Ophthalmic 2012

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    ObjectivesStudents will be able to discuss: Definition of Eye drops Factors to concern for the preparation of

    eye drops

    The component of eye drop formulation Preparation of eye drops.

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    Definition

    Ophthalmic preparations are sterile, liquid, semi-solid or solid preparations intended foradministration upon the eyeball and/or to theconjunctiva or to be inserted in the conjunctival sac.

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    Types of ophthalmic preparations

    Several categories of eye preparations may bedistinguished:

    1) Eye drops.2) Eye lotions.3) Semi-solid eye preparations.

    4) Ophthalmic inserts.

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    Depending on the condition being

    treated, they may contain :

    Steroids (e.g dexamethasone ), Antihistamines Sympathomimetics Beta receptor blockers

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    parasympathomimetics (e.g

    pilocarpine .), parasympatholytics (e.g. atropine ), prostaglandins , non-steroidal anti-inflammatory drugs

    (NSAIDs) or topical anesthetics .

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    Eye drops sometimes do not have

    medications in them and are onlylubricating and tear-replacing solutions

    and they can also contain anti-rednessand similar chemicals.

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    Extemporaneous preparation of eye drops involvesthe following:

    I. Preparation of the solution.

    II. Clarification.III. Filling and sterilization.

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    Factors to be considered in theformulation of ophthalmic preparations

    includes 1. pH

    2. Isotonicity3. Viscosity

    4. Sterilization5. Preservation

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    Preparation of the solution

    1.Active ingredient(s) to produce desiredtherapeutic effect.

    2.Vehicle , usually aqueous but occasionally may beoil.

    3.Antimicrobial preservative to eliminate any

    microbial contamination during use and thusmaintain sterile.

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    4. Adjuvants to adjust tonicity , viscosity or pH in order to increase the comfort

    in use and to increase the stability of the active ingredient(s).

    5. Suitable containers for administrationof eye drop which maintains the

    preparation in a stable form and protectsfrom contamination during preparation,storage and use.

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    Excipients used

    1. viscosity inhancers : Increasing the viscosity of an eye drop increases the

    residence time of the drop in the eye and results in

    increased penetration and therapeutic action of thedrug.

    The common agents and their maximumconcentration used in ophthalmic formulations arein the below:

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    Viscosity Enhancers:

    Hydroxy ethyl cellulose Hydroxy propyl methyl cellulose Methyl cellulose

    Polyvinyl alcohol

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    . Buffers1 They are compounds that resist changes in pH upon

    the addition of limited amounts of acids or bases.

    Buffer systems are usually composed of a weak acidor weak base and its conjugate salts.

    Examples:Borate buffer.Phosphate buffer.

    Citrate buffer .

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    Solution pH : The physiologic pH of tears is

    approximately 7.4 . Thus, this would bethe optimal pH of ophthalmic solutions

    for eye comfort.

    Ophthalmic solutions may range frompH 4.5 - 11.5. But the useful range toprevent corneal damage is 6.5 to 8.5.

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    The components act in such a way that

    addition of an acid or base results in theformulation of a salt causing only a smallchange in pH.

    Buffer capacity is a measure of theefficiency of a buffer in resistingchanges in pH.

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    Antioxidant :

    Sodium bisulfite

    Sodium meta bisulfite Thiourea

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    Preservatives should be used that do notcause patient sensitivity or that are

    incompatible with the other ingredients in theformulation.

    This is to ensure that the eye drops aremaintained sterile during use and will notintroduce contamination into the eyes being

    treated.

    exampel: Benzalkonium chloride

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    Preparation procedure

    It involves the following procedure :

    Preparation of the solution. Clarification Filling and sterilization

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    Preparation of the solution

    The aqueous eye drop vehicle containing anynecessary preservative, antioxidant, stabilizer,tonicity modifier, viscolizer or buffer should beprepared first.

    Then the active ingredient is added and thevehicle made up to volume.

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    The clarified solution is either:

    1. Filled directly into the final containers whichare sealed prior to heat sterilization.

    or

    2. Filled into suitable container prior to filtration

    sterilization.

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    Osmotic and PH

    pH control importance:

    1. The pH offering the best stability during

    preparation and storage.2. Offering the best therapeutic activity.3. The comfort of the patient.4. The lacrimal fluid has a pH of 7.2-7.4, so

    when possible eye drops should be bufferedto reduce stinging on instillation

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    A 0 9% solution of NaCl (Normal Saline) is iso

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    A 0.9% solution of NaCl (Normal Saline) is iso-osmotic with blood and tears.

    isotonic or iso-osmotic solutions do not damagetissue or produce pain when administered.

    Solutions which contain fewer particles and exert alower osmotic pressure than 0.9% saline are calledhypotonic

    Administration of a hypotonic solution producespainful swelling of tissues as water passes from theadministration site into the tissues or blood cells.

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    :Hypotonic

    Water enters cell.Cell swells and bursts.

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    Solutions which contain particles and

    exert higher osmotic pressures arereferred to as hypertonic .

    Hypertonic solutions produce shrinking of tissues as water is pulled from thebiological cells in an attempt to dilute thehypertonic solution.

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    Hypertonic:

    Water exit cell.

    Cell shrinks dueto water loss.

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    Objectives

    Sample calculationContainers & packaging

    Contact lens productsEye & ear drops

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    Sample calculation:Calculate the amount of NaCl required to make the

    following ophthalmic solution isotonic.

    Oxytetracyline HCl 0.5%Sodium Chloride Q.S.Purified water add30mlMake isotonic solution

    E = 0.12

    Determine the amount of NaCl to make 30 ml of an

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    Determine the amount of NaCl to make 30 ml of anisotonic solution

    0.9 g 100 mlX 30ml

    X = 0.27 g Nacl ---------------------

    2 Calculate the contribution of

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    2- Calculate the contribution of Oxytetracyline HCl to the NaCl equivalent

    30 ml 0.5 g/100 ml = 0.15 g Oxytetracyline HClE of Oxy tetHcl = 0.12 Nacl

    1 g 0.12 g NaCl0.15 g ?

    0.15 g x 0.12 / 1 = 0.018 g NaCl --------------------

    5% oxytet. HCl5100 ml

    ? 30 ml

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    3. Determine the amount of NaCl to add tomake the solution isotonic by subtracting

    from

    0.27 g - 0.018 g = 0.252 g.

    P bl i t i l ti l l ti

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    Problem on isotonic solutions calculationsusing the NaCl E-value:

    How many grams of NaCl should be used incompounding the following prescription?

    Pilocarpine nitrate 0.3 gSod. Chloride Q.S.

    Purified water add 30 ml

    Make isotonic solution.

    E =0.23

    I Normal saline 0.9% means :

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    I Normal saline 0.9% means :0.9 g ---------------------- 100 ml

    X g ---------------------- 30 mlX = 0.9 x 30 / 100 = 0.27 g

    II E = 0.23 Means :1 g Pilocarpine nitrate = 0.23 g NaCl

    0.3 g -------------------------- Y NaClY = 0.3 g x 0.23 / 1 = 0.069 g

    III Q.S. means :o.27 0.069 = o.2 g

    C t i d k i

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