Adrenocorticosteroid Pharmacology

Correct Answer

C — Budesonide

Rationale

Budesonide is classified as a high first-pass hepatic metabolism inhaled corticosteroid: approximately 85 to 90% of the systemically absorbed fraction is inactivated on first pass through the liver, limiting systemic glucocorticoid receptor activation and adverse effects. Fluticasone propionate achieves low systemic bioavailability primarily through poor gastrointestinal absorption rather than first-pass metabolism. Ciclesonide is an inactive prodrug activated by airway esterases. Triamcinolone acetonide has higher systemic bioavailability than budesonide.

Correct Answer

A — Ciclesonide

Rationale

Ciclesonide is classified as an inhaled corticosteroid prodrug: it is pharmacologically inactive as inhaled and is converted to its active metabolite, des-ciclesonide, by esterases in the airway epithelium. This targeted activation at the site of action limits systemic bioavailability. Budesonide, fluticasone propionate, and beclomethasone dipropionate are active as administered and do not require enzymatic conversion at the airway to exert their anti-inflammatory effects.

Correct Answer

D — Methylprednisolone

Rationale

Methylprednisolone is classified as the glucocorticoid used for intravenous pulse therapy in severe organ-threatening autoimmune disease. In lupus nephritis, neuropsychiatric lupus, and lupus myocarditis, intravenous methylprednisolone 500 to 1000 mg per day for 3 days delivers rapid high-potency immunosuppression to halt acute organ damage, followed by oral prednisone. Hydrocortisone is used for replacement therapy and septic shock dosing. Prednisone is an oral agent used for maintenance. Fludrocortisone is a mineralocorticoid replacement agent.

Correct Answer

B — Dexamethasone

Rationale

Dexamethasone is the preferred glucocorticoid for cerebral edema and bacterial meningitis because of its high potency, no mineralocorticoid activity, and long biologic duration — properties that make it the standard agent in both settings. In bacterial meningitis, it is given with or immediately before the first antibiotic dose to suppress the intense subarachnoid inflammatory response triggered by bacterial lysis. Hydrocortisone has significant mineralocorticoid activity and short duration. Prednisone requires hepatic conversion and is an oral agent. Methylprednisolone is used for intravenous pulse therapy in autoimmune disease.

Correct Answer

A — Tocilizumab

Rationale

Tocilizumab is classified as an interleukin-6 receptor antagonist and is approved as adjunctive therapy in giant cell arteritis, where it enables a faster prednisone taper with fewer relapses than prednisone monotherapy. Rituximab is an anti-CD20 monoclonal antibody targeting B cells. Methotrexate is a disease-modifying antirheumatic drug used in rheumatoid arthritis and other inflammatory conditions. Belimumab is a B-lymphocyte stimulator inhibitor approved in systemic lupus erythematosus.

Correct Answer

C — Hydrocortisone

Rationale

Hydrocortisone is the appropriate agent for septic shock stress dosing: 200 mg per day by continuous infusion or 50 mg intravenously every 6 hours for patients refractory to adequate fluid resuscitation and vasopressors. Its mineralocorticoid activity contributes to hemodynamic stabilization, and its short plasma half-life allows rapid dose adjustment. Dexamethasone is avoided in septic shock because of its long biologic duration and complete absence of mineralocorticoid activity. Prednisone is an oral agent and a prodrug. Fludrocortisone is a mineralocorticoid agonist used as an adjunct in some septic shock protocols, not as the primary agent.

Correct Answer

B — Tethering to the p65 subunit blocking coactivator binding, induction of I-kappa-B-alpha to sequester nuclear factor kappa-B in the cytoplasm, and recruitment of histone deacetylase 2 to close chromatin at target gene promoters

Rationale

Glucocorticoids suppress nuclear factor kappa-B through three parallel mechanisms: (1) the glucocorticoid receptor monomer tethers directly to the p65 subunit of nuclear factor kappa-B, blocking coactivator binding and preventing transcriptional activation; (2) glucocorticoids induce I-kappa-B-alpha, the inhibitory protein that sequesters nuclear factor kappa-B in the cytoplasm, preventing its nuclear entry; and (3) the glucocorticoid receptor recruits histone deacetylase 2 to promoters of nuclear factor kappa-B target genes, reversing histone acetylation and closing chromatin. The histone deacetylase 2 mechanism is particularly relevant to glucocorticoid resistance in chronic obstructive pulmonary disease.

Correct Answer

D — Glucocorticoids alter homing receptor expression on T cells, causing redistribution to lymphoid tissues, and suppress interleukin-2 production, preventing antigen-activated T cell clonal expansion

Rationale

Glucocorticoid-induced lymphopenia has two components. Acutely, altered homing receptor expression drives T cell redistribution from the blood to lymphoid tissues (spleen, lymph nodes, bone marrow), reducing circulating counts by 70 to 90% within hours — an effect that reverses within 24 hours of a single dose. The sustained immunosuppressive effect depends primarily on suppression of interleukin-2 production by T helper cells: without interleukin-2, antigen-activated T cells cannot undergo clonal expansion to mount an adaptive immune response. At high concentrations or with prolonged exposure, glucocorticoids also induce apoptosis in immature thymocytes, contributing to lymphoid atrophy over time.

Correct Answer

A — Approximately 85 to 90% of the systemically absorbed fraction of budesonide undergoes first-pass hepatic metabolism to inactive compounds, limiting systemic glucocorticoid receptor activation

Rationale

Budesonide achieves a favorable systemic safety profile primarily through high first-pass hepatic metabolism: approximately 85 to 90% of the absorbed fraction is inactivated on the first pass through the liver, preventing it from reaching systemic glucocorticoid receptors in bone, muscle, skin, and metabolic tissues. This is the pharmacokinetic basis for the transactivation/transrepression separation described in Module 1 — local anti-inflammatory transrepression in the airway occurs before hepatic inactivation limits systemic transactivation. Budesonide binds the glucocorticoid receptor with high affinity and is well absorbed across airway epithelium; low receptor affinity and poor airway absorption are not the mechanisms.

Correct Answer

C — Dexamethasone has a long biologic duration that prevents rapid dose adjustment and lacks the mineralocorticoid activity needed to support hemodynamic stabilization

Rationale

Dexamethasone is not preferred for septic shock stress dosing for two pharmacological reasons: its long biologic half-life of 36 to 54 hours prevents rapid dose titration as the patient's hemodynamic status changes, and it has no mineralocorticoid activity — an important limitation in septic shock where sodium retention and vascular tone support are part of the mechanism of benefit. Hydrocortisone provides both glucocorticoid stress coverage and mineralocorticoid support, and its short half-life allows dose adjustment. Dexamethasone is available intravenously and has high anti-inflammatory potency — properties that make it appropriate in other acute illness contexts but do not overcome these two pharmacological limitations in septic shock.

Correct Answer

B — Glucocorticoids promote eosinophil apoptosis, and the resulting eosinopenia is one of the most sensitive indicators of glucocorticoid receptor engagement

Rationale

Glucocorticoids rapidly and markedly reduce blood eosinophil numbers by promoting eosinophil apoptosis — a mechanism distinct from the redistribution that underlies glucocorticoid-induced neutrophilia and lymphopenia. The fall in blood eosinophil count after a single systemic glucocorticoid dose is one of the most sensitive indicators of glucocorticoid receptor engagement. A rising eosinophil count in a patient who should be therapeutically suppressed raises the question of non-compliance or inadequate dosing. Mast cell numbers in tissues are also reduced with prolonged use through suppression of stem cell factor. These effects explain much of glucocorticoid efficacy in asthma and allergic disease.

Correct Answer

D — Dexamethasone suppresses the intense subarachnoid inflammatory response triggered when antibiotics lyse bacteria and release cell wall components

Rationale

When antibiotics kill bacteria in the subarachnoid space, rapid lysis releases bacterial cell wall components that trigger an intense inflammatory cascade. This inflammation — not the infection itself — drives sensorineural hearing loss (from cochlear injury), cerebral edema, and vasculitis. Dexamethasone given with or immediately before the first antibiotic dose suppresses this lysis-triggered inflammatory response through nuclear factor kappa-B inhibition and cytokine suppression, reducing the peak of subarachnoid inflammation. Timing is critical: given after the first antibiotic dose, much of the inflammatory trigger from initial lysis has already occurred.

Correct Answer

A — Glucocorticoids suppress interleukin-2 gene transcription by inhibiting nuclear factor kappa-B, while calcineurin inhibitors block the nuclear factor of activated T cells pathway; together they suppress interleukin-2 production more completely than either agent alone

Rationale

Interleukin-2 gene transcription requires activation of multiple transcription factors, including both nuclear factor kappa-B and the nuclear factor of activated T cells. Glucocorticoids suppress nuclear factor kappa-B through tethering, I-kappa-B-alpha induction, and histone deacetylase 2 recruitment — blocking the nuclear factor kappa-B-dependent arm of interleukin-2 transcription. Calcineurin inhibitors (cyclosporine, tacrolimus) block calcineurin, the phosphatase required to dephosphorylate and activate the nuclear factor of activated T cells transcription factor — blocking that arm of interleukin-2 transcription. Because the two drug classes target distinct upstream pathways converging on the same gene, their combination produces additive to synergistic interleukin-2 suppression at doses that are individually insufficient.

Correct Answer

C — Oxidative stress from cigarette smoke inactivates histone deacetylase 2 in airway macrophages, impairing the glucocorticoid receptor's ability to close chromatin at nuclear factor kappa-B target gene promoters

Rationale

One of the three parallel mechanisms by which glucocorticoids suppress nuclear factor kappa-B is recruitment of histone deacetylase 2 to inflammatory gene promoters, which reverses histone acetylation and closes chromatin. In chronic obstructive pulmonary disease patients who smoke, oxidative stress generated by cigarette smoke inactivates histone deacetylase 2 in airway macrophages. Without functional histone deacetylase 2, the glucocorticoid receptor can still tether to p65 and induce I-kappa-B-alpha, but the chromatin-closing arm of nuclear factor kappa-B suppression is absent — producing partial glucocorticoid resistance. This is why high-dose inhaled corticosteroids often provide limited benefit in active smokers with chronic obstructive pulmonary disease.

Correct Answer

B — High-dose prednisone or intravenous methylprednisolone to suppress cranial artery inflammation and prevent ischemic optic neuropathy

Rationale

This presentation is giant cell arteritis with visual prodrome: transient monocular visual dimming in this clinical context represents threatened anterior ischemic optic neuropathy from inflammatory occlusion of the ophthalmic artery or its branches. High-dose glucocorticoids — prednisone 40 to 60 mg per day or intravenous methylprednisolone pulse when visual symptoms are present — must be started immediately. Treatment is not delayed for biopsy: even 24 hours of delay can cause permanent blindness. The mechanism of benefit is suppression of granulomatous arterial wall inflammation through nuclear factor kappa-B inhibition and cytokine suppression. Tocilizumab is approved as adjunctive therapy to enable faster prednisone tapering, not as initial monotherapy.

Correct Answer

A — Oxidative stress from cigarette smoke has inactivated histone deacetylase 2 in his airway macrophages, preventing the glucocorticoid receptor from closing chromatin at inflammatory gene promoters

Rationale

Glucocorticoid resistance in chronic obstructive pulmonary disease is mechanistically linked to cigarette smoke-induced oxidative inactivation of histone deacetylase 2 in airway macrophages. This enzyme is required for one of the three parallel mechanisms by which glucocorticoids suppress nuclear factor kappa-B: recruitment of histone deacetylase 2 to inflammatory gene promoters reverses histone acetylation and closes chromatin, reducing transcription of pro-inflammatory cytokines. Without functional histone deacetylase 2, this arm of suppression is lost, producing partial resistance to anti-inflammatory effects even at high doses. This explains why response to inhaled corticosteroids in chronic obstructive pulmonary disease is substantially less than in eosinophilic asthma, even with confirmed compliance.

Correct Answer

D — Dexamethasone provides high anti-inflammatory potency at a small once-daily dose with no mineralocorticoid activity, which is appropriate for dysregulated inflammatory lung injury rather than hemodynamic support

Rationale

The RECOVERY trial established dexamethasone 6 mg once daily as the evidence-based regimen for COVID-19 acute respiratory distress syndrome requiring respiratory support. Dexamethasone was selected for three pharmacological properties: high anti-inflammatory potency delivered at a small, easily administered dose; once-daily dosing convenient for patients requiring inpatient care; and absence of mineralocorticoid activity — appropriate when the therapeutic goal is suppressing dysregulated host inflammation in the lung rather than the hemodynamic support for which mineralocorticoid activity is useful in septic shock. Dexamethasone has a long biologic half-life, not a short one, and no selective transrepression advantage has been demonstrated in patients.

Correct Answer

C — Rifampin induces CYP3A4, accelerating hepatic metabolism of both prednisone and tacrolimus and reducing their plasma concentrations

Rationale

Rifampin is a potent inducer of CYP3A4, the primary enzyme responsible for hepatic metabolism of both glucocorticoids and calcineurin inhibitors. CYP3A4 induction accelerates conversion of prednisolone (the active metabolite of prednisone) to inactive compounds and increases tacrolimus clearance, reducing the plasma concentrations of both immunosuppressants. The result is a pharmacokinetic drug interaction that can precipitate acute allograft rejection even when the patient is compliant with the transplant regimen. In transplant patients requiring tuberculosis therapy, rifampin is often replaced with rifabutin — a less potent CYP3A4 inducer — or immunosuppressant doses are substantially increased with close monitoring.