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Spring OD1- Pharmacology > MT2 Ophthalmic Drug Formulation & Bioavailability > Flashcards

MT2 Ophthalmic Drug Formulation & Bioavailability Flashcards

1
Q

Prodrug - Drug formulation and Bioavailability

A

Prodrug design can be useful way of **increasing penetration of therapeutic agent through corneal or other barriers

  • clopidogrel
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2
Q

Prodrug – through corneal barrier

A

(ester prodrugs) prostaglandins are used to treat high IOP

  • After corneal penetration*, ester-linked molecular group
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3
Q

Prostaglandins (ester prodrugs)

A

Latanoprost (Xalatan)
Travoprost (Travatan)
Tafluprost (zioptan)

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4
Q

Retro-metabolic drug design (Soft Drug Concept)

A

new compound creased based on inactive metabolite of a previous compound

Goal - retain therapeutic efficacy and minimize adverse side effects

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5
Q

Loteprednol (Lotemax)

A

active ester-metabolite
- * designed as soft steroid – to be rapidly hydrolyzed by enzymes
- has short half-life and is associated with a lower incidence of adverse effects than ketone-based steroids (prednisolone)

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6
Q

Active Pharmaceutical Ingredient (API)

A
  • any component of a drug product intended to furnish pharmacological activity
  • components of a drug compound that illicit a pharmacological effect
  • the chemicals in the drug that make the medications work
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7
Q

What are excipients?

A

inactive or inert substances present inside drug compound
- not an active pharmaceutical ingredient

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8
Q

Stability of API

A
  • complex drug molecules will lose stability in SOLUTION form – why there are expiration dates
  • range of API may range depending on therapeutic index (ratio of toxic dose to therapeutic index (ratio of toxic dose to therapeutic dose)
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9
Q

Unstable example: Acetylcholine (Miochol-E)

A

degrades within minutes in solution

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10
Q

Factors that effect stability

A

Oxidation - can break down drugs (ex: proparacaine)

microbial contamination - affects formulas

heat - accelerates breakdown

pH* - drugs in acid medium can be more stable

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11
Q

Osmolarity and Tonicity

A

combination of active drug, preservative, and vehicle usually results in a HYPOTONIC solution (<290 mOsm)*

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12
Q

What is an ophthalmic vehicle?

A

combination of all components of an ophthalmic preparation, minus API

and preservative agent (not intended to enhance delivery)

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13
Q

What is a preservative?

A

a chemical that is added to a drug to PREVENT GROWTH of microorganisms

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14
Q

What is a viscosity- increasing agent?

A

slow-drainage of product from the eye, increasing retention time of active drug

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15
Q

What is an antioxidant

A

prevents or delays deterioration of products by oxygen in the air

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16
Q

What is a wetting agent?

A

reduce surface tension, allowing the drug solution to spread across ocular surface

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17
Q

What is a buffer

A

helps maintain ophthalmic products in the pH rage 6 to 8

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18
Q

What is tonicity agent?

A

help ophthalmic solutions be isotonic with our tear film
- helps prevent ocular irritation and tissue damage
- range of 0.6% to 1.8%

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19
Q

Risk of contamination: ineffective preservative or preservative-free preparations

A

infectious complication risk to the patient if a preparation supports the growth of pathogenic microorganisms

  • caution for immunocompromised
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20
Q

Preservative Effectiveness Test (PET)

A

FDA uses PET as a MINIMUM standard of preservative preformation

Bacterial and fungal organisms used to challenge preservative - compares number of organisms found on a control sample against test sample over 28days or 4 weeks - should have decrease in bacterial count

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21
Q

What is the ideal ophthalmic preservative?

A

bacterial conc. is reduced to 0.1% or less and fungal conc. is at or below original conc.

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22
Q

Ophthalmic Preparations: Chemical class

A

Chemical
Oxidizing Agents
Ionic Buffered

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23
Q

Chemical Detergents

A

OG called Benzalkonium chloride (BZAK)
- detergent
- Toxic effects on corneal epithelium
- *known to cause bacterial cell membrane instability –> cell death

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24
Q

5 Categories of Chemical Preservatives

A

Detergents
Mercurial Derivatives
Amides or Biguanides
Alcohols
misc.

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25
Q

Benzalkonium Chloride (BAC, BAK, BZAK)

A

quaternary ammonium compound (“QUAT”)
- detergent surfactant - mechanism of action is disruption of bacterial cell membranes
- bactericidal agent
- quaternary surfactants are preferred by many manufactures due to stability , excellent antimicrobial properties

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26
Q

Benzethonium Chloride

A

** simiilar properties as Benzalkonium chloride
- detergent surfactant

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27
Q

Polyquaternium-1 (Poly Quad)

A

derivative of BZAK - also a detergent
- similar bactericidal mech as BZAK involving lysis or disruption of cell membrane
- Less toxic than BZAK

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28
Q

What is Thimerosal?

A
  • mercurial compound that blocks or inhibits microbial metabolism
  • patients can develop *contact sensitivity and allergies to thimerosal which may take weeks or months
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29
Q

Polyaminopropyl Biguanide (PAPB)

A
  • bactericidal - high molecular weight biguanide
  • high molecular weight prevents absorption into contact lens matrix
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30
Q

Chlorobutanol

A

alcohol based compound - considered detergent preservative
- bactericidal
- less effective than BZAK, so typically combined with EDTA
- no allergic reactions with prolonged use

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31
Q

Benzyl Alcohol

A
  • alcohol preservative - cellular lysis
  • should not be used to wet and insert lenses due to hypersensitivity reactions
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32
Q

Sorbic Acid (Misc)

A
  • organic acid - less toxic than other chemical preservatives
  • produces low incidence of hypersensitivity reactions is considered less toxic than other chemical preservs.
  • does not cause toxic reactions
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33
Q

Methylparaben and Propylparaben (parabens)

A
  • referred as paraben esters
  • often two or more parabens are included in the same product - usually combined!
  • blocks microbial metabolism
  • can cause allergic reactions and cross react with PABA esters
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34
Q

Disodium EDTA

A
  • chelating agent that binds to divalent cations
  • has antioxidant properties
  • disrupts cell membranes

-*can cause contact Dermatitis
-assists the action of thimerosal, BAC, chlorobutanol, and other agents

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35
Q

Stabilized Oxychlor-Complex (purite) and sodium perborate (GenAqua)

A
  • oxidative preservative systems
  • can be neutralized by mammalian cells, and do no accumulate (contrast to chemical preserv)
  • less toxic than chemical preservatives
36
Q

Oxychloro-complex (purite)

A

dissipates into water and sodium chloride (NaCl) on exposure to light

37
Q

Sodium perborate (Gen-Aqua)

A

converted to hydrogen peroxide and then into oxygen and water

38
Q

Ion-Buffered Preservatives

A

SofZia
- breaks up into innate ingredients
- used in Travatan Z (travoprosts)

39
Q

Viscosity-Increasing Agents

A

Slow drainage of the product from the eye –> increasing retention time

40
Q

Carbopol Gels (polyacrylic acids)
-Viscosity Increasing Agent

A
  • Polyacrylic acid or carbomer is generic name for synthetic high molecular weight polymers of acrylic acid
  • compounds with pseudoplastic properties
    -viscoelastic agents exhibit both viscous and elastic characteristics
  • sheer thinning polymers
41
Q

Hydroxypopyl Methylcellulose (Hypromellose)
Viscosity Increasing Agent

A
  • cellulose derivative and viscoelastic polymer
  • polysaccaride
  • prolongs tear film wetting time
42
Q

Carboxymethylcellulose (CMC)
Viscosity Increasing Agent

A
  • cellulose derivative and viscoelastic polymer
  • cellulose is polysaccharide
43
Q

Carboxymethylcellulose (CMC)
Viscosity Increasing Agent

A
  • cellulose derivative and viscoelastic polymer
  • cellulose is polysaccharide
44
Q

Polyxamer (Viscosity Increasing Agent)

A

viscosity enhancer/builder and wetting agent

45
Q

Polyethylene glycol (PEG) and propylene glycol

A

Viscosity Increasing Agent

46
Q

Antioxidant Agents (Inactive Ingredients)

A

Prevents or delay deterioration of products by oxygen in the air

  • *EDTA
  • *Sodium bisulfites (“sulfites”)
  • *Sodium metabisulfite (“sulfites”)
  • thiourea
47
Q

Disodium EDTA*

A
  • chelating agent that binds divalent cations
  • antioxidative properties
  • disrupts cell membrane
  • can cause contact dermatitis
  • assists the action of thimerosal, BAC, chlorobutanol, and other agents
48
Q

“Sulfites”
sodium bisulfite and sodium metabisulfite

A

Antioxidant agent - prevent or delay deterioration of products by oxygen in the air

49
Q

Wetting Agents (inactive ingredients)

A
  • reduces surface tension, allows drug solution to spread across the ocular surface
  • overlaps with some viscosity-increasing agents
  • *polysorbate
  • *poloxamer
  • *tyloxapol
50
Q

Buffers (inactive ingredient)

A
  • maintains ophthalmic products in pH range 6 to 8
  • some overlaps with tonicity agents
  • acetic acid, boric acid, hydrochloric acid, phosphoric acids
  • potassiums salts
  • sodiums salts - reference base is sodium hydroxide
51
Q

tonicity agents (inactive ingredients

A
  • agents help ophthalmic solutions to be a isotonic
  • dextran 40
  • dextran 80
  • glycerin
  • propylene glycol
52
Q

Inactive Ingredients as Drug Delivery Systems

A

drug delivery systems are considered inactive ingredients, may be viewed as vehicles *for the delivery of therapeutic agents

  • solutions
  • suspensions
  • emulsions (aka colloid)
  • ointment bases
  • gel-type systems
53
Q

what are solutions

A

homogenous mixture of two+ substances
- *most eyedrops are solutions

  • solute is dissolved in solvent
54
Q

What are suspensions

A

heterogeneous mixture of two substances containing solid particles

  • *need to shake or agitate ocular suspensions
55
Q

What are Emulsions

A

(aka colloid)
- mixture of two or more liquid normally immiscible (unmixable)

56
Q

what are ointment bases?

A

typically mixtures of white petrolatum and liquid mineral oil with or without water-miscible agents such as Lanolin

  • increases ocular contact time
  • mineral oil added to allow vehicle to melt at body temp + lanolin to absorb water
57
Q

What are gel-forming systems?

A
  • use of large molecules that demonstrate *reversible phase changes or transitions
  • aqueous drop in eye reversible gels on contact with pre-corneal tear film
  • enhances corneal penetration + prolongs action
58
Q

Targeted Drug Delivery Systems

A
  • may involve higher degree of engineering

*Liposomes
*nanoparticles
*cyclodextrins
*soft-contact Lens
*device inserts
*intraocular medication delivery (intravitreal implants)

59
Q

What are Liposomes (TDDS)

A
  • microscopic vesicles composed of lipid bilayers surround aqueous compartments – prolongs drug effects
  • entraps both hydrophilic and hydrophobic drugs
60
Q

what are nanoparticles (TDDS)

A

polymeric colloidal particles that provide extended duration drug delivery system

  • drug loaded nanoparticles can be *nanocapsules or nanospheres
  • nanorobotics uses nanotechnology to develop microscopic robots
61
Q

What are cyclodextrins

A
  • cyclic oligosaccharides – water soluble , which can incorporate lipid-soluble drugs in their centers
  • hydrophilic outer and lipophilic central cavity
  • improves solubility and stability
61
Q

What are cyclodextrins

A
  • cyclic oligosaccharides – water soluble , which can incorporate lipid-soluble drugs in their centers
  • hydrophilic outer and lipophilic central cavity
  • improves solubility and stability
62
Q

Soft Contact lenses

A
  • can absorb drugs from solutions and slowly release them when placed on eye
63
Q

device inserts

A

polymers with drug in matrix

64
Q

Topical Administration (ocular/ophthalmic admin)

A
  • most common route of admin for ophthalmic drugs
  • pros: convenient, simple, non-invasive
  • *requires Patient Education regarding risk of contamination
65
Q

Drug Clearance of Ocular Topical Admin

A
  • result of drug loss through systemic circulation
  • conju. sac
  • lacrimal drainage
  • episclera
66
Q

Solutions are the most common topical mode of delivery

A

solutions & suspensions&raquo_space;> preferred ointments

  • advantages of solutions: ease of instillation, little interference with vision and few potential complications
67
Q

Solution disadvantages

A
  • brief contact time (short ocular surface time)
  • imprecise amt of drugs delivered
  • potent. for contamination
  • potent. for ocular injury via dropper tip
68
Q

Suspension Advantages

A
  • improved contact time over solutions – adheres to conj. to act as reservoir
69
Q

Suspension disadvantages

A
  • need to shake bottle prior to administration
  • imprecise amt of drugs delivered
  • ineffective resuspension of medication after bottle agitation based on patient technique (patient variation)
70
Q

Are all suspensions created equal? are generic suspensions comparable to trade name suspensions

A

cannot directly measure in human eye – assuming drug absorption rates are similar b/n human and animal eyes

Degree of impact of different vehicle formulations - degree of re-suspension varies among preparations*
ex: *Prednisolone acetate 1% ophthalmic suspension (various generic, *Pred Forte, Omnipred, Pred Mild)

  • optometrist should consider products with poorly suspended ingr. can compromise the treatment
71
Q

Ophthalmic Emulsion (new delivery vehicles)

A

Advantages – no need to shake bottle prior to administration
- improved contact time – *if preservative free = one time use

Ex: *difluprednate 0.05%, opth. emulsion (Durazol) & *Cyclosporine 0.05% ophth. emulsion (restasis)

72
Q

*Difluprednate 0.05% ophth. emulsion Durazol

A

Indication - inflammation/pain associated with ocular surgery and endogenous anterior uveitis
Pharmacology – most potent opthalmic steroid

73
Q

*Cyclosporine 0.05% ophth. emulsion Restatsis

A

indication – keratoconjunctivitis sicca
Pharmacology – considered immunosuppressant agent - acts as partial immunomodulator

74
Q

Opthalmic Ointments Advantages

A

ease of installation
non-invasive
*prolonged contact time

75
Q

Ophthalmic ointment disadvantage

A
  • blurred vision
  • contact dermatitis – due to longer contact time
  • caution patients with corneal ulcers or large overhanging margins
76
Q

Packing/Storage + installation of Ophth. Ointments

A
  • usually packaged into small tubes + protective box – has recomm. temperature
  • apply solution prior to applying ointment
  • emphasize on how to keep ointment tube tip sterile
77
Q

Potential usage of ophthalmic ointments

A
  • immediate after intraocular surgery to minimize frequent anti-biotic and steroid administration
  • superficial corneal abrasions and corneal ulcers
78
Q

Sprays

A
  • alternative ophthalmic administration
  • most commonly seen in lid scrub products *
79
Q

Lid Scrubs

A

application is direct on lid margines
- treat seborrheic or infectious blepharitis
- cleaning of lid margins

80
Q

Injectable Ocular Administrations

A

when higher conc. of drugs are required - antibiotics or sterioids

81
Q

Solid Delivery Devices / Drug Release Systems

A

one of the significant probs with delivery of drug in solution is that *drug is PULSED, initial period of overdose then period of relative underdose

82
Q

examples of solid delivery devices

A
  • soft contact lens - absorbs drugs from solutions and slowly releases
  • filter paper strips
  • cotton pledgets
  • device inserts - artificial tear inserts – polymers with drug matrix
  • intraocular medication delivery
83
Q

Soft Contact lens

A
  • absorbs drugs from solutions and slowly releases
  • silicone hydrogel lenses deliver maximum oxygen to the cornea
  • lens thickness is a factor for drug delivery
  • Drug release follows first order kinetics for older lenses
    -    in technology – incorp. drug into lens matrix for controlled release rate = zero-order kinetics
84
Q

Artificial tear Inserts

A

*pellet of hydroxypropyl cellulose - placed in the inferior conjunctival fornix

Spring OD1- Pharmacology (7 decks)

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