Oral methylprednisolone has a moderate distribution into tissue at 1.38L/kg.Methylprednisolone is primarily eliminated by hepatic metabolism and renal excretion of metabolites; with renal excretion of unchanged methylprednisolone at only 1.3–9.2%. Methylprednisolone can be interconverted with methylprednisone. Hepatic metabolism is mediated by 11 beta-hydroxysteroid dehydrogenases (11[beta]-HSD) and 20-ketosteroid reductases. Methylprednisolone undergoes renal excretion of hydrophilic inactive metabolites, including 20-carboxymelthylprednisolone and 6[beta]-hydroxy-20[alpha]-hydroxymethylprednisolone. Medical uses
As stated previously, the primary use of methylprednisolone is to suppress inflammatory and immune responses. Methylprednisolone achieves this primarily by regulating the number and function of leukocytes, cytokines and chemokines. Its widespread inflammatory control is conducive in use across multiple disorders regardless of pathology. Methylprednisolone is commonly prescribed as short-term therapy for acute flares, as seen with acute gouty arthritis. It can be prescribed during on-going therapy in lower doses contingent upon monitorization of adverse effects. Dosage strength and formulation are optimized per medical use. Asthma
In 2001–2002, 11.4% of patients diagnosed with asthma and seen at an outpatient visit were prescribed oral corticosteroids as a long-term control therapy. The National Asthma Education and Prevention Program (NAEPP) indicates systemic methylprednisolone in both short and long term therapies to quickly control and to suppress persistent asthma, respectively. For exacerbations that result in a visit to the Emergency Department (ED), oral methylprednisolone is preferred over intravenous administration, unless there are issues with adherence or vomiting. Oral methylprednisolone is less invasive and studies have shown that equivalent efficacy compared to intravenous methylprednisolone.
This association changes physiochemical properties of the membrane; activating membrane proteins, altering cellular functions and ultimately influencing cation transport through the plasma membrane and stimulating the proton leak across the inner mitochondrial membrane. Hindered oxidative phosphorylation compromises ATP production, a major energy source for cellular energy metabolism and immune function. In vivo studies of Con-A stimulated thymocytes (in rats) and human immune cells that were administered high doses of methylprednisolone has been shown to inhibit respiration in a dose-dependent manner, inhibit plasma calcium and sodium uptake, and increase cytoplasmic calcium concentration. The summative process is as follows: Methylprednisolone intercalates in the plasma membrane, causes physiochemical changes, activates membrane proteins that inhibit plasma calcium and sodium uptake (mimicking an energy deficit state). ATP consumption drops (resembled by inhibited respiration), resulting in protein permeability at the inner mitochondrial membrane and uncoupling of oxidative phosphorylation. Of notable importance, DNA/RNA synthesis was not hindered. The dependency of house keeping cells and immune cells on ATP, results in immunosuppression during ATP deficit. Specific immune functions effected by this process are cytokinesis, migration, phagocytosis, antigen processing and presenting, antibody synthesis, cytotoxicity and regulation. The HPA axis
The activation of the hypothalamic-pituitary axis (HPA axis) stimulates the production of endogenous glucocorticoids within the adrenal cortex. The HPA axis interprets stimuli (stress, inflammation and circadian cues) and transduces a corresponding physiochemical response. Glucocorticoids released in the blood, serve as a messenger by binding to glucocorticoid receptors in a wide distribution across the body, including the HPA axis itself.