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Pharmacology > *Anti-infectives > Flashcards

*Anti-infectives Flashcards

1
Q

Define antibiotics

A 
* An antibiotic is a chemical substance originating from various species
 of microorganisms (bacteria, fungus, actinomyces) that suppresses
 growth or destroys other microorganisms
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2
Q

Activity Spectrum of Gram + and -

A
  • Gram+ & Gram-
    • Secrete unique antigenic non-enzymatic heat sensitive protein
      exotoxins
  • Gram-
    • Release pyretic, heat stable, mildly antigenic endotoxin (LPS) upon lysis

Metabolic Profiles

  • Aerobic
  • Anaerobic (facultative vs obligate): commonly indigenous flora thriving in a poorly perfused environment
  • Obligate intracellular species
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3
Q

Bactericidal vs bacteriostatic

A
  • Bactericidal: kill target cells; cells may lyse or remain intact
  • Bacteriostatic: prevent target cell replication
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4
Q

THERAPEUTIC CONCERNS

A
  • Route Of Delivery
    • Highest ocular concentrations are delivered locally (topical, contact lens, injection etc.)
  • Dose
    • Dependent on weight, height, organ function
  • Duration Of Therapy
    • Longer isn’t always better; see resistance
  • Drug Safety
  • Liquid antibiotics are among the few drug formulations that
    are not recommended for use after expiration dates*
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5
Q

Antibiotic cover at a glance

A
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6
Q

Antibiotic cover

A
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7
Q

ANTIBIOTIC TOXICITY PROFILE

(bactericidal vs bacteriostatic)

A
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8
Q

Cell wall inhibitors

A
  • β-Lactam Antibiotics
    • • Penicillin [PCN]
    • Cephalosporin
  • Stand-alone Antibiotics (no structural relatives)
    • Bacitracin
    • Vancomycin

The cell wall and inner peptidoglycan layer found in bacteria are not
found in humans thus make great targets for antibiotic therapy

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9
Q

Penicillin

A
  • Predominantly useful for treating Gm+ infections & anaerobic infections Drug of choice for syphilis
  • PCNase Sensitive
    • Pen G (IV, IM) & Pen V (PO); the original (non-synthetic) penicillins
  • PCNase Resistant
    • Methicillin, Flucloxacillin, Dicloxacillin
  • *Aminopenicillins
    • Ampicillin, Amoxicillin
  • Anti-pseudomonal (Gm-) Coverage
    • Carboxypenicillins: Carbenicillin and Ticarcillin

*Sulbactam or Clavulanate inhibit PCNase and are therefore
Often combined with PCNase sensitive formulas

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10
Q

Penicillin

A
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11
Q

Adverse reactions of Penicillin

A
  • No topical formulas exist since allergy risk is too high
    • Hypersensitivity

• Penicillin haptens bind to RBC surface proteins which then become
immunogenic and stimulate IgE (Type I: anaphylaxis) and/or IgG
(Type II: hemolysis) reactions

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12
Q

Cefalosporins

A
  • Like PCN, these drugs also have a β-lactam ring structure
    with 6 members (vs 5)
  • In contrast to PCN, these drugs are less susceptible to
    PCNase

The first 3 of 4 Generations include oral formulations
• No topical formulas exist
• Newer generations have greater Gram- coverage

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13
Q

Adverse reactions of cephalosporins

A
  • Hypersensitivity reactions similar to penicillin
  • 1st generation cephalosporins are cross-reactive with
    penicillins
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14
Q

BACITRACIN

A
  • Available in a topical ointment ONLY due to profound nephrotoxicity
  • AK-Tracin® Ointment
    • ​Gm+ coverage
  • Polysporin® Ointment
    • Also contains Polymyxin B
      • The combination provides additional Gm- coverage including pseudomonas
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15
Q

VANCOMYCIN

A
  • I.V. drug of choice for MRSA and MRSE infections and
    bacterial endophthalmitis
  • Gm+ coverage only
  • Poor oral absorption
  • Adverse Reactions
    • Red Man Syndrome: IV-induced mast cell degranulation
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16
Q

CELL MEMBRANE TOXINS

Polymyxin-B

Gramicidin

A

Only available topically due to systemic toxicity

Polymyxin-B
• Cationic detergent/surfactant
• Topical use only; never stand-alone

Gramicidin
• Same mechanism of action as Polymyxin B
• Often found in combination products

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17
Q

POLYMYXIN-B OPH COMBOS

A

Polytrim Solution
• Polymyxin-B + Trimethoprim used for most common
paediatric ocular infections: H influenzae and S pneumoniae
• Excellent option for resistant S epidermidis & MRSA
infections

Polysporin Ointment
• Polymyxin B + Bacitracin

Neosporin Ointment
• Polymyxin B + Neomycin + Bacitracin

Neosporin Solution
• Polymyxin B + Neomycin + Gramicidin

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18
Q

PROTEIN SYNTHESIS INHIBITORS

A

Act by binding to and inhibiting the 30S or 50S ribosomal
subunit

30S
• Aminoglycosides
• Tetracyclines

50S
• Macrolides
• Lincosamides (Lincomycin, Clindamycin)
• Chloramphenicol

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19
Q

AMINOGLYCOSIDES

A

Neomycin (Neosporin® Combo Ointment/Solution)
• The oldest aminoglycoside
• Topical use primarily; never stand-alone
• Broad spectrum coverage except pseudomonas

Gentamicin (Garamycin® Ointment/Solution)
• Used for severe infections

Tobramycin (Tobrex® Ointment/Solution)
• Similar use as Gentamicin

20
Q

Adverse reactions of aminoglycosides

(Neomycin,gentamycin,tobramycin)

A
  • Adverse Reactions
    • Type IV Delayed Hypersensitivity reaction

Neomycin
• 5-10% contact dermatitis risk: avoid routine use
• Allergy: 50% patients are X-reactive w/ Gentamicin

Gentamicin
• Idiopathic Intracranial Hypertension
• Corneal epithelial toxicity most pronounced

21
Q

TETRACYCLINES

A

Anti-inflammatory benefits arise through inhibition of
MMPs, neovascularization & bacterial lipases

Short Acting
• Tetracycline, Oxytetracycline

Long Acting
• Doxycycline, Minocycline
• Oracea® is a 40 mg doxycycline capsule; 30 mg is
immediately released; 10 mg is delayed release; indicated
for rosacea

22
Q

Indications of tetracyclines (minocycline,doxacycline)

A
  • Minocycline
    • Acne rosacea
  • Doxycycline (50mg qd x 1-6 months)
    • Acne rosacea
    • Chlamydia
    • Syphilis (vs 1st choice intramuscular PCN)
23
Q

Adverse reactions of tetracyclines (minocycline and doxycycline)

A

General adverse reactions

  • Photosensitivity
  • Impaired absorption w/ food due to divalent cation binding;
    doxycycline ⇩ 20% vs tetracycline ⇩ 50% w/ milk; avoid lying
    down for 2 hrs following administration
  • Blood dyscrasias
  • “Idiopathic” Intracranial Hypertension [IIH]
  • Impaired bone growth, tooth development
  • Fanconi’s Syndrome: renal toxicity from expired tetracyclines

Distinct adverse reactions

  • Minocycline
    • Vestibular toxicity within 2-3d of therapy in up to 70%
  • Doxycycline (Vibramycin®)
    • Exhibits least divalent chelation (20% w/ milk)
    • Risk of erosive esophagitis*
    • No azotemia due to fecal (vs renal) elimination pathway
    • Excellent option for resistant S epidermidis infection (MRSE)
24
Q

Contraindications for the use of tetracyclines (doxycycline,minocycline)

A
  • Pregnancy
  • Nursing mothers
  • Children under 8 yrs of age
  • Renal failure (except Doxycycline)
25
Q

MACROLIDES

A

Erythromycin QID (Ilotycin® Ointment)
• Replaced AgNO3 for neonatal gonorrhea
• Unstable in gastric acid

Azithromycin (Oral & AzaSite® Solution w/ *Durasite®)
• The ONLY macrolide available in a drop formulation
• Extended half-life* permits minimal dosing

Clarithromycin BID (Biaxin® oral)
• Reduced dosing compared to Erythromycin due to greater
stability in GIT

E-Mycin and Azasite are two of very few antibiotics that have a safer pregnancy rating

26
Q

Adverse reactions and cautions for the use of macrolides (erythromycin,azithromycin,clarithromycin)

A

Adverse Reactions
• None applicable to ophthalmic conditions or findings

Contraindications
• Pregnancy

27
Q

CHLORAMPHENICOL

A

Adverse Effects
• Grey Baby Syndrome
Ocular
• Optic neuritis with prolonged therapy

• High oral toxicity limits use to topical only in USA
• Grey Baby Syndrome: results from IV use in newborns with immature
liver function- unmetabolized drug causes reduced blood pressure and
cyanosis (grey color) results

28
Q

P37

A
29
Q

FOLIC ACID INHIBITOR COMBOS

A

Polytrim Solution
• Polymyxin B + Trimethoprim is the drug of choice for
paediatric bacterial conjunctivitis

Sulfadiazine + Pyrimethamine
• These two drugs are used together to treat toxoplasmosis

Sulfamethoxaxole + Trimethoprim (Bactrim®)
• Oral drug of choice for MRSA

30
Q

Adverse reactions and contraindications of folic acid inhibitors (Sulfamethoxazole, Sulfacetamide, Sulfadiazine,Pyrimethamine, Trimethoprim)

A

Adverse Reactions

• Hypersensitivity
Ocular: (Sulfonamides)

• Myopia +/- astigmatism (reversible)

Contraindication
• Pregnancy

31
Q

DNA SYNTHESIS INHIBITORS (fluoroquinolones)

A
  • The most commonly used class of antibiotics
  • Newer generations provide greater gm + coverage over and
    above the excellent gm - coverage
  • Nalidixic acid is the original, 1st gen fluoroquinolone; not used in
    eyecare
  • Ciprofloxacin is available as an ointment also; the solution has no
    age restrictions

Bactericidal; inhibit DNA gyrase and topoisomerase IV

  • 1st Generation
    • Nalidixic acid
  • 2nd Generation
    • Norfloxacin, Ciprofloxacin, Ofloxacin
  • 3rd Generation
    • Gemifloxacin, Levofloxacin
  • 4th Generation [2003] (“Respiratory Quinolones”)
    • Moxifloxacin, Delafloxacin
32
Q

Fluoroquinolone adverse reactions and contraindications (Ciprofloxacin,ofloxasin,moxiflox)

A

Adverse Reactions
• CNS disturbances: insomnia, confusion, impaired memory, delirium…

Contraindications
• MG
• QT prolongation, arrhythmias, cardiopathies
Black Box Warnings
• Tendonitis, tendon rupture
• Peripheral neuropathy, CNS effects
• Avoid in myasthenia gravis (exacerbation of muscle weakness)

33
Q

CHEMOTHERAPEUTIC ANTIBIOTICS (Mitomycin)

A

*

34
Q

Adverse effects of topical mitomycin (chemotherapeutic antibiotic)

A

Adverse Reactions
• Ocular: Blebitis, corneal reaction, endophthalmitis, hypotony,
iritis

Severe:
• Ocular: Cataracts, retinal detachment, vision loss

35
Q

ANTIBIOTIC RESISTANCE

A
  • 80% of the 35 million lbs of ABX used annually in the US is for animal growth promotion
  • In 2019, antibiotic resistance was responsible for the death of 40,000 Americans
  • Resistance is notably problematic with fluoroquinolones and macrolide antibiotics
  • Only ABX have transmissible resistance; Gm⊖ are especially adept at exchanging DNA within their phyla
  • Antibiotic treatment regimens are routeinely exaggerated in length; many studies have shown that shorter intervals (3-7 days) are as effective as longer intervals (7-15 days)
  • 1 to 2-week regimens date back almost 1700 years when Roman Emperor Constantine the Great ruled that there would be 7 days in a week
  • Drug companies are motivated to create drugs intended for long term or chronic use; new ABX are increasingly uncommon
36
Q

ANTIBIOTIC RESISTANT BACTERIA

A

ESKAPE Bacteria

Gm ⊕

  • Enterococcus (VRE)
  • Staph. Aureus (MRSA)

Gm ⊖

  • Klebsiella
  • Acinetobacter
  • Pseudomonas
  • ESBL (e.g. E. coli, Enterobacter)

ESBL: extended spectrum beta-lactamase producing bacteria

  • Rational use of antibiotics is essential to reduce the ongoing development of antimicrobial resistance
  • Select drugs with the narrowest spectrum necessary for the causative organism
  • Use older agents whenever possible; use later generations or fortified formulations for more serious infections

New Paradigms

  • Treatment to enhance immunity or disarm pathogens, reducing virulence without cidal actions
  • Modulate the host inflammatory response
  • Chelate metals etc. that microbes need to thrive
  • Use probiotics to crowd-out pathogens
  • There is no data to support the claim that a full treatment course must be completed after symptoms are gone; encourage patients to call once symptoms resolve
37
Q

Antivirals

A
  • In contrast to viricides and many antibiotics, antiviral agents are designed to inhibit viral replication or proliferation
  • Because viruses replicate only upon entering cells, they are “hidden” and “protected” within cells
  • Cells that host viral particles may experience collateral damage when
    antiviral agents are used
  • Viral mutation affects antiviral drug therapy efficacy; like antibiotics,
    antiviral resistance is a common concern
  • DNA viruses, which are much more abundant that RNA viruses, live with us for a lifetime
  • RNA viruses have simple structures, mutate rapidly, and are responsible for many historic epidemics: measles, Ebola, Zika, influenza, and Corona virus
38
Q

Common ocular viruses

A
  • Adenovirus is a cold virus that is the most common cause of
    eye infection
    • It results in a highly infectious conjunctivitis and/or keratitis
      commonly called pinkeye
    • There is currently no FDA-approved treatment for ocular
      adenovirus infections which are normally self-resolving
    • Palliative care and proper hygiene precautions are advised
  • Herpes Simplex Virus (HSV) is the most common virus of the human body: like Herpes (Varicella) Zoster Virus (HZV), it resides in the ganglia of nerves for life
  • By the 4th decade of life, approximately 65% of the US population is seropositive for HSV-1 and 25% for HSV-2; women are infected with HSV-2 more often than men
  • Unlike HSV, HZV is responsible for a common childhood infection
    • HZV: Chicken Pox (children); Shingles (adults)
    • HSV: Type I (orofacial & genital); Type II (genital)
  • HZV and HSV can infect both the anterior and posterior segments of the eye
  • Human Immunodeficiency Virus (HIV), a retrovirus, has RNA in its genome but
    behaves like DNA in the host
    • Patients with HIV have an increased risk of 2° infection by cytomegalovirus (CMV)
    with AIDS
39
Q

ANTIVIRAL AGENTS FOR HERPES

A
  • Purines are the two-carbon nitrogen ring bases that are used to produce the DNA/RNA nucleotides adenine and guanine
  • Pyrimidines are the one-carbon nitrogen ring bases that are used to produce the DNA/RNA nucleotides thymine and cytosine
  • Commonly antiviral agents for herpes (simplex and keratitis) are analogs of pyrimidines (topical ophthalmic formulas only) or purines

PURINE ANALOGS

  • Acyclovir (Zovirax®) 200/400/800 mg pO (now in liquid)
    • Poorest GI absorption vs Valacyclovir and Famciclovir
    • Contains gluten
  • Valcyclovir (Valtrex®) 500/1000 mg pO
    • Acyclovir prodrug w/ very long plasma half-life
    • X-sensitivity seen w/ Acyclovir
  • Famciclovir (Famvir®) 125/250/500 mg pO
    • Penciclovir prodrug w/ extended plasma life
40
Q

FUNGAL INFECTIONS

A

70,000 + species of fungi (eukaryotes)
• Budding unicellular yeasts
• Branching filamentous molds

Ocular involvement
• Cornea, conjunctiva, lens, ciliary body, vitreous body, uvea
• Yeasts: Candida, Cryptococcus
• Molds: Aspergillus, Fusarium, Curvularia
• Enhanced risk of infection w/ contact lens wear, steroids, trauma (inc
LASIK), immunocompromise

Therapeutic concerns
• Drug adverse effects, narrow spectrum of drug activity, poor tissue
penetration, drug resistance

41
Q

ANTIFUNGALS

A

Polyenes
• Amphotericin B
• Natamycin (only FDA approved topical; Pregnancy: C)

Pyrimidines
• Flucytosine

Azoles
• Ketoconazole*, Fluconazole, Posaconazole, Voriconazole# ,Itraconazole, Miconazole

Echinocandins
• Caspofungin, Micafungin, Anidulafungin

42
Q

Mechanism of action of polyenes (amphoteracin b, natamycin)

A
  • Bind fungal ergosterol- increased membrane permeability
    (fungistatic low dose/ fungicidal high dose)
43
Q

Mechanism of action of Pyrimidines (Flucytosine) antifungal

A
  • (developing resistance; rarely used alone)
    • Inhibit thymidine synthesis (fungistatic)
44
Q

Mechanism of action of azoles(ketoconazole, clotrimazole,fluconazole,itraconazole)

A
  • (developing resistance)
    • Impair ergosterol synthesis (fungistatic) & some cytochrome
    P450 enzymes: may reduce metabolism of other drugs
45
Q

Mechanism of action of Echinocandins (Caspofungin, Micafungin, Anidulafungin) antifungal

A
  • Inhibit glucan synthesis- weaken cell wall
  • Poor oral availability
46
Q

Adverse reactions relating to topical opthalmics with antifungals

A
  • None applicable to ophthalmic conditions or findings

Pharmacology (19 decks)

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