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Ophthalmology > Ocular drugs > Flashcards

Ocular drugs Flashcards

1
Q

How can a drug be delivered to ocular tissue?

A

Locally (eye drops, ointments, periocular injections, intraocular injections) and systemically (orally, IV).

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2
Q

What is the most commonly used route for ocular drug administration?

A

The topical route.

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3
Q

What factors influence the absorption of topically instilled drugs?

A

Elimination by nasolacrimal drainage, time in the conjunctival cul-de-sac & precorneal tear film, drug binding to tear proteins, drug metabolism by tear & tissue proteins, and rate of diffusion across the cornea & conjunctiva.

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4
Q

Describe the distribution process of ocular drugs.

A

Transcorneal absorption, accumulation in aqueous humor, distribution to intraocular structures, trabecular meshwork pathway, and distribution to systemic circulation.

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5
Q

What is significant in the metabolism of ocular drugs?

A

Enzymatic biotransformation, particularly by esterases, with examples including prodrugs like dipivefrin hydrochloride and latanoprost.

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6
Q

What are some methods of topical ocular drug delivery?

A

Drops, ointments, and gels.

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7
Q

What are periocular injections and their examples?

A

Injections that reach behind the iris-lens diaphragm better than topical application, such as subconjunctival, subtenon, peribulbar, and retrobulbar

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8
Q

What is the purpose of intraocular injections and examples?

A

For anterior segment surgery or infections, such as intracameral acetylcholine during cataract surgery and intravitreal antibiotics for endophthalmitis.

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9
Q

What are sustained-release devices in ocular drug delivery?

A

Devices that deliver medication at a steady-state level, such as Ocusert delivering pilocarpine and Timoptic XE delivering timolol.

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10
Q

What factors influence systemic drug penetration into ocular tissue?

A

Lipid solubility, protein binding, and ocular inflammation.

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11
Q

What are the advantages and limitations of topical ocular drug administration?

A

Convenient, economical, relatively safe. Limitations: Compliance, corneal & conjunctival toxicity, nasal mucosal toxicity, systemic side effects from nasolacrimal absorption.

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12
Q

What is the special utility of sub-conjunctival, sub-Tenon’s, and retrobulbar injections?

A

Useful for anterior segment infections, posterior uveitis, and cystoid macular edema (CME).

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13
Q

What are the potential complications of sub-conjunctival, sub-Tenon’s, and retrobulbar injections?

A

Local toxicity, globe perforation, optic nerve trauma, central retinal artery or vein occlusion.

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14
Q

What are intraocular injections and when are they used?

A

Injections directly into the eye, used for anterior segment surgery or infections. Examples include intracameral acetylcholine during cataract surgery and intravitreal antibiotics for endophthalmitis.

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15
Q

What is the use of intravitreal injections?

A

To provide an immediate local effect for conditions like macular edema or diabetic retinopathy (DR).

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16
Q

What are the advantages of periocular injections?

A

They bypass the conjunctival and corneal epithelium, useful for drugs with low lipid solubility, such as penicillins and steroids.

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17
Q

How does drug concentration and solubility affect local drug penetration into ocular tissue?

A

Higher concentration results in better penetration. Example: Pilocarpine 1-4%, but limited by reflex tearing.

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18
Q

What is the role of viscosity in drug penetration into ocular tissue?

A

Addition of methylcellulose and polyvinyl alcohol increases drug penetration by increasing contact time with the cornea and altering the corneal epithelium.

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19
Q

How does lipid solubility influence local drug penetration into the eye?

A

Higher lipid solubility results in more penetration.

20
Q

What effect do surfactants have on drug penetration into ocular tissue?

A

Preservatives like benzylkonium and thiomersal alter cell membranes in the cornea and increase drug permeability.

21
Q

How does the pH of a drug influence its penetration into ocular tissue?

A

he normal tear pH is 7.4. If the drug pH is much different, it can cause reflex tearing, affecting penetration.

22
Q

Explain the influence of drug tonicity on ocular penetration.

A

When an alkaloid drug is in a relatively alkaloid medium, the proportion of the uncharged form increases, resulting in more penetration.

23
Q

What is a retrobulbar injection and what conditions is it used for?

A

An injection behind the eyeball, used for conditions like optic neuritis, papillitis, and posterior uveitis, as well as for anesthesia.

24
Q

What are subtenon injections and their types?

A

Injections into the space between the sclera and the Tenon’s capsule. Types include anterior subtenon (for diseases anterior to the lens) and posterior subtenon (for diseases posterior to the lens).

25
Q

What is a subconjunctival injection and when is it used?

A

An injection given under the conjunctiva, used to achieve higher drug concentration, particularly for drugs that cannot penetrate the cornea due to large size.

26
Q

What are the risks and complications associated with periocular injections?

A

Local toxicity, globe perforation, optic nerve trauma, and central retinal artery or vein occlusion.

27
Q

What are intraocular injections?

A

Injections delivered directly into the eye, specifically into the anterior segment or the vitreous cavity.

28
Q

When are intracameral injections typically used?

A

During anterior segment surgery or to treat infections. Example: Intracameral acetylcholine (Miochol) during cataract surgery.

29
Q

What conditions are intravitreal injections used to treat?

A

Conditions like macular edema, endophthalmitis, and diabetic retinopathy (DR).

30
Q

Provide an example of an intravitreal injection used for macular edema.

A

Intravitreal steroids.

31
Q

What is a common use of intravitreal antibiotics?

A

Treating endophthalmitis.

32
Q
A
33
Q

What is a primary use of intravitreal anti-VEGF injections?

A

Treating diabetic retinopathy (DR).

34
Q

What are the potential complications of intraocular injections?

A

Corneal toxicity and relatively short duration of action

35
Q

What is an advantage of using intravitreal injections?

A

They provide an immediate local effect.

35
Q

What are sustained-release devices in ocular drug delivery?

A

Devices that deliver a consistent supply of medication at a steady-state level over an extended period.

36
Q

What is an example of a sustained-release device delivering pilocarpine?

A

Ocusert.

37
Q

Which sustained-release device delivers timolol?

A

Timoptic XE.

38
Q

What is a sustained-release intraocular device used for delivering ganciclovir?

A

A ganciclovir sustained-release intraocular device.

39
Q

What are collagen shields used for in ocular drug delivery?

A

They are used as sustained-release devices for delivering medication

40
Q

What is the primary benefit of using sustained-release devices for ocular drug delivery?

A

They maintain therapeutic drug levels over an extended period, reducing the frequency of administration and improving compliance.

41
Q

What are systemic drugs in the context of ocular drug delivery?

A

Drugs administered orally or intravenously that affect ocular tissues through systemic circulation.

42
Q

How does lipid solubility influence the penetration of systemic drugs into ocular tissue?

A

Drugs with higher lipid solubility have better penetration into ocular tissues.

43
Q

What role does protein binding play in the effectiveness of systemic drugs on ocular tissue?

A

Drugs with lower protein binding are more effective as they have higher free concentrations available to penetrate ocular tissues.

44
Q

How does ocular inflammation affect the penetration of systemic drugs?

A

Ocular inflammation increases the penetration of systemic drugs into ocular tissues.

45
Q

Name two routes of administration for systemic drugs in ocular treatments.

A

Oral and intravenous (IV).

46
Q

What is a common scenario where systemic drugs are preferred for ocular treatment?

A

When local delivery methods are insufficient or not feasible, such as in severe infections or inflammatory conditions.

Ophthalmology (16 decks)

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