Glucocorticoids

Chemistry and Pharmacodynamics

Chemical structure

• Glucocorticoids are synthetic analogs of cortisol and cortisone.
• Alterations may include:
  • Fluorination ( dexamethasone Dexamethasone An anti-inflammatory 9-fluoro-glucocorticoid. Antiemetics, betamethasone)
  • Methylation ( methylprednisolone Methylprednisolone A prednisolone derivative with similar anti-inflammatory action. Immunosuppressants)

Physiology

• Endogenous glucocorticoids are:
  • Derived from cholesterol Cholesterol The principal sterol of all higher animals, distributed in body tissues, especially the brain and spinal cord, and in animal fats and oils. Cholesterol Metabolism (which is synthesized from acetyl-CoA Acetyl-CoA Acetyl CoA participates in the biosynthesis of fatty acids and sterols, in the oxidation of fatty acids and in the metabolism of many amino acids. It also acts as a biological acetylating agent. Citric Acid Cycle)
  • Secreted from the zona fasciculata Zona Fasciculata The wide middle zone of the adrenal cortex. This zone produces a series of enzymes that convert pregnenolone to cortisol (hydrocortisone) via 17-alpha-hydroxyprogesterone. Adrenal Glands: Anatomy
• Effects: respond to immediate stressors
  • ↑ Immediate available energy through: 
    • Fat and protein catabolism → ↑ blood amino acid Amino acid Amino acids (AAs) are composed of a central carbon atom attached to a carboxyl group, an amino group, a hydrogen atom, and a side chain (R group). Basics of Amino Acids and lipid levels
    • Gluconeogenesis Gluconeogenesis Gluconeogenesis is the process of making glucose from noncarbohydrate precursors. This metabolic pathway is more than just a reversal of glycolysis. Gluconeogenesis provides the body with glucose not obtained from food, such as during a fasting period. The production of glucose is critical for organs and cells that cannot use fat for fuel. Gluconeogenesis
    • Appetite stimulation
  • ↑ RBCs RBCs Erythrocytes, or red blood cells (RBCs), are the most abundant cells in the blood. While erythrocytes in the fetus are initially produced in the yolk sac then the liver, the bone marrow eventually becomes the main site of production. Erythrocytes: Histology
  • ↑ Serum calcium Calcium A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes. Electrolytes from bone resorption Bone resorption Bone loss due to osteoclastic activity. Bones: Remodeling and Healing (leads to ↓ bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types mineral density over time)
  • Antiinflammatory effects:
    • ↓ Inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation
    • ↓ Blood vessel permeability
    • Long-term exposure suppresses the immune system Immune system The body’s defense mechanism against foreign organisms or substances and deviant native cells. It includes the humoral immune response and the cell-mediated response and consists of a complex of interrelated cellular, molecular, and genetic components. Primary Lymphatic Organs
• Regulated by the hypothalamic-pituitary-adrenal (HPA) axis

Mechanism of action

• Glucocorticoids enter cell → bind BIND Hyperbilirubinemia of the Newborn to glucocorticoid receptors Receptors Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors 
• Translocation to the nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles → bind BIND Hyperbilirubinemia of the Newborn to specific DNA DNA A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine). DNA Types and Structure sequences (glucocorticoid response elements) → result in either:
  • Activation of transcription Transcription Transcription of genetic information is the first step in gene expression. Transcription is the process by which DNA is used as a template to make mRNA. This process is divided into 3 stages: initiation, elongation, and termination. Stages of Transcription
  • Repression Repression Defense mechanisms involving approach and avoidance responses to threatening stimuli. The sensitizing process involves intellectualization in approaching or controlling the stimulus whereas repression involves unconscious denial in avoiding the stimulus. Defense Mechanisms of transcription Transcription Transcription of genetic information is the first step in gene expression. Transcription is the process by which DNA is used as a template to make mRNA. This process is divided into 3 stages: initiation, elongation, and termination. Stages of Transcription
• Results in metabolic effects (similar to normal physiology)
• Specific genomic immune system Immune system The body’s defense mechanism against foreign organisms or substances and deviant native cells. It includes the humoral immune response and the cell-mediated response and consists of a complex of interrelated cellular, molecular, and genetic components. Primary Lymphatic Organs effects include:
  • Blocking promotor sites for proinflammatory genes Genes A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. DNA Types and Structure
  • Promoting transcription Transcription Transcription of genetic information is the first step in gene expression. Transcription is the process by which DNA is used as a template to make mRNA. This process is divided into 3 stages: initiation, elongation, and termination. Stages of Transcription of antiinflammatory gene Gene A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. Basic Terms of Genetics products
  • Diminish synthesis Synthesis Polymerase Chain Reaction (PCR) of inflammatory cytokines Cytokines Non-antibody proteins secreted by inflammatory leukocytes and some non-leukocytic cells, that act as intercellular mediators. They differ from classical hormones in that they are produced by a number of tissue or cell types rather than by specialized glands. They generally act locally in a paracrine or autocrine rather than endocrine manner. Adaptive Immune Response
• Additional effects:
  • ↓ Inflammatory cytokine secretion Secretion Coagulation Studies
  • ↑ ACE synthesis Synthesis Polymerase Chain Reaction (PCR) → bradykinin Bradykinin A nonapeptide messenger that is enzymatically produced from kallidin in the blood where it is a potent but short-lived agent of arteriolar dilation and increased capillary permeability. Bradykinin is also released from mast cells during asthma attacks, from gut walls as a gastrointestinal vasodilator, from damaged tissues as a pain signal, and may be a neurotransmitter. Hereditary Angioedema (C1 Esterase Inhibitor Deficiency) degradation
    • ↓ Capillary permeability
    • ↓ Vasodilation Vasodilation The physiological widening of blood vessels by relaxing the underlying vascular smooth muscle. Pulmonary Hypertension Drugs
  • ↓ Synthesis Synthesis Polymerase Chain Reaction (PCR) of phospholipase A2 Phospholipase A2 Phospholipases that hydrolyze the Acyl group attached to the 2-position of phosphoglycerides. Nephrotic Syndrome and COX-2 → ↓ prostaglandin and leukotriene Leukotriene Asthma Drugs synthesis Synthesis Polymerase Chain Reaction (PCR)
  • ↓ Migration of PMNs 
  • ↓ Histamine release Release Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane. Virology

Classification

By use

• Systemic (see below) 
• Topical:
  • Betamethasone
  • Clobetasol
  • Fluocinomide
  • Fluticasone
  • Hydrocortisone Hydrocortisone The main glucocorticoid secreted by the adrenal cortex. Its synthetic counterpart is used, either as an injection or topically, in the treatment of inflammation, allergy, collagen diseases, asthma, adrenocortical deficiency, shock, and some neoplastic conditions. Immunosuppressants
  • Mometasone Mometasone Asthma Drugs
  • Triamcinolone
• Inhaled:
  • Beclomethasone Beclomethasone An anti-inflammatory, synthetic glucocorticoid. It is used topically as an anti-inflammatory agent and in aerosol form for the treatment of asthma. Asthma Drugs 
  • Budesonide Budesonide A glucocorticoid used in the management of asthma, the treatment of various skin disorders, and allergic rhinitis. Asthma Drugs
  • Fluticasone 
  • Mometasone Mometasone Asthma Drugs

By duration of action

Systemic glucocorticoids can be divided into:

• Short-acting:
  • Cortisone
  • Hydrocortisone Hydrocortisone The main glucocorticoid secreted by the adrenal cortex. Its synthetic counterpart is used, either as an injection or topically, in the treatment of inflammation, allergy, collagen diseases, asthma, adrenocortical deficiency, shock, and some neoplastic conditions. Immunosuppressants
• Intermediate-acting:
  • Methylprednisolone Methylprednisolone A prednisolone derivative with similar anti-inflammatory action. Immunosuppressants
  • Prednisolone Prednisolone A glucocorticoid with the general properties of the corticosteroids. It is the drug of choice for all conditions in which routine systemic corticosteroid therapy is indicated, except adrenal deficiency states. Immunosuppressants
  • Prednisone Prednisone A synthetic anti-inflammatory glucocorticoid derived from cortisone. It is biologically inert and converted to prednisolone in the liver. Immunosuppressants
  • Triamcinolone
• Long-acting:
  • Betamethasone
  • Dexamethasone Dexamethasone An anti-inflammatory 9-fluoro-glucocorticoid. Antiemetics

By potency

Topical steroids Steroids A group of polycyclic compounds closely related biochemically to terpenes. They include cholesterol, numerous hormones, precursors of certain vitamins, bile acids, alcohols (sterols), and certain natural drugs and poisons. Steroids have a common nucleus, a fused, reduced 17-carbon atom ring system, cyclopentanoperhydrophenanthrene. Most steroids also have two methyl groups and an aliphatic side-chain attached to the nucleus. Benign Liver Tumors are classified as classes I–VII based on their potency.

• Class I: most potent; includes:
  • Clobetasol propionate Clobetasol propionate A derivative of prednisolone with high glucocorticoid activity and low mineralocorticoid activity. Absorbed through the skin faster than fluocinonide, it is used topically in treatment of psoriasis but may cause marked adrenocortical suppression. Bullous Pemphigoid and Pemphigus Vulgaris
  • Betamethasone dipropionate
  • Diflorasone diacetate
  • Fluocinonide 
• Class VII: least potent; includes hydrocortisone Hydrocortisone The main glucocorticoid secreted by the adrenal cortex. Its synthetic counterpart is used, either as an injection or topically, in the treatment of inflammation, allergy, collagen diseases, asthma, adrenocortical deficiency, shock, and some neoplastic conditions. Immunosuppressants

Pharmacokinetics

The following summarizes the pharmacokinetics Pharmacokinetics Pharmacokinetics is the science that analyzes how the human body interacts with a drug. Pharmacokinetics examines how the drug is absorbed, distributed, metabolized, and excreted by the body. Pharmacokinetics and Pharmacodynamics for systemic glucocorticoids:

Absorption Absorption Absorption involves the uptake of nutrient molecules and their transfer from the lumen of the GI tract across the enterocytes and into the interstitial space, where they can be taken up in the venous or lymphatic circulation. Digestion and Absorption

• Oral absorption Absorption Absorption involves the uptake of nutrient molecules and their transfer from the lumen of the GI tract across the enterocytes and into the interstitial space, where they can be taken up in the venous or lymphatic circulation. Digestion and Absorption is:
  • Rapid
  • Complete
• Formulations/routes of administration:
  • Oral
  • IV
  • IM
  • Intraarticular

Distribution

• Protein binding:
  • Natural glucocorticoids are highly protein-bound:
    • Corticosteroid-binding globulin (CBG)
    • Albumin Albumin Serum albumin from humans. It is an essential carrier of both endogenous substances, such as fatty acids and bilirubin, and of xenobiotics in the blood. Liver Function Tests
  • Synthetic steroids Steroids A group of polycyclic compounds closely related biochemically to terpenes. They include cholesterol, numerous hormones, precursors of certain vitamins, bile acids, alcohols (sterols), and certain natural drugs and poisons. Steroids have a common nucleus, a fused, reduced 17-carbon atom ring system, cyclopentanoperhydrophenanthrene. Most steroids also have two methyl groups and an aliphatic side-chain attached to the nucleus. Benign Liver Tumors are generally less protein-bound.
• Cross the blood– brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification barrier

Metabolism and excretion

• Metabolism:
  • Hepatic
  • Some by CYP3A4 CYP3A4 Class 3 Antiarrhythmic Drugs (Potassium Channel Blockers)
• Excretion: primarily in urine

Indications

Systemic

Systemic glucocorticoids are commonly used for the short- and/or long-term management of a variety of conditions, including:

• Physiologic glucocorticoid replacement
• Inflammatory diseases
• Allergic conditions
• Autoimmune diseases Autoimmune diseases Disorders that are characterized by the production of antibodies that react with host tissues or immune effector cells that are autoreactive to endogenous peptides. Selective IgA Deficiency

Topical

Topical glucocorticoids can be used for a number of dermatologic conditions, including (list is not exhaustive):

• Psoriasis Psoriasis Psoriasis is a common T-cell-mediated inflammatory skin condition. The etiology is unknown, but is thought to be due to genetic inheritance and environmental triggers. There are 4 major subtypes, with the most common form being chronic plaque psoriasis. Psoriasis 
• Atopic dermatitis Dermatitis Any inflammation of the skin. Atopic Dermatitis (Eczema) 
• Acute radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma dermatitis Dermatitis Any inflammation of the skin. Atopic Dermatitis (Eczema)
• Lichen planus Lichen planus Lichen planus (LP) is an idiopathic, cell-mediated inflammatory skin disease. It is characterized by pruritic, flat-topped, papular, purple skin lesions commonly found on the flexural surfaces of the extremities. Other areas affected include genitalia, nails, scalp, and mucous membranes. Lichen Planus
• Discoid lupus erythematosus Discoid Lupus Erythematosus Alopecia 
• Vitiligo Vitiligo Vitiligo is the most common depigmenting disorder and is caused by the destruction of melanocytes. Patients present with hypo- or depigmented macules or patches which often occur on the face, hands, knees, and/or genitalia. Vitiligo

Inhaled

• Persistent asthma Asthma Asthma is a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. The disease is believed to result from the complex interaction of host and environmental factors that increase disease predisposition, with inflammation causing symptoms and structural changes. Patients typically present with wheezing, cough, and dyspnea. Asthma (prevent exacerbations)
• Stable chronic obstructive pulmonary disease Chronic obstructive pulmonary disease Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in middle-aged or elderly persons with a history of cigarette smoking. Signs and symptoms include prolonged expiration, wheezing, diminished breath sounds, progressive dyspnea, and chronic cough. Chronic Obstructive Pulmonary Disease (COPD) (prevent exacerbations)
• Eosinophilic esophagitis Esophagitis Esophagitis is the inflammation or irritation of the esophagus. The major types of esophagitis are medication-induced, infectious, eosinophilic, corrosive, and acid reflux. Patients typically present with odynophagia, dysphagia, and retrosternal chest pain. Esophagitis (not inhaled, but swallowed)

Adverse Effects and Contraindications

Adverse effects

• Endocrine:
  • Cushingoid features
  • Cushing syndrome Cushing syndrome A condition caused by prolonged exposure to excess levels of cortisol (hydrocortisone) or other glucocorticoids from endogenous or exogenous sources. It is characterized by upper body obesity; osteoporosis; hypertension; diabetes mellitus; hirsutism; amenorrhea; and excess body fluid. Endogenous Cushing syndrome or spontaneous hypercortisolism is divided into two groups, those due to an excess of adrenocorticotropin and those that are acth-independent. Paraneoplastic Syndromes
  • Hyperglycemia Hyperglycemia Abnormally high blood glucose level. Diabetes Mellitus and diabetes mellitus Diabetes mellitus Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus
  • Growth suppression Suppression Defense Mechanisms in children and adolescents
  • Weight gain
• Immunologic/infectious:
  • Thrush
  • Immunosuppression → invasive infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease
• Hematologic: neutrophilia from demargination
• GI:
  • Ulcers
  • Gastritis Gastritis Gastritis refers to inflammation of the gastric mucosa. Gastritis may occur suddenly (acute gastritis) or slowly over time (chronic gastritis). Gastritis may be asymptomatic or with symptoms, including burning abdominal pain (which either worsens or improves with eating), dyspepsia, nausea, and vomiting. Gastritis
• Neurologic:
  • Psychosis
  • Insomnia Insomnia Insomnia is a sleep disorder characterized by difficulty in the initiation, maintenance, and consolidation of sleep, leading to impairment of function. Patients may exhibit symptoms such as difficulty falling asleep, disrupted sleep, trouble going back to sleep, early awakenings, and feeling tired upon waking. Insomnia
  • Irritability
  • Anxiety Anxiety Feelings or emotions of dread, apprehension, and impending disaster but not disabling as with anxiety disorders. Generalized Anxiety Disorder
  • Mood lability
  • ↑ Appetite
• Ophthalmologic: 
  • Glaucoma Glaucoma Glaucoma is an optic neuropathy characterized by typical visual field defects and optic nerve atrophy seen as optic disc cupping on examination. The acute form of glaucoma is a medical emergency. Glaucoma is often, but not always, caused by increased intraocular pressure (IOP). Glaucoma
  • Cataracts
• Musculoskeletal:
  • Myopathy Myopathy Dermatomyositis: 
    • Proximal muscle weakness Proximal Muscle Weakness Lambert-Eaton Myasthenic Syndrome
    • Myalgias Myalgias Painful sensation in the muscles. Tick-borne Encephalitis Virus
  • Osteoporosis Osteoporosis Osteoporosis refers to a decrease in bone mass and density leading to an increased number of fractures. There are 2 forms of osteoporosis: primary, which is commonly postmenopausal or senile; and secondary, which is a manifestation of immobilization, underlying medical disorders, or long-term use of certain medications. Osteoporosis
  • Osteonecrosis
• Dermatologic:
  • Skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions atrophy Atrophy Decrease in the size of a cell, tissue, organ, or multiple organs, associated with a variety of pathological conditions such as abnormal cellular changes, ischemia, malnutrition, or hormonal changes. Cellular Adaptation
  • Striae
  • Purpura
  • Impaired wound healing Wound healing Wound healing is a physiological process involving tissue repair in response to injury. It involves a complex interaction of various cell types, cytokines, and inflammatory mediators. Wound healing stages include hemostasis, inflammation, granulation, and remodeling. Wound Healing
  • Hypertrichosis
• Withdrawal:
  • Long-term therapy results in HPA-axis suppression Suppression Defense Mechanisms
  • Abrupt discontinuation may cause adrenal insufficiency Adrenal Insufficiency Conditions in which the production of adrenal corticosteroids falls below the requirement of the body. Adrenal insufficiency can be caused by defects in the adrenal glands, the pituitary gland, or the hypothalamus. Adrenal Insufficiency and Addison’s Disease

Contraindications Contraindications A condition or factor associated with a recipient that makes the use of a drug, procedure, or physical agent improper or inadvisable. Contraindications may be absolute (life threatening) or relative (higher risk of complications in which benefits may outweigh risks). Noninvasive Ventilation and precautions

• Contraindications Contraindications A condition or factor associated with a recipient that makes the use of a drug, procedure, or physical agent improper or inadvisable. Contraindications may be absolute (life threatening) or relative (higher risk of complications in which benefits may outweigh risks). Noninvasive Ventilation:
  • Recent administration of live or live attenuated vaccines
  • Systemic fungal infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease
  • Other uncontrolled active infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease
• Use with caution with:
  • Psychosis
  • Uncontrolled hyperglycemia Hyperglycemia Abnormally high blood glucose level. Diabetes Mellitus
  • Osteoporosis Osteoporosis Osteoporosis refers to a decrease in bone mass and density leading to an increased number of fractures. There are 2 forms of osteoporosis: primary, which is commonly postmenopausal or senile; and secondary, which is a manifestation of immobilization, underlying medical disorders, or long-term use of certain medications. Osteoporosis
  • Diverticulitis Diverticulitis Inflammation of a diverticulum or diverticula. Diverticular Disease or recent intestinal anastomoses → risk of perforation Perforation A pathological hole in an organ, blood vessel or other soft part of the body, occurring in the absence of external force. Esophagitis
  • Severe hepatic or renal impairment
  • Recent acute MI MI MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction → risk of wall rupture

Drug interactions

• ↑ Risk of ulcers and GI bleeding: NSAIDs NSAIDS Primary vs Secondary Headaches
• ↓ Absorption Absorption Absorption involves the uptake of nutrient molecules and their transfer from the lumen of the GI tract across the enterocytes and into the interstitial space, where they can be taken up in the venous or lymphatic circulation. Digestion and Absorption of glucocorticoids:
  • Proton pump inhibitors Proton Pump Inhibitors Compounds that inhibit h(+)-k(+)-exchanging ATPase. They are used as anti-ulcer agents and sometimes in place of histamine h2 antagonists for gastroesophageal reflux. Gastric Acid Drugs
  • Antacids
  • Bile acid sequestrants Bile Acid Sequestrants Antidiarrheal Drugs
• ↑ Metabolism of glucocorticoids due to induction of CYP3A4 CYP3A4 Class 3 Antiarrhythmic Drugs (Potassium Channel Blockers):
  • Phenobarbital Phenobarbital A barbituric acid derivative that acts as a nonselective central nervous system depressant. It potentiates gamma-aminobutyric acid action on gaba-a receptors, and modulates chloride currents through receptor channels. It also inhibits glutamate induced depolarizations. First-Generation Anticonvulsant Drugs
  • Phenytoin Phenytoin An anticonvulsant that is used to treat a wide variety of seizures. The mechanism of therapeutic action is not clear, although several cellular actions have been described including effects on ion channels, active transport, and general membrane stabilization. Phenytoin has been proposed for several other therapeutic uses, but its use has been limited by its many adverse effects and interactions with other drugs. First-Generation Anticonvulsant Drugs
  • Rifampin Rifampin A semisynthetic antibiotic produced from streptomyces mediterranei. It has a broad antibacterial spectrum, including activity against several forms of Mycobacterium. In susceptible organisms it inhibits dna-dependent RNA polymerase activity by forming a stable complex with the enzyme. It thus suppresses the initiation of RNA synthesis. Rifampin is bactericidal, and acts on both intracellular and extracellular organisms. Epiglottitis
• ↓ Metabolism of glucocorticoids due to inhibition of CYP3A4 CYP3A4 Class 3 Antiarrhythmic Drugs (Potassium Channel Blockers):
  • Ritonavir Ritonavir An HIV protease inhibitor that works by interfering with the reproductive cycle of HIV. It also inhibits cytochrome p-450 cyp3a. Anti-HIV Drugs
  • Clarithromycin Clarithromycin A semisynthetic macrolide antibiotic derived from erythromycin that is active against a variety of microorganisms. It can inhibit protein synthesis in bacteria by reversibly binding to the 50s ribosomal subunits. This inhibits the translocation of aminoacyl transfer-RNA and prevents peptide chain elongation. Macrolides and Ketolides
  • Voriconazole Voriconazole A triazole antifungal agent that specifically inhibits sterol 14-alpha-demethylase and cytochrome p-450 cyp3a. Azoles
• Dosing adjustment may be necessary for antidiabetic agents.