Recent Challenges and Advances in Ophthalmic Drug Delivery 4. Preparation for various diagnostic...
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Vol. 1 No. 4 2012 Online Available at www.thepharmajournal.com
THE PHARMA INNOVATION
Vol. 1 No. 4 2012 www.thepharmajournal.com Page | 1
Recent Challenges and Advances in Ophthalmic Drug Delivery System
K. P. Sampath Kumar1*, Debjit Bhowmik2, Shravan Paswan3, Shweta Srivastava4 1. Coimbatore medical college, Coimbatore, Tamil Nadu, India 2. Department of pharmaceutical sciences, Karpagam University, Coimbatore, Tamil Nadu, India 3. Advance Institute of Biotech and Paramedical Sciences, Kanpur, Uttar Pradesh, India 4. Hygia Institute of Pharmaceutical Education and Research, Lucknow, Uttar Pradesh, India Ocular drug delivery is one of the most fascinating and challenging tasks facing the Pharmaceutical researchers. One of the major barriers of ocular medication is to obtain and maintain a therapeutic level at the site of action for prolonged period of time. Ocular drug delivery is hampered by the barriers protecting the eye. The bioavailability of the active drug substance is often the major hurdle to overcome. Conventional ocular dosage form, including eye drops, are no longer sufficient to combat ocular diseases. This article reviews the constraints with conventional ocular therapy, essential factors in ocular pharmacokinetics, and explores various approaches like eye ointments, gel, viscosity enhancers, prodrug, penetration enhancers, microparticles, liposomes, niosomes, ocular inserts, implants, intravitreal injections, nanoparticles, nanosuspension, microemulsion, in situ-forming gel, iontophoresis, and periocular injections to improve the ocular bioavailability of drug and provide continuous and controlled release of the drug to the anterior and posterior chamber of the eye and selected pharmacological future challenges in ophthalmology. In near future, a great deal of attention will be paid to develop noninvasive sustained drug release for both anterior and posterior segment eye disorders. Current momentum in the invention of new drug delivery systems hold a promise toward much improved therapies for the treatment of vision-threatening disorders. Keyword: Ophthalmic Drug Delivery System
INTRODUCTION: Eye-drops are the conventional dosage forms that account for 90% of currently accessible ophthalmic formulations. Despite the excellent acceptance by patients, one of the major problems encountered is rapid
Corresponding Author’s Contact information: K.P. Sampath Kumar* Coimbatore medical college, Coimbatore, Tamil Nadu, India E-mail: firstname.lastname@example.org
precorneal drug loss. To improve ocular drug bioavailability, there is a significant effort directed towards new drug delivery systems for ophthalmic administration. This chapter will focus on three representative areas of ophthalmic drug delivery systems: polymeric gels, colloidal systems, cyclodextrins and collagen shields. Hydrogels generally offer a moderate improvement of ocular drug bioavailability with the disadvantage of blurring of vision. In situ activated gel-forming systems are preferred as
K. P. Sampath Kumar*, Debjit Bhowmik, Shravan Paswan, Shweta Srivastava
Vol. 1 No. 4 2012 www.thepharmajournal.com Page | 2
they can be delivered in drop form with sustained release properties. Colloidal systems including liposomes and nanoparticles have the convenience of a drop, which is able to maintain drug activity at its site of action and is suitable for poorly water-soluble drugs. Among the new therapeutic approaches in ophthalmology, cyclodextrins represent an alternative approach to increase the solubility of the drug in solution and to increase corneal permeability. Finally, collagen shields have been developed as a new continuous- delivery system for drugs that provide high and sustained levels of drugs to the cornea, despite a problem of tolerance. It seems that new tendency of research in ophthalmic drug delivery systems is directed towards a combination of several drug delivery technologies. There is a tendency to develop systems which not only prolong the contact time of the vehicle at the ocular surface, but which at the same time slow down the elimination of the drug. Combination of drug delivery systems could open a new directive for improving results and the therapeutic response of non-efficacious systems. One of the ways to optimize ocular drug delivery is to prolonge precorneal drug residence time. This review focusses on recent findings on the formulation effects in ocular drug bioavailability, employing polymers for the preparation of hydrogels, bioadhesive dosage forms, in situ gelling systems and colloidal systems including liposomes and nanoparticles. The results observed suggested that mucoadhesion or bioadhesion played a role in the sustained action of drugs more significantly compared to non-mucoadhesive polymers. Encapsulation of drugs in liposomes and nanoparticles was correlated to an increase of the drug concentration in the ocular tissues. However, all the results described suggest that the physico- chemical properties of the encapsulated drug have a significant influence on the effect with the carrier. The results suggest also that the superficial charge, the binding type of the drug onto the nanoparticles and the nature of the polymer were the most important factors regarding the improvement of the therapeutic response of the drug.
OPHTHALMIC DOSAGE FORM 7
Ophthalmic preparations are sterile products essentially free from foreign particles, suitably compounded and packaged for instillation in to the eye. The following dosage forms have been developed to ophthalmic drugs. Some are in common use, some are merely experimental, and others are no longer used. Ocular drug delivery presents unique challenges and opportunities. Eye tissues can be accessed directly with relative ease using topical eye drops. However, the loading and ocular absorption of drugs are limited using traditional solution and suspension formulations, particularly for compounds with low aqueous solubility. For such compounds, delivery to the posterior ocular tissues, including the retina and choroid, can be particularly problematic. The need for formulations that increase the topical ocular absorption of poorly soluble compounds remains largely unmet, precluding the development of otherwise promising medicines for glaucoma, age-related macular degeneration (AMD), diabetic retinopathy, infections, and other eye diseases. Consequently, Bend Research has developed an amorphous nanoparticle platform for topical ocular delivery of low solubility compounds. It enhances the bioavailability of ocular drugs by enabling high drug loadings, increased drug solubility and drug time on the ocular surface, and rapid drug dissolution. These factors produce higher drug concentrations in the primary target tissues—e.g., the irisciliary body (ICB), retina, and choroid—than can be achieved with conventional formulations. In turn, these high concentrations can lead to longer duration of action and decreased dosing frequency. This advance should relax current constraints on new drug discovery for properties such as solubility and lipophilicity and should allow for greater focus on potency and selectivity.
K. P. Sampath Kumar*, Debjit Bhowmik, Shravan Paswan, Shweta Srivastava
Vol. 1 No. 4 2012 www.thepharmajournal.com Page | 3
1. Aqueous eye drops
2. Oily eye drops
3. Eye ointments
4. Eye lotions
5. Paper strips
7. Hydro gel contact lenses
8. Collagen shields
9. Ophthalmic rods
1. They are easily administered by the nurse 2. They are easily administered by the patient
himself. 3. The drug is in a solved state and may be
immediately active. 4. They have the quick absorption and effect.
1. The very short time the solution stays at the eye surface.
2. Its poor bioavailability 3. The instability of the dissolved drug 4. The necessity of using preservatives. EYE DROPS These are the most common of administering a drug to the eye. All ingredients are completely in solution, uniformity is not a problem TYPES:
1. Solutions 2. Suspensions 3. Emulsions
ADVNTAGES: 1. Decrease the amount of fluid forming in
the eye 2. Increase the ability of the eye to drain
fluid 3. Administering medications for the
treatment of eye disorders 4. Preparation for various diagnostic
procedures during eye examinations 5. There is less risk of side effects than with
oral medicines 6. Used during an examination and
administered as a local anaesthetic prior to a medical procedure
DISADVANTAGES: 1. A red eye, irritation 2. Fatigue or decreased energy 3. Skin rash (especially in individuals with
known allergy to sulpha drugs) 4. Change in taste (especially with
carbonated beverage 5. A change in eye colour (mostly in hazel or
blue to green eyes) 6. Increase in thickness and number of
eyelashes 7. Blurred vision 8. Headache.
EXCIPIENTS USED IN OPHTHALMIC SOLUTIONS8
All raw materials used in the compounding of ophthalmic solutions must be of the highest quality available. Each component must be established and verified for