1, corresponding to a half-life of 2.39 hr.

Absorption

The effect of methylprednisolone on hepatic oxygen supply and plasma lactate and glucose in endotoxemia.

This study was designed to determine the effect of methylprednisolone on the profile of hepatic oxygen supply and selected blood parameters in fasted, male rats administered an LD85 dosage of E coli endotoxin intraperitoneally. Mortality rates within 24 hours were 85% in rats receiving endotoxin only, 9% in rats receiving a 30 mg/kg dosage of methylprednisolone intraarterially one hour subsequent to endotoxin insult, and 0% in methylprednisolone controls. Beginning with the fourth hour, untreated endotoxin rats had significantly higher heart rates and lower plasma glucose; by the sixth or eighth hour there was significantly greater hypocapnia, lower blood pH, and higher plasma lactate levels in comparison to endotoxic rats receiving methylprednisolone. In addition, mean hepatic pO2 between the sixth and seventh hours was 2.6 mm Hg in endotoxic rats, 10.6 mm Hg in endotoxic methylprednisolone rats, and 17.7 mm Hg in methylprednisolone controls. Methylprednisolone controls showed a steady increase of plasma glucose levels through eight hours but were otherwise stable. Maintenance of hepatic circulation is cited as the probable basis for differences of morbidity and mortality between treated and glucocorticoid-treated endotoxic rats.

Animals

[The effect of methylprednisolone on the course of the experimental tourniquet-shock in dogs (author's transl)].

In experiments in dogs rubber tourniquets were tied around both hind limbs as close to the hip as possible, and a 4-h acute ischemia was induced. With the removal of the tourniquets the tourniquet-shock was produced. In a control group no therapy of the shock was carried out. The animals were observed for 6 h. In a second group, methylprednisolone 40 mg/kg BW was given immediately after revascularisation. In a third group, methylprednisolone 40 mg/kg was given prophylactically 10 min before the tourniquets were applied and therapeutically as soon as the blood circulation was opened. Hemodynamic parameters and renal function were measured to examine the pharmacological effect of methylprednisolone in acute tourniquet-shock. The mortality rate in the control group was 90%, while it was 50% by therapeutic and/or prophylactic application of methylprednisolone. The prophylactic application of methylprednisolone reduced development of metabolic acidosis, hemoconcentration, and hyperkaliemia during ischemia so that a mitigated course of shock was observed.

Animals

Suppression of human cytotoxic lymphocytes by methylprednisolone. An immunosuppressive mechanism of action of steroids.

In order to gain insight into the immunosuppresive mechanism of action of corticosteroids, an in vitro model of the cellular immune response was used to study the effect of methylprednisolone on human lymphocyte-mediated cytotoxicity. Concentrations from 0.25 to 10 microgram/ml were equally effective in producing 74% suppression lymphocyte-mediated cytotoxicity when the steroid was present during the entire period of in vitro sensitization. A 12.5-fold increase in effector to target cell ratio was required to achieve 30% 51Cr release when cytotoxic lymphocytes were generated in the prescence of methylprednisolone. Lymphocyte-mediated cytotoxicity was suppressed 48% when methylprednisolone was present only during the initial 24 hr of the 7-day in vitro sensitization period. Methylprednisolone also effectively inhibited cytotoxicity when it was incubated with sensitized lymphocytes for 3hr before incubating these cells with target cells. Our observations suggest that two of the major immunosuppressive mechanisms of action methylprednisolone are suppression of the generation of cytotoxic lymphocytes and suppression of specifically sensitized cytotoxic lymphocytes.

Cytotoxicity Tests, Immunologic

Protective effect of methylprednisolone on ischaemic myocardium assessed by ventricular function.

Intracardiac surgical procedures are best carried out when the heart is still and bloodless. This condition, however, produces myocardial cellular damage with loss of contractility and compliance unless some protection can be provided. Myocardial contractility and compliance is best studied by isovolumic ventricular function tests, which were used to evaluate the protective effect of methylprednisolone on the isolated cross-perfused canine heart made ischaemic for 2 hours. Control experiments included 2 hours of ischaemia without methylprednisolone, and 2 hours of continuous normothermic cross-perfusion. The methylprednisolone-treated hearts had probably significantly better ventricular function after 2 hours of ischaemia than did hearts without the methylprednisolone, while the cross-perfused hearts were best overall. This work suggests that methylprednisolone may have a protective effect on the ischaemic myocardium of the intact canine heart.

Animals

Inability of methylprednisolone sodium succinate to decrease infarct size or preserve enzyme activity measured 24 hours after coronary occlusion in the dog.

Methylprednisolone sodium succinate (50 mg/kg) was given 30 minutes before or after the start of a 90 minute occlusion of the left circumflex coronary artery (LCX) in one group of dogs. In a second group, methylprednisolone sodium succinate was given 15 minutes after permanent occlusion of the left anterior descending artery (LAD). Infarct size was determined by dehydrogenase staining after 24 or 96 hours. Heart slices were incubated with nitro-blue tetrazolium and nonstaining infarcted tissue was dissected and weighed. Myocardial depletion of creatine phosphokinase activity (CPK) and lactate dehydrogenase activity (LDH) were determined 24 hours after temporary LCX occlusion. When measured after 24 hours, methylprednisolone sodium succinate treatment did not reduce infarct size or decrease enzyme loss. After temporary LCX occlusion infarct size was 30.4 +/- 3.6% of left ventricular weight in control dogs and 30.0 +/- 2.3% in treated dogs. No significant difference in infarct size was observed in hearts examined 24 or 96 hours after myocardial infarction. After permanent LAD occlusion, infarct size in control dogs was 39.2 +/- 1.6% of left ventricular weight and 33.7 +/- 3.5% in treated dogs. CPK activity in the LCX area decreased by 26.5 +/- 7% in controls and by 28.1% +/- 7% in treated dogs. Treated dogs sustained a significantly greater fall in arterial blood pressure after LCX occlusion than did controls. During LCX occlusion and upon reperfusion, methylprednisolone sodium succinate treated dogs exhibited a significantly greater number of premature ventricular beats. Since infarct size and enzyme depletion were not reduced when measured after 24 hours, methylprednisolone sodium succinate treatment does not appear to have enhanced myocardial cell viability.

Animals

The use of methylprednisolone and hypertonic glucose in the prophylaxis of fat embolism syndrome.

In a prospective randomized trial of prophylactic therapy in fat embolism syndrome (FES) 64 patients with femoral and/or tibial shaft fractures uncomplicated by other significant injuries were treated with hypertonic glucose (A), methylprednisolone (B), and placebo (C). Clinical findings and several laboratory parameters were used to establish the diagnosis. Two of the 23 patients in the placebo group (C), 3 of the 21 patients in the hypertonic dextrose (A) group and none of the 20 patients in the methylprednisolone (B) group developed clinical fat embolism syndrome. All patients with fat embolism syndrome were hypoxemic (pO2 less than 65 mm Hg) and exhibited central nervous system symptoms. Four out of 5 were hypocalcemic and 3 patients had thrombocytopenia. There was a high incidence of subclinical hypoxemia or subclinical fat embolism syndrome (29% in A Group, 15% in B Group and 39% in C Group). A comparison between groups of the mean pO2 for each patient demonstrated a statistically significant difference between the methylprednisolone group and the control group (p less than 0.025) as was the comparison of proportions of pO2 less than 70 mm Hg (methylprednisolone versus control p less than 0.01, glucose versus control p less than 0.03). Methylprednisolone given prophylactically may reduce the incidence of fat embolism syndrome and can reduce the degree of hypoxemia associated with long bone fractures of the lower extremmity.

Adult

Reduction of experimental myocardial infarct size by combined treatment with methylprednisolone sodium succinate and betahistine hydrochloride.

This laboratory and others have shown that methylprednisolone sodium succinate and betahistine hydrochloride can each reduce the size of experimental myocardial infarct in dogs at six hours. In light of the fact that these two agents probably act via different mechanisms, a study was carried out to determine if there would be cumulative effects of using these two agents together. Using a left anterior descending coronary artery ligation model to create an experimental myocardial infarction and an intracellular lactic dehydrogenase (LDH) stain to measure the infarct size, 66 dogs were studied. Nineteen dogs served as controls with no therapy; 20 received a continuous intravenous infusion of betahistine hydrochloride (0.24 mg/kg/min) for six hours following ligation; 10 dogs received methylprednisolone sodium succinate intravenously 30 mg/kg at one hour postligation; and 17 other dogs received betahistine hydrochloride intravenously (0.24 mg/kg/min) over six hours following ligation, plus methylprednisolone sodium succinate intravenously (30 mg/kg) at one hour postligation. At six hours, the combined treatment demonstrated no significant improvement over betahistine HCl alone (control, 16.0%; betahistine HCl, 11.4%; combined, 11.2% P less than 0.05). At 24 hours, only the combined treatment group demonstrated a significant infarct size reduction (control, 15.5%; methylprednisolone, 13.1%; betahistine--HCl, 14.2%; combined, 9.7%; P less than 0.0025). Other parameters that were evaluated and analyzed include mean aortic pressure, left atrial pressure, cardiac index, total peripheral resistance, arterial and coronary sinus pH, pCO2, pO2, hematocrit, O2 consumption, O2 content difference, and coronary sinus lactate and creatine phosphokinase (CPK). These results suggest a significant cumulative effect in reducing infarct size over that achieved with one agent alone; however, further studies are needed to determine the appropriate dosage and temporal factors.

Animals

Prevention of peritoneal adhesions in the rat. The effects of dexamethasone, methylprednisolone, promethazine, and human fibrinolysin.

Peritoneal adhesions were created in rats by brisk scrubbing of the terminal part of the ileum. Adhesions were graded by total number and the presence of small bowel obstruction. Adhesion prophylaxis was evaluated using dexamethasone, methylprednisolone sodium succinate, promethazine hydrochloride, and human fibrinolysin (Thrombolysin) in various combinations, doses, and routes of administration. Methylprednisolone and dexamethasone, depending on the route of administration, modified the total number of adhesions but did not modify their severity when compared to control animals. Promethazine by itself modified peritoneal adhesions in the rat. Used together, methylprednisolone and promethazine also modified adhesions, but were not substantially better than the combination of dexamethasone and promethazine. Methylprednisolone, promethazine, and human fibrinolyzin, when used in combination intraperitoneally, virtually eliminated adhesion formation.

Animals

Effect of vitamin A and methylprednisolone on canine prostate in organ culture.

Organ explants from the canine prostate with and without methylprednisolone pretreatment were cultivated for ten days in Trowell's T-8 medium or medium supplemented with testosterone and/or vitamin A. Upon termination of the experiments, explants were fixed and examined histologically. All glands from the most central section of each explant were graded according to epithelial type, and from these grades the proportion of acini with maintained columnar cells was calculated for each explant. Stromal cellular maintenance was also estimated. While a small proportion of explants from the vitamin-treated and methylprednisolone-pretreated groups showed epithelial maintenance, a combination of these treatments significantly increased such maintenance. Stromal maintenance was enhanced with methylprednisolone pretreatment but not by vitamin A. These results are in accord with the hypothesis that methylprednisolone acts to stabilize the lysosomal membrane, thus protecting tissue against the effects of ischemic shock. In protected explants vitamin A is able to maintain a columnar glandular epithelium. In a subsequent experiment a series of linoleic acid dosages was tested in the presence or absence of vitamin A. In neither case was this fatty acid of value in improving epithelial or stromal maintenance.

Animals

Double Latin square study to determine variability and relative bioavailability of methylprednisolone.

The variability and relative bioavailability of methylprednisolone tablets were evaluated utilizing a double Latin square crossover design in which each of 20 subjects was given four of five treatments. Three different lots of methylprednisolone tablets exhibited virtually identical absorption, with similar ranges and coefficients of variation of some selected bioavailability parameters indicative of lot-to-lot uniformity in bioavailability. Within-lot and between-lot uniformities in bioavailability also were similar, suggesting that the observed variability in serum methylprednisolone levels was not due to manufacturing process variables. With respect to intra-versus intersubject variability, no differences were found for the absorption rate or terminal half-life. In contrast, between-subject variability associated with extent of absorption was greater than that within subjects. Relative to an aqueous suspension, methylprednisolone tablets were fully bioavailable.

Adult

High-performance liquid chromatographic determination of hydrocortisone and methylprednisolone and their hemisuccinate esters in human serum.

A high-performance liquid chromatographic method is described for the simultaneous determination of methylprednisolone (MP) and methylprednisolone hemisuccinate (MPHS), or hydrocortisone (HC) and hydrocortisone hemisuccinate (HCHS) in human serum. Reversed-phase liquid chromatography was performed on a microparticulate C18 column (Spherisorb, 5 micron) using a mobile phase of 2% glacial acetic acid, 30--35% acetonitrile, 70--65% water with ultraviolet detection (254 nm). The method uses 17 alpha-hydroxyprogesterone as the internal standard for the determination of methylprednisolone and its hemisuccinate ester, or 11-deoxy-17-hydroxycorticosterone as the internal standard for the determination of hydrocortisone and its hemisuccinate ester. The sensitivity is 0.03 microgram/ml for HC, 0.07 microgram/ml for MP, 0.04 microgram/ml for MPHS, and 0.10 microgram/ml for HCHS, with a detection limit of 0.02 microgram/ml for all four steroids. Calibration curves are linear up to 3 micrograms/ml for MP or MPHS (as equivalent MP) and up to 4 micrograms/ml for HC and 7 micrograms/ml (as equivalent HC) for HCHS. The pooled relative standard deviation for replicate for each steroid is less than 7%. Plasma concentration--time curves are reported for MP and MPHS or HC and HCHS of two human subjects following intramuscular administration of 125 mg of methylprednisolone sodium succinate for injection, U.S.P., or 250 mg of hydrocortisone sodium succinate for injection, U.S.P.

Chromatography, High Pressure Liquid

Effects of methylprednisolone on experimental pulmonary injury.

We studied the effects of methylprednisolone on pulmonary function of unanesthetized dogs with oleic acid induced pulmonary edema observed over a four day period. Methylprednisolone (30 mg/kg) was administered to 11 dogs three and 24 hours after pulmonary injury. Eleven animals were untreated after pulmonary injury and served as controls. There was no difference between the two groups until 72 hours after injury, when the venous admixture of the steroid treated animals was 11 +/- 3% (SD) compared to 22 +/- 8% (p less than 0.001) in the untreated with respective PaO2 values of 76 +/- 6 torr and 64 +/- 8 torr (p less than 0.001). Light microscopic examination of the lungs 96 hours after injury revealed a marked proliferation of Type II pneumocytes in the methylprednisolone treated animals. We conclude that, in the oleic acid or fat embolism model of pulmonary injury, methylprednisolone significantly increases resolution of the pulmonary injury presumably by stimulation of active proliferation and maturation of Type II pneumocytes.

Animals

Feline endotoxin shock: effects of methylprednisolone on kininogen-depletion, on the pulmonary circulation and on survival.

1 Escherichia coli endotoxin, administered intravenously in a dose of 2 mg/kg to pentobarbitone anaesthetized, artificially ventilated cats resulted in pulmonary hypertension, systemic hypotension and an immediate (1-2 min) 30-40% reduction in plasma kininogen, an effect which probably indicates a release of plasma kinins. 2 Methylprednisolone (30 mg/kg), when administered 30 min before endotoxin, did not influence the endotoxin-induced pulmonary hypertension or systemic hypotension but completely prevented the depletion of plasma kininogen. 3 In spontaneously breathing cats, methylprednisolone, administered 30 min after endotoxin, caused a rapid repletion of kininogen and prolonged survival (47% at 6 h compared to 10% in the endotoxinalone animals). Methylprednisolone did not appear to influence lactate production or the hyperventilation observed during the delayed endotoxin shock phase. 4 It is concluded t,at methylprednisolone does not prevent the release, by endotoxin, of a pulmonary vasoconstrictor prostaglandin, or its effects, but that perhaps by preventing kinin release it may reduce endotoxin-induced capillary leakage.

Animals

Effect of hemodialysis on methylprednisolone plasma levels.

The effect of hemodialysis on methylprednisolone levels in uremia was investigated. Methylprednisolone 15 mg/kg was given intravenously over a period of 20 min to five patients undergoing routine maintenance hemodialysis. Dialysis began 5 min after the infusion ended and continued for 5 h. Pre- and post-coil plasma levels and the dialysate level of methylprednisolone were measured at intervals. Dialysance averaged 18.4 +/- 6.1 ml/min, and mean half-life 149 +/- 26 min. The volume of distribution was 0.80 of body weight. The significant dialysance of methylprednisolone may require adjustment of dosage in certain clinical situations when hemodialysis is necessary for patients receiving the steroid.

Half-Life