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OPHTHALMOLOGY > OCULAR DRUGS (Ocular routes & Antibacterial) > Flashcards

OCULAR DRUGS (Ocular routes & Antibacterial) Flashcards

1
Q

What is the absorption pattern of topical (eye drops or ointment) administration?

A

Through the conjunctiva, the absorption is rapid/prompt, depending on formulation.

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2
Q

What are the special utilities of topical administration (eye drops or ointment)?

A

Convenient, economical, relatively safe.

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3
Q

What are the limitations and precautions of topical administration (eye drops or ointment)?

A

Compliance, corneal and conjunctival toxicity, nasal mucosal toxicity, systemic side effects from nasolacrimal absorption. The patient should close the eye for at least 5 minutes after instilling the eyedrops to prevent systemic absorption.

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4
Q

What is the pathway of eyedrops after instillation?

A

The eyedrops pass through the canaliculus, nasolacrimal sac, nasolacrimal duct, the nose, and then are swallowed. They are very concentrated drugs that can cause systemic side effects when absorbed.

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5
Q

What is the absorption pattern of subconjunctival, Sub-Tenon’s, or retrobulbar injections?

A

Prompt or sustained, depending on formulation.

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6
Q

What are the special utilities of subconjunctival, Sub-Tenon’s, or retrobulbar injections?

A

Anterior segment infections, posterior uveitis, cystoid macular edema.

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7
Q

What are the limitations and precautions of subconjunctival, Sub-Tenon’s, or retrobulbar injections?

A

Local toxicity, tissue injury, globe perforation, optic nerve trauma, central retinal artery and/or vein occlusion, direct retinal drug toxicity with inadvertent globe perforation, ocular muscle trauma, prolonged drug effect.

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8
Q

What is intracameral administration?

A

Injection of the drug into the anterior chamber of the eye.

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9
Q

What is the absorption pattern of intracameral injections?

A

Prompt.

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10
Q

What are the special utilities of intracameral injections?

A

Anterior segment surgery, infections.

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11
Q

What are the limitations and precautions of intracameral injections?

A

Corneal toxicity, intraocular toxicity, relatively short duration of action. Toxicity is the primary limitation.

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12
Q

What is the absorption pattern of intravitreal injection or device administration?

A

Absorption is circumvented; it has an immediate or local effect, with potential for a sustained effect.

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13
Q

What are the special utilities of intravitreal injection or device administration?

A

The drug is administered directly to the site of action. Used for endophthalmitis, retinitis, and age-related macular degeneration.

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14
Q

What are the limitations and precautions of intravitreal injection or device administration?

A

Renal toxicity, degenerations in the macula.

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15
Q

What is the absorption pattern of Azithromycin?

A

Topical 1% solution or oral (PO) with enteric-coated tablets or acid-resistant salts since it is inactivated by acid.

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16
Q

How is Azithromycin distributed in the body?

A

Distributes to most body compartments, only crossing inflamed meninges.

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17
Q

What is the half-life (t1/2) of Azithromycin?

A

68 hours.

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18
Q

How is Azithromycin excreted?

A

Released into bile and feces as an active drug, making it effective for biliary infections.

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19
Q

What is the mechanism of action of Azithromycin?

A

Bacteriostatic; reversibly binds to the 50S ribosomal subunit and blocks protein synthesis.

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20
Q

What is the resistance mechanism against Azithromycin?

A

Resistance develops mostly from mutations in the binding site on the 50S ribosomal subunit.

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21
Q

What is the spectrum of activity and clinical uses of Azithromycin?

A

Same as erythromycin plus H. influenzae, Moraxella, and Chlamydia. Used for community-acquired pneumonia, pertussis, Corynebacterium infections, and conjunctivitis.

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22
Q

What is unique about Azithromycin’s pharmacokinetics in infections?

A

Taken up by phagocytes and transported to the site of infection, allowing for 24-hour dosing in a 5-day cycle.

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23
Q

What are the drawbacks and side effects of Azithromycin?

A

GI upset, abdominal cramping, gas, diarrhea, rare intestinal superinfections, cholestatic hepatitis with estolate salts, QT elongation, and hypersensitivity reactions.

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24
Q

Does Azithromycin inhibit cytochrome P450 enzymes?

A

No, it does not inhibit cytochrome P450 enzymes, but it interacts with the cytochrome P450 system, potentially causing drug interactions (e.g., with theophylline and carbamazepine).

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25
Q

What is the most significant side effect of Azithromycin when used topically?

A

Hypersensitivity reactions.

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26
Q

What is the absorption pattern of Bacitracin?

A

Administered topically as a 500 units/g ointment. A small absorbed amount is excreted in urine.

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27
Q

What is the mechanism of action of Bacitracin?

A

Produced by Tracy-I of Bacillus subtilis; interferes with the late stage of bacterial cell wall synthesis.

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28
Q

What is the spectrum of activity of Bacitracin?

A

Active against G+ cocci and bacilli, Neisseria, H. influenza, Treponema pallidum, Actinomyces, and Fusobacterium.

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29
Q

What are the clinical uses of Bacitracin?

A

Used for suppression of flora in surface abrasions or wounds, conjunctivitis, blepharitis, keratitis, keratoconjunctivitis, corneal ulcers, blepharoconjunctivitis, meibomianitis, and dacryocystitis.

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30
Q

What are the drawbacks and side effects of Bacitracin?

A

Nephrotoxic (only used topically) and hypersensitivity reactions.

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31
Q

What are the routes of administration for Chloramphenicol?

A

Topical 1% ointment or drops, PO (well-absorbed), IV, IM.

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32
Q

What is the oral availability of Chloramphenicol?

A

0.8

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33
Q

What is the half-life (t1/2) of Chloramphenicol?

A

2.5 hours.

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34
Q

What is the volume of distribution (Vd) of Chloramphenicol?

A

66 L/70 kg.

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35
Q

What is the mechanism of action of Chloramphenicol?

A

Bacteriostatic; bactericidal for H. influenzae. Binds reversibly to a receptor and inhibits activity of bacterial 50S ribosomal subunit.

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36
Q

What is the resistance mechanism for Chloramphenicol?

A

Resistance occurs via enzymatic inactivation, but this does not happen in Rickettsia species.

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37
Q

What are the clinical uses of Chloramphenicol?

A

Broad spectrum for G+ and G-. First choice for H. influenzae in children, conjunctivitis, and keratitis.

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38
Q

What are the major drawbacks and side effects of Chloramphenicol?

A

Bone marrow suppression (reversible/irreversible), gray baby syndrome, dose-related anemia, hypersensitivity, and toxicity to neonates.

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39
Q

What is a way to prevent systemic absorption of Chloramphenicol during topical use?

A

Press on the lacrimal sac for at least 5 minutes.

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40
Q

What is the absorption pattern of Erythromycin?

A

Topical 0.5% ointment, PO (requires enteric-coated tablets or acid-resistant salts), IV.

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41
Q

What is the oral availability of Erythromycin?

A

0.35

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42
Q

What is the mechanism of action of Erythromycin?

A

Bacteriostatic; reversibly binds to the 50S ribosomal subunit and blocks protein synthesis.

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43
Q

What are the resistance mechanisms for Erythromycin?

A

Mutations in the 50S ribosomal subunit binding site.

44
Q

What is the spectrum of activity of Erythromycin?

A

G+ organisms, Mycoplasma pneumoniae, Chlamydia (safe for pregnant women), Legionella pneumoniae, Campylobacter jejuni.

45
Q

What are the clinical uses of Erythromycin?

A

Community-acquired pneumonia, pertussis, superficial ocular infections, and prophylaxis of ophthalmia neonatorum.

46
Q

What are the side effects of Erythromycin?

A

GI upset, abdominal cramping, QT elongation, hepatotoxicity, CYP450 inhibition, and hypersensitivity.

47
Q

What is the mechanism of action of Gentamicin Sulfate?

A

Inhibits bacterial protein synthesis by binding to 30S ribosomes; bactericidal.

48
Q

What is the spectrum of activity of Gentamicin?

A

Broad spectrum, except for streptococci and anaerobic bacteria.

49
Q

What are the clinical uses of Gentamicin?

A

Conjunctivitis, keratitis, corneal ulcers, dacryocystitis, and superficial infections.

50
Q

What are the drawbacks of Gentamicin?

A

Hypersensitivity and toxicity concerns.

51
Q

What is the absorption pattern of Tobramycin?

A

Topical 0.3% solution or ointment, IM, and IV (good absorption).

52
Q

What is the mechanism of action of Tobramycin?

A

Bactericidal; binds to the 30S ribosomal subunit, causing abnormal peptide synthesis. Synergistic with β-lactams.

53
Q

What is the spectrum of activity of Tobramycin?

A

Aerobic G- rods, H. influenzae, M. catarrhalis, Shigella species, and limited activity against facultative anaerobes.

54
Q

What are the clinical uses of Tobramycin?

A

External infections of the eye, adnexa, and superficial infections.

55
Q

What are the drawbacks and side effects of Tobramycin?

A

Nephrotoxicity (reversible), ototoxicity (irreversible), neuromuscular blockade (rare), and hypersensitivity.

56
Q

What is the mechanism of action of Sulfacetamide Sodium?

A

Blocks the synthesis of dihydrofolic acid by inhibiting the enzyme dihydropteroate synthase; inhibits DNA synthesis by preventing tetrahydrofolic acid formation.

57
Q

What are the indications for Sulfacetamide Sodium?

A

Conjunctivitis and other superficial ocular infections.

58
Q

What are the adverse effects of Sulfacetamide Sodium?

A

Hypersensitivity and blood dyscrasias.

59
Q

What is the spectrum of activity of Sulfacetamide Sodium?

A

Effective against gram-positive and gram-negative bacteria.

60
Q

What is the mechanism of action of Polymyxin B?

A

Alters the cytoplasmic membrane causing cellular leakage, disrupts bacterial cell membrane structure, and binds to the lipid A portion of endotoxin, inactivating it.

61
Q

What are the indications for Polymyxin B?

A

Conjunctivitis, blepharitis, keratitis, and superficial infections.

62
Q

What are the adverse effects of Polymyxin B?

A

Nephrotoxicity and hypersensitivity.

63
Q

What bacteria are targeted by Polymyxin B?

A

Gram-negative bacteria including Enterobacter, E. coli, Klebsiella, Salmonella, Pseudomonas aeruginosa, and others.

64
Q

What is the mechanism of action of Besifloxacin?

A

Inhibits DNA gyrase (in gram-negative bacteria) and topoisomerase IV (in gram-positive bacteria), preventing DNA unwinding required for replication.

65
Q

What are the key adverse effects of Besifloxacin?

A

Nausea, diarrhea, skin rashes, QTc prolongation, and risk of tendinitis or tendon rupture.

66
Q

Why is Besifloxacin contraindicated in patients under 18 years old?

A

Due to the possibility of damage to growing cartilage.

67
Q

What infections can Besifloxacin treat?

A

UTIs, lower respiratory tract infections, conjunctivitis, keratitis, bone/joint infections, sinusitis, and more.

68
Q

What are the drug interactions of Besifloxacin?

A

Enhances warfarin effects, prolongs theophylline elimination, and increases CNS stimulation risk with NSAIDs.

69
Q

What is the mechanism of action of Ciprofloxacin?

A

Inhibits DNA gyrase and topoisomerase IV, preventing DNA replication and transcription.

70
Q

What is the oral bioavailability of Ciprofloxacin?

A

0.7

71
Q

What are the common indications for Ciprofloxacin?

A

Conjunctivitis, keratitis, respiratory tract infections, UTIs, and GI tract infections.

72
Q

What are the adverse effects of Ciprofloxacin?

A

Nausea, diarrhea, QTc prolongation, CNS effects, and tendon rupture risk.

73
Q

How is Ciprofloxacin eliminated from the body?

A

Through tubular secretion or glomerular filtration, with 65% urinary excretion.

74
Q

What is the mechanism of action of Ofloxacin?

A

Inhibits DNA gyrase and topoisomerase IV, disrupting DNA replication and transcription.

75
Q

What is the oral bioavailability of Ofloxacin?

A

0.95

76
Q

What are the common indications for Ofloxacin?

A

Conjunctivitis, keratitis, sinusitis, chronic bronchitis, UTIs, and GI tract infections.

77
Q

What are the key adverse effects of Ofloxacin?

A

QTc prolongation, nausea, diarrhea, tendon rupture risk, and hypersensitivity.

78
Q

Why should Ofloxacin be avoided in young children and pregnant patients?

A

Due to the risk of tendon rupture and cartilage damage.

79
Q

What drug interactions are associated with Ofloxacin?

A

Enhanced warfarin effects, prolonged theophylline elimination, and blood glucose disturbances with antidiabetics.

80
Q

What are the administration routes for Levofloxacin?

A

Topical 0.5% and 1.5% solution, IV, IM, SC, intrathecal, intraperitoneal

81
Q

What is the bioavailability of Levofloxacin?

A

24-38%

82
Q

What is the peak serum concentration of Levofloxacin?

A

5.7 mcg/mL

83
Q

What is the distribution volume (D) of Levofloxacin?

A

89-112 L, rapid and extensive skin tissue and blister fluid penetration, penetrates well into lung tissue

84
Q

How is Levofloxacin excreted?

A

In the urine through tubular secretion and glomerular filtration

85
Q

What is the mechanism of action of Levofloxacin?

A

Bactericidal; prevents DNA unwinding required for transcription and translation by inhibiting DNA gyrase and topoisomerase IV

86
Q

What mechanisms lead to resistance to Levofloxacin?

A

Alteration of membrane permeability into the bacterial cell and microbial modification of DNA gyrase structure

87
Q

What aerobic gram-positive organisms is Levofloxacin effective against?

A

Enterococcus faecalis, Methicillin-susceptible S. aureus, Methicillin-resistant S. epidermidis, S. saprophyticus, S. pneumoniae, S. pyogenes

88
Q

What aerobic gram-negative organisms is Levofloxacin effective against?

A

Enterobacter cloacae, E. coli, H. influenzae, H. parainfluenzae, K. pneumoniae, Legionella pneumophila, M. catarrhalis, P. mirabilis, P. aeruginosa, Serratia marcescens

89
Q

What are common adverse effects of Levofloxacin?

A

Nausea, diarrhea, skin rashes, abnormal LFTs, CNS effects like headache, dizziness, and tremor, QTc prolongation, risk of tendinitis and tendon rupture

90
Q

What are important drug interactions with Levofloxacin?

A

Prolonged elimination half-life and elevated serum theophylline levels, enhanced effects of warfarin, NSAIDs may increase CNS stimulation and convulsive seizures, disturbance of blood glucose with antidiabetic agents

91
Q

What are the administration routes for Moxifloxacin?

A

Topical 0.5% solution, PO, IV

92
Q

What is the oral bioavailability of Moxifloxacin?

A

> 85%

93
Q

What is the peak serum concentration of Moxifloxacin?

A

3.1 mcg/mL

94
Q

What is the half-life (t1/2) of Moxifloxacin?

A

9-10 hours

95
Q

How is Moxifloxacin metabolized?

A

Hepatically

96
Q

What is the mechanism of action of Moxifloxacin?

A

Bactericidal; interferes with topoisomerases II and IV, inhibiting DNA replication, repair, and transcription

97
Q

What organisms is Moxifloxacin effective against?

A

Similar spectrum as Levofloxacin, including gram-positive cocci, gram-negative bacilli, and atypicals

98
Q

What are the contraindications for using Moxifloxacin?

A

Patients younger than 18 years, pregnancy due to risk of cartilage damage

99
Q

What are common adverse effects of Moxifloxacin?

A

Nausea, diarrhea, skin rashes, abnormal LFTs, CNS effects, QTc prolongation

100
Q

What are important drug interactions with Moxifloxacin?

A

Similar to Levofloxacin: prolonged elimination half-life, enhanced effects of warfarin, risk of CNS stimulation with NSAIDs

101
Q

What is the administration route for Gatifloxacin?

A

Topical 0.3% solution, PO

102
Q

What is the oral bioavailability of Gatifloxacin?

A

0.95

103
Q

What is the peak serum concentration of Gatifloxacin?

A

3.4 mcg/mL

104
Q

What is the half-life (t1/2) of Gatifloxacin?

A

8 hours

105
Q

How is Gatifloxacin excreted?

A

Renally

106
Q

What is the mechanism of action of Gatifloxacin?

A

Bactericidal; prevents DNA unwinding required for transcription and translation by inhibiting DNA gyrase and topoisomerase IV

OPHTHALMOLOGY (4 decks)

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