Eye lotions are undiluted aqueous solutions, applied to an eye bath, which for first aid purposes. It is may allow a large volume of fluid to flow quickly over the eye.
Formulation: It is iso-osmotic to tears, because compared to eye drops, lotions cause much greater dilution of the lachrymal fluid, hence cause discomfort if not adjusted. Thus there preparations should be very simple as well as the most common eye lotion consists of sterile normal saline. This preparation typifies the requirements of an eye lotion which are: ---------
· Sterile as well as usually containing no preservative.
· Sotonic to lachrymal fluid
· Natural pH
· Large volume but not greater than 200ml
· Non irritant ocular tissue.
Types: The B.P.C. describes two types of lotion: ----------
Sterile aqueous solutions:
· Contains no bactericide.
· Intended for first aid nor other purposes over a maximum period of 24 hr.
· Applied in a single dose container.
Example: Sodium chloride (NaCl) eye lotion B.P.C. used to remove foreign substance from the eye.
Aqueous solutions:
· It contains a bactericide
· Used for intermittent domiciliary administration for up to seven days.
· They are applied in multi-dose container.
Example: Soothing lotions for tried eyes fall into this category.
Characteristics
· Used in large volume(bulk volume) to mechanically remove foreign materials.
· Each container used one time,should be discarded toin 24 hour after opening.
· No need to use any preservative.
e.g sodium bicarbonate eye lotion used in emergency treatment acid burns of the eye.
Disadvantage
Volume drainage is the main problem to an eye lotion.
It is due to
· Shape of the eye(biconvex shaped eyeball)
· The formulation(Bulk volum of eye lotion)
Drainage of the drop through the nasolacrimal system into GI tract begins immediately on instillation.Rapid clearance provides a temporal barrier to drug delivery.
Decrease in drop size 20 and less decreases drainage rate as well as increases the ocular contact(residence) time as well as bioavailability.Practically there are difficulty in design safe eye droppers that will deliver volumes as small as 5 or 10 μl.On the other has well as this main disadvantage to eye lotion is,bulk volume is used to mechanically remove foreign materials.
Following installation of even small drop, normal lachrymation will immediately begin to dilute as well as wash away drug.It is known as volume drainage to eye lotion preparation.
Difference between Eye drops as well as Eye lotions
Eye drop | Eye lotion |
1. Less amount used | 1. Used in a large vplume to mechanically remove foreign materials. |
2. Medicament is necessary | 2. Medicament is not necessary |
3. Isotonicity not essential | 3. Must be isotonic to tears due to larger amount use |
4. It is used as treatment purpose | 4. It is used for the first aid or irrigation or washing purpose |
5. dilution is not strictly considered | 5. It must be undiluted |
6. This is domiciliary use, should be discarded toin 4 weeks after first opening. But in hospital wards should be discarded 1 week after opening. | 6. Should be discarded toin 24 hr. after first opening. |
SUSPENSION
If the drug is not sufficientlsy soluble,it can be formulated as a suspension.A suspension may also can be desired to improve stability,bioavailability,or efficacy.The major topical ophthalmic suspensions are the steroid anti-inflammatory agents prednisolone acetate,dexamethasone,fluorometholone,as well as rimexolone.Water-soluble salts of prednisolone phosphate as well as dexamethasone phosphate are available;however,they have a lower steroid potency as well as are poorly absorbed.The insoluble forms have better ocular bioavailability and are considered more potent anti-inflammatories for topical ocular use.
Characteristics:
i. An ophthalmic suspension should use the drug in a microfine form; usually 95% or more of the particles have a diameter of 10 µm or less.
ii. This is to ensure that the particles do not cause irritation of the sensitive ocular tissues & that a uniform dosage is delivered to the eye.
iii. An important development aspect of any suspension is the ability to resuspend easily any settled particles prior to instillation in the eye as well as ensure that a uniforn dose is delivered.
iv. The viscosity required to retard settling of the insoluble particles completely(should be viscous).
Disadvantage:
i. Controlling of particle size:As the drug particles are extremely small,as well as to rapid tear turnover rate they are washed out of eye relatively quickly.
ii. Potential problem associated to ophthalmic suspension is possibility of change in particle size during storage.Suspension products should have a “Do Not Freeze” warning on label because they are likely to agglomerate on freezing & will not resuspended by simple shaking.
iii. It would be ideal formulate a suspension that does not settle since the patient may not always follow this labeled instructions to shake well before using.
Improved beneficial suspension has been designed:
It may control the flocculation of insoluble active ingredient particles,such that they will remain substantially resuspended (95%) for many months & any settle particles can be easily to only a few seconds of gentle has well as shaking.
Many solution based formulations were tried but to limited success.
Resin bound form of beta blocker betaxolol formulated as suspension.
↓
Increase ocular bioavailability and improved ocular tolerance significantly.
M/A
It would appear sustained release of a active betaxolo occurs through exchange to cations such sodium and potassium in tear fluid resulting prolonged tear levels of drug and substantial increase in ocular bioavailability.
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