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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
Benzalkonium Chloride (BAC, BAK, BZAK)
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
26
Benzethonium Chloride
** simiilar properties as Benzalkonium chloride - detergent surfactant
27
Polyquaternium-1 (Poly Quad)
derivative of BZAK - also a detergent - similar bactericidal mech as BZAK involving lysis or disruption of cell membrane - Less toxic than BZAK
28
What is Thimerosal?
- mercurial compound that blocks or inhibits microbial metabolism - patients can develop *contact sensitivity and allergies to thimerosal which may take weeks or months
29
Polyaminopropyl Biguanide (PAPB)
- bactericidal - high molecular weight biguanide - high molecular weight prevents absorption into contact lens matrix
30
Chlorobutanol
alcohol based compound - considered detergent preservative - bactericidal - less effective than BZAK, so typically combined with EDTA - no allergic reactions with prolonged use
31
Benzyl Alcohol
- alcohol preservative - cellular lysis - should not be used to wet and insert lenses due to hypersensitivity reactions
32
Sorbic Acid (Misc)
- 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
33
Methylparaben and Propylparaben (parabens)
- 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
34
Disodium EDTA
- 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
35
Stabilized Oxychlor-Complex (purite) and sodium perborate (GenAqua)
- oxidative preservative systems - can be neutralized by mammalian cells, and do no accumulate (contrast to chemical preserv) - less toxic than chemical preservatives
36
Oxychloro-complex (purite)
dissipates into water and sodium chloride (NaCl) on exposure to light
37
Sodium perborate (Gen-Aqua)
converted to hydrogen peroxide and then into oxygen and water
38
Ion-Buffered Preservatives
SofZia - breaks up into innate ingredients - used in Travatan Z (travoprosts)
39
Viscosity-Increasing Agents
Slow drainage of the product from the eye --> increasing retention time
40
Carbopol Gels (polyacrylic acids) -Viscosity Increasing Agent
- 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
Hydroxypopyl Methylcellulose (Hypromellose) Viscosity Increasing Agent
- cellulose derivative and viscoelastic polymer - polysaccaride - prolongs tear film wetting time
42
Carboxymethylcellulose (CMC) Viscosity Increasing Agent
- cellulose derivative and viscoelastic polymer - cellulose is polysaccharide
43
Carboxymethylcellulose (CMC) Viscosity Increasing Agent
- cellulose derivative and viscoelastic polymer - cellulose is polysaccharide
44
Polyxamer (Viscosity Increasing Agent)
viscosity enhancer/builder and wetting agent
45
Polyethylene glycol (PEG) and propylene glycol
Viscosity Increasing Agent
46
Antioxidant Agents (Inactive Ingredients)
Prevents or delay deterioration of products by oxygen in the air - *EDTA - *Sodium bisulfites ("sulfites") - *Sodium metabisulfite ("sulfites") - thiourea
47
Disodium EDTA*
- 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
"Sulfites" sodium bisulfite and sodium metabisulfite
Antioxidant agent - prevent or delay deterioration of products by oxygen in the air
49
Wetting Agents (inactive ingredients)
- reduces surface tension, allows drug solution to spread across the ocular surface - overlaps with some viscosity-increasing agents - *polysorbate - *poloxamer - *tyloxapol
50
Buffers (inactive ingredient)
- 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
tonicity agents (inactive ingredients
- agents help ophthalmic solutions to be a isotonic - dextran 40 - dextran 80 - glycerin - propylene glycol
52
Inactive Ingredients as Drug Delivery Systems
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
what are solutions
homogenous mixture of two+ substances - *most eyedrops are solutions - solute is dissolved in solvent
54
What are suspensions
heterogeneous mixture of two substances containing *solid particles* - *need to shake or agitate ocular suspensions
55
What are Emulsions
(aka colloid) - mixture of two or more liquid normally immiscible (unmixable)
56
what are ointment bases?
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
What are gel-forming systems?
- 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
Targeted Drug Delivery Systems
- may involve higher degree of engineering *Liposomes *nanoparticles *cyclodextrins *soft-contact Lens *device inserts *intraocular medication delivery (intravitreal implants)
59
What are Liposomes (TDDS)
- microscopic vesicles composed of lipid bilayers surround aqueous compartments -- prolongs drug effects - entraps both hydrophilic and hydrophobic drugs
60
what are nanoparticles (TDDS)
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
What are cyclodextrins
- cyclic oligosaccharides -- water soluble , which can incorporate lipid-soluble drugs in their centers - hydrophilic outer and lipophilic central cavity - improves solubility and stability
61
What are cyclodextrins
- cyclic oligosaccharides -- water soluble , which can incorporate lipid-soluble drugs in their centers - hydrophilic outer and lipophilic central cavity - improves solubility and stability
62
Soft Contact lenses
- can absorb drugs from solutions and slowly release them when placed on eye
63
device inserts
polymers with drug in matrix
64
Topical Administration (ocular/ophthalmic admin)
- most common route of admin for ophthalmic drugs - pros: convenient, simple, non-invasive - *requires Patient Education regarding risk of contamination
65
Drug Clearance of Ocular Topical Admin
- result of drug loss through systemic circulation - conju. sac - lacrimal drainage - episclera
66
Solutions are the most common topical mode of delivery
solutions & suspensions >>> preferred ointments - advantages of solutions: ease of instillation, little interference with vision and few potential complications
67
Solution disadvantages
- brief contact time (short ocular surface time) - imprecise amt of drugs delivered - potent. for contamination - potent. for ocular injury via dropper tip
68
Suspension Advantages
- improved contact time over solutions -- adheres to conj. to act as reservoir
69
Suspension disadvantages
- 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
Are all suspensions created equal? are generic suspensions comparable to trade name suspensions
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
Ophthalmic Emulsion (new delivery vehicles)
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
*Difluprednate 0.05% ophth. emulsion Durazol
Indication - inflammation/pain associated with ocular surgery and endogenous anterior uveitis Pharmacology -- most potent opthalmic steroid
73
*Cyclosporine 0.05% ophth. emulsion Restatsis
indication -- keratoconjunctivitis sicca Pharmacology -- considered immunosuppressant agent - acts as partial immunomodulator
74
Opthalmic Ointments Advantages
ease of installation non-invasive *prolonged contact time
75
Ophthalmic ointment disadvantage
- blurred vision - contact dermatitis -- due to longer contact time - caution patients with corneal ulcers or large overhanging margins
76
Packing/Storage + installation of Ophth. Ointments
- 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
Potential usage of ophthalmic ointments
- immediate after intraocular surgery to minimize frequent anti-biotic and steroid administration - superficial corneal abrasions and corneal ulcers
78
Sprays
- alternative ophthalmic administration - most commonly seen in lid scrub products *
79
Lid Scrubs
application is direct on lid margines - treat seborrheic or infectious blepharitis - cleaning of lid margins
80
Injectable Ocular Administrations
when higher conc. of drugs are required - antibiotics or sterioids
81
Solid Delivery Devices / Drug Release Systems
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
examples of solid delivery devices
- 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
Soft Contact lens
- 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
Artificial tear Inserts
*pellet of hydroxypropyl cellulose - placed in the inferior conjunctival fornix

Spring OD1- Pharmacology (7 decks)

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