BIOFARMASI SEDIAAN MATA

Summary

This video script discusses bioavailability in ocular drug formulations, focusing on the challenges and solutions for drug penetration in the eye. It explains how the cornea’s unique structure, composed of lipophilic and hydrophilic layers, affects drug absorption. The lecture also covers the importance of drug characteristics such as solubility and molecular size in achieving effective drug delivery. Further, it highlights the role of topical eye treatments and how factors like pH, osmolarity, and viscosity influence the efficiency of the medication. The session aims to educate on optimizing ocular drug delivery for better therapeutic outcomes.

Takeaways

• 😀 The study of bio-pharmaceuticals for ocular formulations focuses on overcoming the challenges of drug penetration into the eye.
• 😀 Drug penetration is influenced by two main factors: the opposite directions of drug movement and the cornea's unique structure, which consists of lipophilic and hydrophilic layers.
• 😀 The cornea has an epithelial layer that is lipophilic (fat-soluble), and a stromal layer that is hydrophilic (water-soluble), complicating drug absorption.
• 😀 Effective drug formulation for the eye requires a thorough understanding of the eye's anatomy and physiology, including the role of the cornea and conjunctiva.
• 😀 The sclera, choroid, and retina play significant roles in drug absorption and delivery within the eye, with minimal blood flow in the sclera.
• 😀 Topical ocular formulations, such as eye drops, face challenges in drug absorption due to the presence of tear fluid and eyelid blinking.
• 😀 Two main pathways exist for drug absorption: through the corneal epithelium and via the scleral capillaries.
• 😀 The drug's solubility (hydrophilic or lipophilic) and the method of administration significantly affect its absorption speed and effectiveness in the eye.
• 😀 Factors affecting ocular drug absorption include pH, viscosity, surfactants, and the physical-chemical properties of the drug.
• 😀 The ideal pH for eye formulations is around 7.4, matching the natural pH of the eye, and formulations should be isotonic to prevent irritation.

Q & A

What are the two main factors that make it difficult for drugs to penetrate the eye?

The two main factors are: 1) the opposite direction of drug penetration, where the drug moves from outside to inside the eye while the tear flow moves outward, and 2) the unique structure of the cornea, which consists of both lipophilic and hydrophilic layers, making it harder for drugs to penetrate.

How does the cornea's structure affect drug absorption?

The cornea has a unique structure composed of two main layers: the outer epithelial layer (lipophilic) and the inner stroma (hydrophilic). This dual structure makes it challenging for drugs to pass through, as they must be able to traverse both types of tissue.

Why is it important to understand the anatomy and physiology of the eye when developing drug formulations?

Understanding the eye's anatomy and physiology is crucial for designing drug formulations that can effectively penetrate the eye tissues and target the intended area. It helps in identifying the best routes for drug absorption and addressing barriers like the corneal structure and tear flow.

What is the role of the sclera, conjunctiva, and choroid in drug delivery to the eye?

The sclera provides limited blood supply to the eye, the conjunctiva is where topical medications are applied, and the choroid receives adequate blood flow to nourish the eye tissues. Together, these layers influence the effectiveness and absorption of topical or systemic drugs.

How does the use of topical eye drops influence drug absorption in the eye?

Topical eye drops are designed to increase the contact time between the drug and the corneal surface, thus enhancing the drug's penetration. The effectiveness is also influenced by factors like the formulation's viscosity and the frequency of application.

What are the differences between systemic and topical drug delivery to the eye?

Topical delivery involves directly applying a drug to the eye surface, while systemic delivery administers the drug through oral or parenteral routes, where it then enters the bloodstream and eventually reaches the eye. Systemic delivery requires the drug to pass through various barriers before reaching the eye.

What role does diffusion play in ocular drug penetration?

Diffusion is a key process in ocular drug penetration. The drug moves from an area of higher concentration to lower concentration through the cornea, and this process is influenced by the drug's solubility, particle size, and the characteristics of the ocular tissues.

How do molecular characteristics affect drug penetration in the eye?

Molecular characteristics, such as lipophilicity and hydrophilicity, play a significant role in ocular drug penetration. Lipophilic molecules tend to pass through the cornea more easily, while hydrophilic molecules may face more difficulty due to the differing properties of the corneal layers.

What factors influence the bioavailability of ocular drug formulations?

The bioavailability of ocular drug formulations is influenced by factors such as the pH of the solution, the presence of surfactants, the viscosity of the formulation, and the contact time with the corneal surface. These factors can enhance or hinder drug absorption and effectiveness.

Why is the pH of the eye medication important for eye health?

The ideal pH for eye medications is around 7.4, which closely matches the natural pH of the eye. A mismatch in pH can lead to irritation or damage to the corneal and conjunctival tissues, reducing the effectiveness of the treatment and causing discomfort.