Macrolides and Ketolides

Chemistry and Pharmacodynamics

Chemical structure

• Macrolides: characterized by a macrocyclic lactone ring Lactone Ring Polyenes
  • Ring contains 14‒16 atoms
  • 1 or more sugars are attached via glycosidic bonds
  • Erythromycin is the prototype drug of the class.
• Ketolides (e.g., telithromycin): similar structure to macrolides 
  • 14-atom ring
  • 1 of the sugars is substituted with a keto group
  • Derived from erythromycin

Mechanism of action

General:

• Inhibits bacterial protein synthesis Synthesis Polymerase Chain Reaction (PCR) by binding reversibly to the 50S ribosomal subunit   
  • Binds near the peptidyltransferase center → prevents peptidyl transferase Peptidyl Transferase Chloramphenicol from adding amino acids Amino acids Organic compounds that generally contain an amino (-NH2) and a carboxyl (-COOH) group. Twenty alpha-amino acids are the subunits which are polymerized to form proteins. Basics of Amino Acids to a growing peptide (prevents transpeptidation Transpeptidation Lincosamides)
  • Also inhibits the formation of the 50S subunit
• Limits bacterial growth → bacteriostatic Bacteriostatic Sulfonamides and Trimethoprim
• Additional effects:
  • Antiinflammatory effect by ↓ interleukins Interleukins Interleukins are a type of cytokines (signaling proteins) that communicate messages between different parts of the immune system. The majority of interleukins are synthesized by helper CD4 T lymphocytes along with other cells such as monocytes, macrophages, and endothelial cells. Interleukins and tumor Tumor Inflammation necrosis Necrosis The death of cells in an organ or tissue due to disease, injury or failure of the blood supply. Ischemic Cell Damage factor-alpha
  • Erythromycin is a motilin Motilin A peptide of about 22-amino acids isolated from the duodenum. At low ph it inhibits gastric motor activity, whereas at high ph it has a stimulating effect. Gastrointestinal Secretions receptor Receptor 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 agonist at duodenal enterochromaffin cells → has prokinetic properties

Fidaxomicin is an exception:

• Binds to RNA RNA A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. RNA Types and Structure polymerase → prevents RNA RNA A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. RNA Types and Structure 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
• Bactericidal Bactericidal Penicillins

Pharmacokinetics

Indications

Antimicrobial coverage

• Gram positive Gram positive Bacteria which retain the crystal violet stain when treated by gram’s method. Nocardia/Nocardiosis:
  • Streptococcus Streptococcus Streptococcus is one of the two medically important genera of gram-positive cocci, the other being Staphylococcus. Streptococci are identified as different species on blood agar on the basis of their hemolytic pattern and sensitivity to optochin and bacitracin. There are many pathogenic species of streptococci, including S. pyogenes, S. agalactiae, S. pneumoniae, and the viridans streptococci. Streptococcus
  • Staphylococcus Staphylococcus Staphylococcus is a medically important genera of Gram-positive, aerobic cocci. These bacteria form clusters resembling grapes on culture plates. Staphylococci are ubiquitous for humans, and many strains compose the normal skin flora. Staphylococcus
  • Clostridioides difficile (fidaxomicin)
• Gram negative Gram negative Bacteria which lose crystal violet stain but are stained pink when treated by gram’s method. Yersinia spp./Yersiniosis:
  • Escherichia coli Escherichia coli The gram-negative bacterium Escherichia coli is a key component of the human gut microbiota. Most strains of E. coli are avirulent, but occasionally they escape the GI tract, infecting the urinary tract and other sites. Less common strains of E. coli are able to cause disease within the GI tract, most commonly presenting as abdominal pain and diarrhea. Escherichia coli
  • Haemophilus influenzae Haemophilus Influenzae A species of Haemophilus found on the mucous membranes of humans and a variety of animals. The species is further divided into biotypes I through viii. Haemophilus and H. ducreyi
  • Moraxella catarrhalis Moraxella catarrhalis Gram-negative aerobic cocci of low virulence that colonize the nasopharynx and occasionally cause meningitis; bacteremia; empyema; pericarditis; and pneumonia. Moraxella
  • Salmonella Salmonella Salmonellae are gram-negative bacilli of the family Enterobacteriaceae. Salmonellae are flagellated, non-lactose-fermenting, and hydrogen sulfide-producing microbes. Salmonella enterica, the most common disease-causing species in humans, is further classified based on serotype as typhoidal (S. typhi and paratyphi) and nontyphoidal (S. enteritidis and typhimurium). Salmonella
  • Yersinia enterocolitica Yersinia enterocolitica A species of the genus yersinia, isolated from both man and animal. It is a frequent cause of bacterial gastroenteritis in children. Yersinia spp./Yersiniosis
  • Shigella Shigella Shigella is a genus of gram-negative, non-lactose-fermenting facultative intracellular bacilli. Infection spreads most commonly via person-to-person contact or through contaminated food and water. Humans are the only known reservoir. Shigella
  • Campylobacter jejuni Campylobacter jejuni A species of bacteria that resemble small tightly coiled spirals. Its organisms are known to cause abortion in sheep and fever and enteritis in man and may be associated with enteric diseases of calves, lambs, and other animals. Campylobacter
  • Vibrio cholerae Vibrio cholerae The etiologic agent of cholera. Vibrio
  • Neisseria gonorrhoeae Neisseria gonorrhoeae A species of gram-negative, aerobic bacteria primarily found in purulent venereal discharges. It is the causative agent of gonorrhea. Neisseria
  • Helicobacter pylori Helicobacter pylori A spiral bacterium active as a human gastric pathogen. It is a gram-negative, urease-positive, curved or slightly spiral organism initially isolated in 1982 from patients with lesions of gastritis or peptic ulcers in Western Australia. Helicobacter pylori was originally classified in the genus campylobacter, but RNA sequencing, cellular fatty acid profiles, growth patterns, and other taxonomic characteristics indicate that the micro-organism should be included in the genus Helicobacter. It has been officially transferred to Helicobacter gen. Helicobacter
  • Bordetella pertussis Bordetella pertussis A species of gram-negative, aerobic bacteria that is the causative agent of whooping cough. Its cells are minute coccobacilli that are surrounded by a slime sheath. Bordetella
• Atypical:
  • Mycoplasma pneumoniae Mycoplasma pneumoniae Short filamentous organism of the genus mycoplasma, which binds firmly to the cells of the respiratory epithelium. It is one of the etiologic agents of non-viral primary atypical pneumonia in man. Mycoplasma
  • Chlamydia pneumoniae Chlamydia pneumoniae A species of chlamydophila that causes acute respiratory infection, especially atypical pneumonia, in humans, horses, and koalas. Chlamydia
  • Legionella pneumophila Legionella pneumophila A species of gram-negative, aerobic bacteria that is the causative agent of legionnaires’ disease. It has been isolated from numerous environmental sites as well as from human lung tissue, respiratory secretions, and blood. Legionella/Legionellosis
  • Treponema pallidum Treponema pallidum The causative agent of venereal and non-venereal syphilis as well as yaws. Treponema
  • Babesia Babesia Babesiosis is an infection caused by a protozoa belonging to the genus, Babesia. The most common Babesia seen in the United States is B. microti, which is transmitted by the Ixodes tick. The protozoa thrive and replicate within host erythrocytes. Lysis of erythrocytes and the body’s immune response result in clinical symptoms. Babesia/Babesiosis microti
  • Ureaplasma
• Mycobacterium avium Mycobacterium avium A bacterium causing tuberculosis in domestic fowl and other birds. In pigs, it may cause localized and sometimes disseminated disease. The organism occurs occasionally in sheep and cattle. It should be distinguished from the m. avium complex, which infects primarily humans. Mycobacterium complex (MAC)

Types of infection

• Respiratory 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:
  • Community-acquired pneumonia Community-Acquired Pneumonia Pneumonia in Children
  • MAC prophylaxis Prophylaxis Cephalosporins and treatment
  • Legionnaire disease
  • Pertussis Pertussis Pertussis, or whooping cough, is a potentially life-threatening highly contagious bacterial infection of the respiratory tract caused by Bordetella pertussis. The disease has 3 clinical stages, the second and third of which are characterized by an intense paroxysmal cough, an inspiratory whoop, and post-tussive vomiting. Pertussis (Whooping Cough)
  • Streptococcal pharyngitis Streptococcal Pharyngitis Rheumatic Fever
• Sexually transmitted 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:
  • Gonorrhea Gonorrhea Gonorrhea is a sexually transmitted infection (STI) caused by the gram-negative bacteria Neisseria gonorrhoeae (N. gonorrhoeae). Gonorrhea may be asymptomatic but commonly manifests as cervicitis or urethritis with less common presentations such as proctitis, conjunctivitis, or pharyngitis. Gonorrhea
  • Chlamydia Chlamydia Chlamydiae are obligate intracellular gram-negative bacteria. They lack a peptidoglycan layer and are best visualized using Giemsa stain. The family of Chlamydiaceae comprises 3 pathogens that can infect humans: Chlamydia trachomatis, Chlamydia psittaci, and Chlamydia pneumoniae. Chlamydia
  • Chancroid Chancroid Chancroid is a highly transmissible STD caused by Haemophilus ducreyi. The disease presents with painful ulcer(s) on the genital tract (termed chancroid or “soft chancre”). Up to 50% of patients will develop painful inguinal lymphadenopathy. Chancroid
• H. pylori H. pylori A spiral bacterium active as a human gastric pathogen. It is a gram-negative, urease-positive, curved or slightly spiral organism initially isolated in 1982 from patients with lesions of gastritis or peptic ulcers in Western Australia. Helicobacter pylori was originally classified in the genus campylobacter, but RNA sequencing, cellular fatty acid profiles, growth patterns, and other taxonomic characteristics indicate that the micro-organism should be included in the genus Helicobacter. It has been officially transferred to Helicobacter gen. Helicobacter infection (clarithromycin is part of triple therapy)
• C. difficile-associated diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea (fidaxomicin is monotherapy)
• 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 and soft tissue Soft Tissue Soft Tissue Abscess 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: acne

Other indications

• Chronic obstructive pulmonary disease Pulmonary disease Diseases involving the respiratory system. Blastomyces/Blastomycosis and cystic Cystic Fibrocystic Change fibrosis Fibrosis Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury. Bronchiolitis Obliterans exacerbations (anti-inflammatory effect)
• Gastroparesis Gastroparesis Chronic delayed gastric emptying. Gastroparesis may be caused by motor dysfunction or paralysis of stomach muscles or may be associated with other systemic diseases such as diabetes mellitus. Malabsorption and Maldigestion (erythromycin, promotility effect)

Ketolide indications

• Similar antimicrobial activity as macrolides
• Telithromycin was discontinued in the United States (previously only indicated for community-acquired pneumonia Community-Acquired Pneumonia Pneumonia in Children).

Adverse Effects and Contraindications

Macrolides

• Adverse effects:
  • GI upset (especially with erythromycin and fidaxomicin)
  • Dizziness Dizziness An imprecise term which may refer to a sense of spatial disorientation, motion of the environment, or lightheadedness. Lateral Medullary Syndrome (Wallenberg Syndrome)
  • Hepatotoxicity Hepatotoxicity Acetaminophen:
    • Abnormal liver function tests Liver function tests Liver function tests, also known as hepatic function panels, are one of the most commonly performed screening blood tests. Such tests are also used to detect, evaluate, and monitor acute and chronic liver diseases. Liver Function Tests
    • Hepatitis
    • Cholestatic jaundice Jaundice Jaundice is the abnormal yellowing of the skin and/or sclera caused by the accumulation of bilirubin. Hyperbilirubinemia is caused by either an increase in bilirubin production or a decrease in the hepatic uptake, conjugation, or excretion of bilirubin. Jaundice
    • Hepatic necrosis Necrosis The death of cells in an organ or tissue due to disease, injury or failure of the blood supply. Ischemic Cell Damage
    • Hepatic failure Hepatic failure Severe inability of the liver to perform its normal metabolic functions, as evidenced by severe jaundice and abnormal serum levels of ammonia; bilirubin; alkaline phosphatase; aspartate aminotransferase; lactate dehydrogenases; and albumin/globulin ratio. Autoimmune Hepatitis
  • QT prolongation
• 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: history of hepatic impairment or cholestatic jaundice Jaundice Jaundice is the abnormal yellowing of the skin and/or sclera caused by the accumulation of bilirubin. Hyperbilirubinemia is caused by either an increase in bilirubin production or a decrease in the hepatic uptake, conjugation, or excretion of bilirubin. Jaundice
• Warnings:
  • Altered cardiac conduction (especially those with QT prolongation and electrolyte abnormalities) 
  • Hepatotoxicity Hepatotoxicity Acetaminophen 
  • Myasthenia gravis Myasthenia Gravis Myasthenia gravis (MG) is an autoimmune neuromuscular disorder characterized by weakness and fatigability of skeletal muscles caused by dysfunction/destruction of acetylcholine receptors at the neuromuscular junction. MG presents with fatigue, ptosis, diplopia, dysphagia, respiratory difficulties, and progressive weakness in the limbs, leading to difficulty in movement. Myasthenia Gravis exacerbation
  • Clarithromycin: potential ↑ mortality Mortality All deaths reported in a given population. Measures of Health Status in patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with coronary artery Coronary Artery Truncus Arteriosus disease  
• Drug interactions (particularly with erythromycin and clarithromycin due to CYP3A4 CYP3A4 Class 3 Antiarrhythmic Drugs (Potassium Channel Blockers) inhibition):
  • Warfarin Warfarin An anticoagulant that acts by inhibiting the synthesis of vitamin K-dependent coagulation factors. Warfarin is indicated for the prophylaxis and/or treatment of venous thrombosis and its extension, pulmonary embolism, and atrial fibrillation with embolization. It is also used as an adjunct in the prophylaxis of systemic embolism after myocardial infarction. Warfarin is also used as a rodenticide. Anticoagulants: ↑ INR
  • Simvastatin Simvastatin A derivative of lovastatin and potent competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme a reductase, which is the rate-limiting enzyme in cholesterol biosynthesis. It may also interfere with steroid hormone production. Due to the induction of hepatic ldl receptors, it increases breakdown of ldl cholesterol. Statins, lovastatin Lovastatin A fungal metabolite isolated from cultures of aspergillus terreus. The compound is a potent anticholesteremic agent. It inhibits 3-hydroxy-3-methylglutaryl coenzyme a reductase, which is the rate-limiting enzyme in cholesterol biosynthesis. It also stimulates the production of low-density lipoprotein receptors in the liver. Statins: ↑ risk of myalgia Myalgia Painful sensation in the muscles. Ion Channel Myopathy and/or rhabdomyolysis Rhabdomyolysis Rhabdomyolysis is characterized by muscle necrosis and the release of toxic intracellular contents, especially myoglobin, into the circulation. Rhabdomyolysis
  • Midazolam Midazolam A short-acting hypnotic-sedative drug with anxiolytic and amnestic properties. It is used in dentistry, cardiac surgery, endoscopic procedures, as preanesthetic medication, and as an adjunct to local anesthesia. The short duration and cardiorespiratory stability makes it useful in poor-risk, elderly, and cardiac patients. It is water-soluble at ph less than 4 and lipid-soluble at physiological pH. Benzodiazepines: somnolence
  • Theophylline Theophylline A methyl xanthine derivative from tea with diuretic, smooth muscle relaxant, bronchial dilation, cardiac and central nervous system stimulant activities. Theophylline inhibits the 3. Asthma Drugs: seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures
  • ↑ Serum concentrations of:
    • Tacrolimus Tacrolimus A macrolide isolated from the culture broth of a strain of streptomyces tsukubaensis that has strong immunosuppressive activity in vivo and prevents the activation of T-lymphocytes in response to antigenic or mitogenic stimulation in vitro. Immunosuppressants 
    • Cyclosporine Cyclosporine A cyclic undecapeptide from an extract of soil fungi. It is a powerful immunosupressant with a specific action on T-lymphocytes. It is used for the prophylaxis of graft rejection in organ and tissue transplantation. Immunosuppressants
    • Ergot alkaloids Ergot alkaloids Alkaloids originally isolated from the ergot fungus claviceps purpurea (hypocreaceae). They include compounds that are structurally related to ergoline (ergolines) and ergotamine (ergotamines). Many of the ergot alkaloids act as alpha-adrenergic antagonists. Triptans and Ergot Alkaloids 
    • Colchicine Colchicine A major alkaloid from colchicum autumnale l. And found also in other colchicum species. Its primary therapeutic use is in the treatment of gout. Gout Drugs

Ketolides

• Adverse effects:
  • GI upset
  • Visual disturbance
  • Hepatotoxicity Hepatotoxicity Acetaminophen
  • Syncope Syncope Syncope is a short-term loss of consciousness and loss of postural stability followed by spontaneous return of consciousness to the previous neurologic baseline without the need for resuscitation. The condition is caused by transient interruption of cerebral blood flow that may be benign or related to a underlying life-threatening condition. Syncope
• 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:
  • Hypersensitivity to macrolide antibiotics
  • Myasthenia gravis Myasthenia Gravis Myasthenia gravis (MG) is an autoimmune neuromuscular disorder characterized by weakness and fatigability of skeletal muscles caused by dysfunction/destruction of acetylcholine receptors at the neuromuscular junction. MG presents with fatigue, ptosis, diplopia, dysphagia, respiratory difficulties, and progressive weakness in the limbs, leading to difficulty in movement. Myasthenia Gravis
  • Hepatitis or jaundice Jaundice Jaundice is the abnormal yellowing of the skin and/or sclera caused by the accumulation of bilirubin. Hyperbilirubinemia is caused by either an increase in bilirubin production or a decrease in the hepatic uptake, conjugation, or excretion of bilirubin. Jaundice
• Warnings:
  • Hepatotoxicity Hepatotoxicity Acetaminophen
  • Myasthenia gravis Myasthenia Gravis Myasthenia gravis (MG) is an autoimmune neuromuscular disorder characterized by weakness and fatigability of skeletal muscles caused by dysfunction/destruction of acetylcholine receptors at the neuromuscular junction. MG presents with fatigue, ptosis, diplopia, dysphagia, respiratory difficulties, and progressive weakness in the limbs, leading to difficulty in movement. Myasthenia Gravis exacerbation
  • QT prolongation

Mechanism of Resistance

There are 3 methods of resistance Resistance Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow. Ventilation: Mechanics of Breathing to macrolides:

• Ribosomal methylation Methylation Addition of methyl groups. In histo-chemistry methylation is used to esterify carboxyl groups and remove sulfate groups by treating tissue sections with hot methanol in the presence of hydrochloric acid. . Glucocorticoids or mutation Mutation Genetic mutations are errors in DNA that can cause protein misfolding and dysfunction. There are various types of mutations, including chromosomal, point, frameshift, and expansion mutations. Types of Mutations:
  • Prevents macrolide binding
  • Can be either plasmid mediated or chromosomal
• Production of drug-inactivating enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes:
  • Esterases
  • Kinases 
• Production of active ATP-dependent efflux proteins Proteins Linear polypeptides that are synthesized on ribosomes and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of amino acids determines the shape the polypeptide will take, during protein folding, and the function of the protein. Energy Homeostasis: 
  • Transport the drug outside the cell
  • Ketolides are not affected by this resistance Resistance Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow. Ventilation: Mechanics of Breathing mechanism → allows for their use in some macrolide-resistant strains

Comparison of Medications