3B : ANTI-BACTERIAL Flashcards
Substance, produced by one microorganism, or produced partly or wholly through synthetic means, which at low concentrations can inhibit the growth of, or are lethal to other microorganisms
Antibiotic
- first antibiotic
- discovered in September 1928 by an English Bacteriologist, late Sir Alexander Fleming
- accidentally obtained the antibiotic from a soil -inhabiting fungusPenicillium notatum
Penicillin
kill bacteria
Bactericidal
inhibit bacterial growth
Bacteriostatic
CHARACTERISTICS OF ANTIBIOTICS
- Kill or inhibit the growth of pathogens
- Cause no allergic reaction to host cell
- Don’t cause damage to host cell
- Should be stable when stored in liquid or solid form
HOW CLASSIFICATION OF ANTIBIOTICS BEING MADE
Classification according to
* Chemical or molecular structure
* Mechanism of action
* Spectrum of activity
* Absorbability from site of administration
Antibiotics within the same structural class will generally show similar pattern of
- Effectiveness
- Toxicity
- Allergic potential side effects
CLASSIFICATIONS ACCORDING TO MECHANISM
INHIBITION OF CELL WALL SYNTHESIS
INHIBITION OF PROTEIN SYNTHESIS
INHIBITION OF BACTERIAL METABOLISM
INHIBITION OF NUCLEIC ACID SYNTHESIS
DISRUPTION OF PLASMA MEMBRANE
ANTIBIOTICS UNDER INHIBITORS OF CELL WALL SYNTHESIS
- β-Lactams
- Glycopeptide
- Other Inhibitors of Cell Wall Synthesis
INHIBITION OF CELL WALL SYNTHESIS ANTIBIOTICS under β-Lactams
- Penicillins
- Cephalosporins
- Carbapenems
- Monobactams
INHIBITION OF CELL WALL SYNTHESIS ANTIBIOTICS under Glycopeptides
Vancomycin
INHIBITION OF CELL WALL SYNTHESIS ANTIBIOTICS under Other Inhibitors of Cell Wall Synthesis
- Bacitracin
- Cycloserine
- Daptomycin
- Fosfomycin
INHIBITION OF PROTEIN SYNTHESIS ANTIBIOTICS under 30S
- Aminoglycosides
- Tetracyclines
INHIBITION OF PROTEIN SYNTHESIS ANTIBIOTICS under 50S
- Chloramphenicol
- Macrolides
- Lincosamides
- Oxazolidinone
INHIBITION OF BACTERIAL METABOLISM ANTIBIOTICS under FOLIC ACID SYNTHESIS
- Sulfonamides
- Trimethoprim
INHIBITION OF BACTERIAL METABOLISM ANTIBIOTICS under MYCOLIC ACID SYNTHESIS
Isoniazid
INHIBITION OF NUCLEIC ACID SYNTHESIS under DNA Synthesis
- Fluoroquinolones
- Metronidazole
INHIBITION OF NUCLEIC ACID SYNTHESIS under RNA Synthesis
- Rifamycins
Antibiotics with action of Disrupting the plasma membrane
- Polymyxin
- Mupirocin
- Contain the beta-lactam ring
- Inhibit bacterial cell wall biosynthesis- bactericidal
- Modifications of the R- group side-chain (attached to the β-lactam ring) alter the pharmacologic properties and resistance to β- lactamase
BETA LACTAMS
Drug classes under beta lactams
- PENICILLINS
- CEPHALOSPORINS
- MONOBACTAMS
- CARBAPENEMS
Inactivate bacterial transpeptidases and prevent the cross-linking of peptidoglycan polymers which is essential for bacterial cell wall integrity. This results in a loss of rigidity and susceptibility to rupture.
PENICILLINS
bind to and inactivate penicillin-binding proteins (PBPs) involved in cell wall synthesis. The action of autolysinin the presence of penicillin further weakens the cell wall.
PENICILLINS
Gram-positive or gram negative bacteria with thick external cell walls are particularly susceptible to penicillin?
Gram-positive
The major cause of resistance for penicillin is?
the production of the β- lactamases (penicillinases).
Common organisms capable of producing penicillinase
- Staphylococcus aureus,
- Escherichia coli,
- Pseudomonas aeruginosa,
- Neisseria gonorrhoeae, and
- Bacillus,
- Proteus, and
- Bacteroides species.
Resistance to penicillin may also occur because
- bacteria lack receptors or other PBPs, are impermeable to penicillins, lack cell walls, or are metabolically inactive.
Narrow-spectrum against gram-positive and a few gram-negative bacteria
Natural Penicillins
drugs under natural Penicillins
Penicillin G
Penicillin V
Penicillinase Resistant. Narrow-spectrum against gram-positive bacteria only, including strains producing penicillinase
Semisynthetic Penicillins
drugs under semisynthetic penicillin
Methicillin
Nafcillin,
Oxacillin,
Dicloxacillin
Narrow-spectrum against gram-positive bacteria but with an increased gram-negative spectrum
Extended Penicillin
what are the groups under extended penicillins
- Aminopenicillins
- Anti-pseudomonal Penicillins
group under anti pseudomonal penicillins
- Ureidopenicillins
- Carboxypenicillins
drugs under Ureidopenicillins
Piperacillin
Mezlocillin
Azlocillin
drugs under carboxypenicillin
Carbenicillin
Ticarcillin
Temocillin
Pharmacologic properties of penicillin
- Penicillins are absorbed rapidly after enteral administration, although erratically, and parenteral administration and are distributed throughout body fluids;
- they penetrate the cerebrospinal fluid (CSF) and ocular fluid significantly only during inflammation.
- Gastrointestinal (GI) absorption may be decreased in the presence of food.
drugs under pen G
Benzylpenicillin
PEN G
IV or ORAL?
- Given by injection into a vein or muscle
-
Long-acting forms are given by IM route:
Penicillin G Benzathine
Penicillin G Procaine
Spectrum of activity of Pen G
- Aerobes
- Gram-positive cocci
- Gram-positive rods, e.g., Bacillus spp, Listeria spp, Clostridium
- Gram-negative, e.g., Gonococci, Meningococci
- Anaerobes
Most, except Bacillus fragilis - Others: Treponema pallidum, Leptospira spp
Suspensions of penicillin G that prolong its half-life ( 30 min), allowing a reduced frequency of injections
A uricosuric agent that blocks renal secretion of penicillin, is used for this purpose, but only rarely.
Probenecid
An oral form of Pen G with poor bioavailability, has a narrower spectrum of activity
Penicillin V
used predominantly for penicillinase-producing staphylococcal infections
Penicillinase- Resistant Penicillins
Used of these agents, which are administered orally, is declining due to the increased incidence of methicillin-resistant S. aureus (MRSA) that also confers resistance to cephalosporins.
inactivated by β- lactamases
Have a broadened gram-negative coverage.
Resistance has become a more common problem
Extended-Spectrum Penicillins
What are the drugs under Extended-Spectrum Penicillins
- Aminopenicillins
- Ureidopenicillins
- Carboxypenicillins
drugs under Aminopenicillins
Ampicillin
Amoxicillin
Bacampicillin
IV injections must be given slowly, as rapid IV injections can lead to convulsive seizures
Ampicillin
Useful in infections caused by Haemophilus influenzae, Streptococcus pneumonia, Streptococcus pyrogenses, Neisseria meningitidis, Proteus mirabilis, Enterococcus faecalis, E. coli, Proteus mirabilis, Salmonella enterica, and Shigella
Ampicillin
consideration on giving ampicillin
- Large doses of ampicillin can increase the risk of bleeding with concurrent use of warfarin and other oral anticoagulants, possibly by inhibiting platelet aggregation
- When administered separately, aminoglycosides and ampicillin can potentiate each other
similar to ampicillin but has better oral absorption.
Amoxicillin
Prodrug of ampicillin with improved oral bioavailability
Bacampicillin
- not absorbed orally, and must therefore be given by intravenous or intramuscular injection
- Enhanced penetration into gram-negative bacteria and reduced susceptibility to cleavage by gram-negative beta lactamase enzymes
- These properties confer activity against the important hospital pathogen Pseudomonas aeruginosa. Sometimes referred to as an “anti-pseudomonal penicillin“
- When used alone, lacks strong activity against the gram-positive pathogens
Piperacillin
- Active against both Gram-negative including Pseudomonas aeruginosa and some Gram-positive bacteria
- Unlike most other extended spectrum penicillins, it is excreted by the liver, therefore it is useful for biliary tract infections
Mezlocillin
- Given orally, parenterally
- Has Gram-negative coverage which includes Pseudomonas aeruginosa but limited Gram-positive coverage
- At high doses can cause bleeding
- Can cause hypokalemia by promoting potassium loss at the distal convoluted tubule of the kidney
Carbenicillin
- Not absorbed orally, so must be given by intravenous or intramuscular injection
- Main clinical use is as an injectable antibiotic for the treatment of Gram-negative bacteria, particularly Pseudomonas aeruginosa
Ticarcillin
Adverse Effects of Penicillin
- hypersensitivity (All reactions, from a simple rash to anaphylaxis, can be observed within two minutes or up to 3 days following administration)
- adverse effect results from direct irritation or pain on injection, GI upset, or superinfection.
- also have β- lactam ring. Substitutions at R1 determine antibacterial activity. Substitution at R2 determines pharmacokinetics.
Cephalosporins
selected agents of Cephalosporins
penetrate CSF.
- cefuroxime, 2nd generation
- cefotaxime, and
- ceftizoxime
- newer generation of cephalosporins is increasingly resistant to penicillinases.
- categorized by their antibacterial spectrum, especially against Gram-negative organisms
cephalosporinss
First Generation Cephalosporins
Cefacetrile
Cefadroxil
Cefalexin
Cefaloglycin
Cefalonium
Cefaloridine
Cefalotin
Cefapirin
Cefatrizine
Cefazaflur
Cefazedone
Cefazolin
Cefradine
Cefroxadine
Ceftezole
1st generation cephalosporin have activity against
- some gram- positive organisms (streptococci) and
- some gram- negative organisms
- Proteus mirabilis,
- Escherichia coli
- Klebsiella infections (PEcK), and
- penicillin-and-sulfonamide-resistant urinary tract infections
Prophylaxis in various surgical procedures
These agents do not penetrate CSF
Second Generation Cephalosporin
- Cefaclor
- Cefonicid
- Cefprozil
- Cefuroxime
- Cefuzonam
Antianaerobe activity of second generation
- Cefmetazole
- Cefotetan
- Cefoxitin
The following cephems are also sometimes grouped with second-generation cephalosporins
Carbacephems:
* Loracarbef
Cephamycins:
* Cefbuperazone
* Cefmetazole
* Cefminox
* Cefotetan
* Cefoxitin
* Cefotiam
second generation cephalosporins
They are used in the treatment of
- streptococcal infections as well as infections caused by E. coli, Klebsiella, and Proteus spp.
- Most anaerobes (except Clostridium difficile)
- Used primarily in managing urinary and respiratory tract, bone, and soft tissue infections and prophylactically in various surgical procedures
Third Generation cephalosporins
Cefcapene
Cefdaloxime
Cefdinir
Cefditoren
Cefetamet
Cefixime
Cefmenoxime
Cefodizime
Cefotaxime
Cefovecin
Cefpimizole
Cefpodoxime
Cefteram
Ceftamere
Ceftibuten
Ceftiofur
Ceftiolene
Ceftizoxime
Ceftriaxone
Antipseudomonal activity of second generation cephalosporin:
- Cefoperazone
- Ceftazidime
These cephems are also sometimes grouped with third-generation cephalosporins:
Oxacephems:
Latamoxef
Uses for third generation cephalosporin
- enhanced activity against gram-negative organisms
- against H. influenzae, N. gonorrhoeae, N. meningitides, Enterobacter, Salmonella, indole-positive Proteus, Serratia spp., and E. coli and moderate activity against anaerobes.
- Serious hospital-acquired gram-negative infections, alone or in combination with an aminoglycoside
- Cefoperazone and ceftazidimehave excellent activity against P. aeruginosa.
is used for sexually transmitted infections caused by gonorrhea, as well as in empiric therapy for community-acquired meningitis.
Ceftriaxone
, third-generation- cephalosporins penetrate the CSF. except
for cefoperazone
third generation cephalosporin which are excreted through the biliary tract, thus enabling the use of these agents for infections of the biliary tree.
cefoperazone and ceftriaxone,
also Mezlocillin (but not under cephalosporins)
Fourth Generation cephalosporins
Cefclidine
Cefepime
Cefluprenam
Cefoselis
Cefozopran
Cefpirome
These cephems are also sometimes grouped with fourth-generation cephalosporins:
Oxacephems:
* Flomoxef
4th generation cephalosporins that has powerful coverage against Pseudomonas spp., as well as other gram-positive and gram-negative bacteria
Cefepime
4th generation cephalosporins have
- a greater resistance to β-lactamases than the third-generation cephalosporins
- Many can cross the blood-brain barrier and are effective in meningitis
5th-generation cephalosporins
- Ceftaroline,
- Ceftobiprole,
- Ceftolozane
Fifth-generation are Active against
- Methicillin-resistantS. aureus(MRSA)
- Penicillin-resistant streptococci
- Ampicillin-susceptible and beta-lactamase–producingEnterococcus faecalis
5th generation cephalosporins that Has powerful antipseudomonal characteristics and appears to be less susceptible to the development of resistance
Ceftobiprole
5th generation cephalosporins that
* Does not have the antipseudomonal coverage
* Has MRSA coverage
Ceftaroline
5th generation
- New option for treatment of Complicated Intra-abdominal Infections (cIAI), and Complicated Urinary Tract Infections (cUTI)
- Combined with the β-lactamase inhibitor tazobactam
Ceftolozane
adverse effects of cephalosporins
- Hypersensitivity reactions including urticaria, fever, joint pains, rashes, angioedema, anaphylaxis, serum sickness-like reaction
- Penicillin/cephalosporin allergic cross-reactivity
- Rarely CNS toxicity, including convulsions (especially with high doses or in severe renal impairment), interstitial nephritis, hemolytic anemia, leukopenia, thrombocytopenia, and coagulation disorders
- Alcohol intolerance (disulfiram-like) is seen with cefamandole and ceftriaxone
- Cephalosporins may cause bleeding disorders; nephrotoxicity when administered with diuretics
- Also reported diarrhea (including antibiotic-associated colitis).
- May cause superinfection with gram-positive organisms or fungi.
are the number one cause of hospital-acquired C. difficile colitis, a potentially life-threatening infection.
Cephalosporins
only commercially available monobactam antibiotic
AZTREONAM
- a naturally occurring monobactam lacking the thiazolidine ring that is highly resistant to β- lactamases
- Poorly absorbed when given orally, so it must be administered as an intravenous or intramuscular injection
- Has good activity against gram-negative organisms, but it lacks activity against anaerobes and gram-positive organisms.
- Useful for various types of infections caused by E. coli, Klebsiella pneumonia, H. influenzae, P. aeruginosa, Enterobacter spp., Citrobacter spp., and P. mirabilis.
AZTREONAM
Demonstrates no cross-reactivity with penicillins or cephalosporins for hypersensitivity reactions
AZTREONAM
Generally, exhibit good activity against anaerobes such as Bacteroides fragilis
This class of antibiotics is usually reserved for known or suspected multidrug-resistant (MDR) bacterial infections
Useful for infections caused by penicillinase-producing S. aureus, E. coli, Klebsiella spp., Enterobacter spp., and H. influenzae, among others.
CARBAPENEMS
- are powerful agents used for Pseudomonas infections
- Exhibit good activity against anaerobes such as Bacteroides fragilis
CARBAPENEMS
- are powerful agents used for Pseudomonas infections
- Exhibit good activity against anaerobes such as Bacteroides fragilis
CARBAPENEMS
side effect of CARBAPENEMS
- Nausea, vomiting, diarrhea, skin rashes, and
- at higher doses, seizures are their most common adverse effects, particularly for imipenem.
Hydrolyzed in the mammalian kidney by a dehydropeptidase enzyme to a nephrotoxic intermediate, and thus is co-formulated with the dehydropeptidase inhibitor cilastatin
Imipenem
- Stable to mammalian dehydropeptidases and does not require co-administration of cilastatin
- Somewhat less potent than imipenem against gram-positive pathogens, and somewhat more potent against gram-negative infections
- Unlike imipenem, which produced an unacceptable rate of seizures in a phase 2 trial, ____ is effective for the treatment of bacterial meningitis
Meropenem
Lacks useful activity against the P. aeruginosa and Acinetobacter species, both of which are important causes of hospital-acquired infections
Ertapenem
Occurs as a result of the expression of one of many genes for the production of β-lactamases, a class of enzymes that breaks open the β-lactam ring
BACTERIAL RESISTANCE TO BETA-LACTAM
Bacteria that can produce beta-lactamases include, but are not limited to:
Staphylococcus
* MRSA (Methicillin-resistant Staphylococcus aureus)
Enterobacteriaceae:
* Klebsiella pneumoniae
* Citrobacter
* Proteus vulgaris
* Morganella
* Salmonella
* Shigella
* Escherichia coli
Haemophilus influenzae
Neisseria gonorrhoeae
Pseudomonas aeruginosa
Mycobacterium tuberculosis
To overcome this resistance, β-lactam antibiotics are often given with β-lactamase inhibitors such as
- Clavulanic acid or clavulanate
- Sulbactam
- Tazobactam
MOA of β-lactamase inhibitors
Act as suicide substrates which ultimately leads to the degradation of the beta-lactamase
durgs under Clavulanic acid or clavulanate
- Amoxicillin + Clavulanic acid (Co-amoxiclav)
- Ticarcillin + Clavulanic acid (Co-ticarclav)
drugs under Sulbactam
Ampicillin + Sulbactam
drug under Tazobactam
Piperacillin + Tazobactam
- No antimicrobial property
- Irreversibly inhibits β- lactamase; when administered with penicillins,
- exposes penicillinase-producing organisms to therapeutic concentrations of penicillin.
Clavulanic acid
- Clavulanic acid Used in combination products amoxicillin/clavulanic acid and ticarcillin/clavulanic acid for administration
co-amoxiclav
co-ticarclav
oral and parenteral
DRUGS UNDER OTHER INHIBITORS OF CELL WALL SYNTHESIS
- VANCOMYCIN
- BACITRACIN
- CYCLOSERINE
- DAPTOMYCIN
- FOSFOMYCIN
MOA:
Binds to the terminal end of the peptidoglycan to prevent further elongation and cross-linking due to inhibition of transglycosylase; this results in decreased cell membrane activity and increased cell lysis.
VANCOMYCIN
THERAPEUTIC USE OF VANCOMYCIN
- Active against gram-positive organisms; resistant strains have been reported.
- Used in serious MRSA infections, in patients allergic to penicillins and cephalosporins, and to treat antibiotic-associated enterocolitis (C. difficile colitis).
- Penetrates CSF only during inflammation
Rapid infusion of vancomycin may cause
anaphylactoid reactions and “redneck” syndrome (flushing caused by the release of histamine).
Rarely, high levels of vancomycin may cause
ototoxicity with permanent auditory impairment and nephrotoxicity
VANCOMYCIN INDICATION
- A variety of dosage forms (for example, oral, injections, etc.) exist for **treating serious or severe infections caused by susceptible strains of methicillin-resistant (beta-lactam-resistant) staphylococci. **
- Additionally, a unique FDA-approved oral liquid treatment is also available and indicated for the treatment of Clostridium difficile-associated diarrhea and enterocolitis caused by Staphylococcus aureus, including methicillin-resistant strains.
inhibits dephosphorylation and reuse of the phospholipid required for acceptance of N- acetylmuramic acid pentapeptide, the building block of the peptidoglycan complex.
BACITRACIN
USES OF BACITRACIN
- Most active against gram-positive bacteria.
- Used only topically in combination with neomycin or polymyxin for minor infections
- As a polypeptide, toxic, and difficult-to-use chemical, bacitracin doesn’t work well orally; however, it is very effective topically
- Used in ointment form for topical treatment of a variety of localized skin and eye infections, as well as for the prevention of wound infections
inhibits alanine racemase and the incorporation of alanine into the peptidoglycan pentapeptide.
Cycloserine
- is active against mycobacteria and gram-negative bacteria.
agent is used only as a second-line drug for treating urinary tract infections and tuberculosis (TB)
CYCLOSERINE
At high doses, cycloserine may cause
severe central nervous system (CNS) toxicity, including seizures and acute psychosis
a bactericidal agent that binds to and depolarizes the cell membrane, resulting in loss of membrane potential and rapid cell death.
DAPTOMYCIN
- Has antibacterial actions similar to that of vancomycin
- Active in vancomycin-resistant strains
- May cause myopathy.
DAPTOMYCIN
inhibits the enzyme enolpyruvate transferase and thereby interferes downstream with the bacterial cell wall-specific N-acetylmuramic acid.
FOSFOMYCIN
This oral agent is active against both gram-negative organisms. It is used to treat simple lower urinary tract infections.
FOSFOMYCIN
drugs under AMINOGLYCOSIDES
Gentamicin
Tobramycin
Amikacin
Kanamycin
Neomycin
Netilmicin
Streptomycin
Mechanism of Action of aminoglycosides
- inhibit bacterial protein synthesis; they are bactericidal against most gram-negative aerobic bacteria.
- Aminoglycosides passively diffuse via porin channels through the outer membrane of gram-negative aerobic bacteria. Transport across the inner membrane requires active uptake that is dependent on electron transport (gram-negative aerobes only), the so-called energy-dependent phase I transport.
- Inside the cell, these agents interact with the receptor proteins on the 30S ribosomal subunit. This “freezes” the initiation complex and leads to a buildup of monosomes; it also causes translation errors.
how can resistance to aminoglycosides develop?
- Resistance generally results from bacterial enzymes that inactivate the drugs
- It may occur through 3 separate mechanisms:
- DECREASED UPTAKE - due to the absence of oxygen-dependent permeases; only in anaerobic bacteria (only aerobic bacteria have oxygen-dependent permeases)
- DECREASED AFFINITY – due to structural alterations of the 30S subunit
- INCREASED INACTIVATION– due to the presence of aminoglycoside-inactivating enzymes which modify the aminoglycosides, thus inactivating them – these enzymes include acetyltransferases, nucleotidyltransferases, and phosphotransferases
Anaerobic bacteria are generally resistant to aminoglycosides
true or false and why?
true
- Some bacteria use an oxygen-dependent transport system to bring the amino-glycosides into the cell.
- The anaerobes (with non–oxygen-based metabolism) do not have this system. Therefore, they are generally resistant to the aminoglycosides
Aminoglycosides are poorly absorbed from the GI tract. Most aminoglycosides must be administered parenterally
true or false
true
- Aminoglycosides agents do not penetrate the CSF.
- They are highly polar compounds and are relatively insoluble in fat.
- They do not readily penetrate most cells without help from penicillin or a transport system.
what is the solution?
Synergism between penicillins and aminoglycosides - The penicillins cause cell wall abnormalities that allow the aminoglycosides to gain entry into the bacteria
- administered intramuscularly and/or IV
- may cross the placental barrier
- may not cross the blood-brain barrier
STREPTOMYCIN
treatment of tularemia due to francisella infection
STREPTOMYCIN
medical uses of streptomycin
- treatment of pneumonia due to enterobacter, proteus, klebsiella and/or pseudomonas infection
- treatment of cystitis due to escherichia, enterobacter, proteus and/or klebsiella infection
- treatment of tularemia due to francisella infection
- treatment of cholera gravis due to vibrio infection
- treatment of the ** bubonic plague due to yersinia infection**
- treatment of tuberculosis due to mycobacterium infection (if resistant to first-choice antituberculotic drugs)
Side effects of streptomycin
- vertigo (due to vestibular nerve damage)
- deafness (due to cochlear nerve damage)
- nephrotoxicity
active against Enterobacter, Indole-positive Proteus, Pseudomonas, Klebsiella, and Serratia spp., among other gram-negative organisms
These agents are often used synergistically in combination with β- lactam antibiotics or vancomycin for serious infections that require broad coverage.
GENTAMICIN and TOBRAMYCIN
Used in the treatment of severe gram-negative infections, especially to those resistant to gentamicin or tobramycin
AMIKACIN
administered topically for minor soft-tissue infections (often in combination with bacitracin and polymyxin) or orally (neomycin) for hepatic encephalopathy (GI bacteria by-products result in large amounts of ammonia, which is normally cleared by the liver; use of ____ temporarily inactivates the normal flora).
NEOMYCIN and KANAMYCIN
_____ neomycin
structurally related to aminoglycosides and is administered intramuscularly as an alternative for treating acute gonorrhea or in patients hypersensitive to penicillin or for gonococci resistant to penicillin.
SPECTINOMYCIN
ADVERSE EFFECTS of aminoglycosides
ototoxicity, nephrotoxicity, and neuromuscular toxicity
The margin of safety with these drugs is small. This means that the toxic concentration is slightly higher than the therapeutic concentration.
The symptoms of ototoxicity include:
The ototoxicity can be both cochlear (auditory) and vestibular.
tinnitus (ringing), deafness, vertigo or unsteadiness of gait, and high-frequency hearing loss.
The cochlear toxicity results from
the selective destruction of the outer hair cells in the organ of Corti
drugs with Vestibular toxicity
drugs with cochlear auditory toxicity
- Vestibular (streptomycin, gentamycin, and tobramycin)
- Cochlear auditory (neomycin, kanamycin, amikacin, gentamicin, and tobramycin )
____ , ____, ____ are nephrotoxic; they produce acute tubular necrosis that leads to a reduction in the glomerular filtration rate and a rise in serum creatinine and blood urea nitrogen. Damage is usually reversible
Gentamicin, neomycin, and tobramycin
At high doses, these agents produce a curare-like neuromuscular blockade with respiratory paralysis
aminoglycosides
antidote for curare-like neuromuscular blockade of aminoglycosides
- Calcium gluconate and
- neostigmine
Aminoglycosides rarely cause hypersensitivity reactions, except ____ and ____ , which, when applied topically, can cause contact dermatitis in as many as 8% of patients.
spectinomycin
neomycin
drugs under TETRACYCLINES
Tetracycline
Oxytetracycline
Demeclocycline
Doxycycline
Minocycline
Tigecycline
binds reversibly to the 30S subunit of bacterial ribosomes. This prevents the binding of aminoacyl tRNA to the acceptor site on the mRNA- ribosome complex and the addition of amino acid to the growing peptide, thus inhibiting bacterial protein synthesis; these agents are bacteriostatic.
Tetracycline
mechanism in which tetracycline is a bacteriostatic
Inhibition of protein synthesis would normally lead to the death of the bacteria, but due to the inhibition occurring after assembly of the ribosome-mRNA complexes, some bacterial proteins are still being randomly translated; thus, tetracyclines are bacteriostatic
how can resistance develops in tetracyclines?
Resistance is plasmid- mediated and results primarily from a decreased activity to accumulate in the bacteria and from the production of an inhibitor of the binding site for tetracyclines.
Resistance to one tetracycline confers resistance to some, but not all congeners.
tetracycline absorption is impaired by
Absorption is impaired by stomach contents, especially milk and antacids.
Tetracyclines are distributed throughout body fluids; therapeutic concentrations in the brain and CSF can be achieved with .____
minocycline
The primary route of elimination for most tetracyclines is the kidney. ____ and ____ do not accumulate and hence are the safest tetracyclines to administer to individuals with impaired renal function
Doxycycline and Tigecycline
Medical Uses of tetracycline
Treatment of
* Rickettsial infection
* Vibrio cholera
* Chlamydia
* Helicobacter pylori
* Mycoplasma pneumoniae
* Plasmodium
* Inflammatory acne vulgaris
* Treatment of syphilis due to treponema infection
* Tigercycine has a broad spectrum of activity and has activity against many tetracycline-resistant organisms
used in refractory cases of SIADH because it interferes with the action of ADH at the renal collecting duct by impairing the generation and action of cyclic AMP
Demeclocycline
side effects of tetracycline
- phototoxicity
- pseudotumor cerebri (benign intracranial hypertension)
- diarrhea (due to gastrointestinal overgrowth by tetracycline-resistant bacteria)
- gastric pain (due to irritation of the gastric mucosa)
-
discoloration and hypoplasia of teeth (due to deposition in teeth, primarily occurs in children)
can complex with calcium resulting to deposition in bone and bone deformities (primarily occurs in children) - hepatic failure and death (if pregnant)
- enters the bacterial cytoplasm through permeases of the inner cell membrane, where it binds to the 50S subunit of assembled ribosome-mRNA complexes
- Here it blocks the conjugation of the previously coded aminoacyl-tRNA with the presently coded aminoacyl-tRNA, thus leading to the inhibition of protein synthesis
CHLORAMPHENICOL
Administered orally and/or IV
May cross the blood-brain barrier
Inhibits cytochrome-450 isozymes (CYP)
chloramphenicol
medical uses of chloramphenicol
- Active against most gram-negative organisms, many anaerobes, Clostridia, Chlamydia, Mycoplasma, and Rickettsia
- Treatment of meningitis due to Haemophilus infection
- Treatment of typhoid fever due to Salmonella infection
Side effects of CHLORAMPHENICOL
- Hypersensitivity reactions leading to fever, skin rashes, and/or angioedema
- Diarrhea (due to gastrointestinal overgrowth by chloramphenicol-resistant bacteria)
- Bone marrow depression leading to pancytopenia and death
- Hemolytic anemia (if glucose-6phosphate dehydrogenase deficiency)
- Gray baby syndrome
- Due to the inadequacy of both cytochrome-450 glucuronic conjugation systems to detoxify the drug
- Due to the inhibition of mitochondrial protein synthesis and following decreased aerobe glycolysis in neonates
This can result in elevated and toxic levels of other drugs metabolized by CYP
DRUGS UNDER MACROLIDES
- Erythromycin
- Clarithromycin
- Azithromycin
- Telithromycin
enter the bacterial cytoplasm through permeases of the inner cell membrane, where they bind to the 50S subunit of assembled ribosome-mRNA complexes
Macrolides
block the translocation of the ribosome along the mRNA to the next codon, thus leading to the inhibition of protein synthesis
Macrolides
Inhibition of protein synthesis would normally lead to the death of the bacteria, but due to the inhibition occurring after assembly of the ribosome-mRNA complexes, some bacterial proteins are still being randomly synthesized; thus macrolides are bacteriostatic (but maybe bactericidal in some bacteria, and in high doses)
true or false
true
resistance for macrolides
Resistance is plasmid-encoded and is prevalent in most strains of staphylococci and, to some extent, in streptococci. due primarily to increased active efflux or ribosomal protection by increased methylase production
- is inactivated by stomach acid and is therefore administered as an enteric-coated tablet.
- distributes into all body fluids except the brain and CSF
Erythromycin
Therapeutic uses of erythromycin
- Erythromycin is active against gram-positive organisms.
- Useful as a penicillin substitute in penicillin-hypersensitive patients.
- Most effective drug for Legionnaires disease (Legionella pneumophila); it is also useful for the treatment of syphilis, M. pneumoniae, corynebacterial infections (e.g., diphtheria), and Bordetella pertussis disease (whooping cough).
commonly used for community-acquired “walking” pneumonia and sinusitis.
Azithromycin
is effective in the multidrug-regimen treatment of disseminated Mycobacterium avium–intracellulare complex infections in AIDS patients.
Clarithromycin or azithromycin
Adverse effects of macrolides
- Erythromycin and other macrolides cause GI dysfunction (clarithromycin less so) but rarely produce serious adverse effects; the oral form of erythromycin may cause allergic cholestatic hepatitis, which is readily reversible by cessation of the drug.
- Erythromycin has a high incidence of thrombophlebitis when administered IV.
- Erythromycin and clarithromycin inhibit hepatic cytochrome P-450–mediated metabolism of warfarin, phenytoin, and others, possibly leading to toxic accumulation.
- Azithromycin is devoid of this action.