Pharmaceutic 3 Exam
Terms
undefined, object
copy deck
- how are opthalamic solution preserved?
-
1. Benzalkonium chloride, 0.013%
2. Benzethonium chloride, 0.01%
3. Chlorobutanol, 0.5%
4. Phenylmercuric acetate, 0.004%
5. Phenylmercuric nitrate, 0.004% and
6. Thimerosal, 0.01%.
Benzalkonium chloride is one of the most reliable ophthalmic solution preservatives, because it has a broad antimicrobial spectrum of activity, but the pharmacist must be aware of its incompatibility with anionic drugs. In some ophthalmic preparations, a mixture of benzalkonium chloride (0.01%) and EDTA (0.01 to 0.1%) is employed to remove the most resistant strains of Pseudomonas aeruginosa. EDTA is a chelating agent for metals which removes the metal from the surface of the organism and render the resistant Pseudomonas more sensitive to the benzalkonium chloride. - Why is isotonicity important in opthalamic solution prep?
-
Tears are isotonic with 0.9% NaCl. Ideally ophthalmic solutions should be made isotonic but eye can tolerate 0.5 - 2.0% NaCl solutions without a marked pain response. In compounding it is more important to consider the sterility, stability and preservative aspects of ophthalmics than to jeopardize these to attain precise isotonicity.
Therapeutic concentration of drug may be by itself be hypertonic, e.g., sodium sulfacetamide is used in 10-30% concentration, although a 3.5% concentration is isotonic but eye appears to tolerate hypertonic solutions in general, better than markedly hypotonic solutions probably because tears can dilute out hypertonic solutions to concentration closer to isotonicity. - Why is buffering used in Opthalamic preparation?
-
Buffers may be used in an ophthalmic solution for one or all of the following reasons: (1) to reduce discomfort to the patient, (2) to ensure drug stability, and (3) to control the therapeutic activity of the drug substance.
Many drugs used in the eye are chemically most stable at acid pH’s e.g., ph 5.0 (examples: atropine, homatropine, pilocarpine, physostigmine). Tears have pH ~ 7.4 and if acidic or alkaline solutions with significantly different pH’s and a high buffer capacity are placed in the eye, noticeable pain may occur which leads to lacrimation and flushing away of instilled drops. In consequence of this, many ophthalmics are prepared with weakly buffered systems so the drug will remain stable in-vitro but when drops are instilled, the moderate buffer capacity of tears is sufficient to maintain tear pH in physiologically comfortable eye.
Most drugs, including many used in ophthalmic solutions, are most active therapeutically at pH levels which favor the undissociated molecule. However, the pH that permits greatest activity may also be the pH at which the drug is least stable. For this reason, a compromise pH is generally selected for a solution and maintained by buffers to permit the greatest activity while maintaining stability. - Name the thre buffering systems.
-
1. Boric Acid Vehicle
2. Special Boric acid Vehicle
3. Isotonic Phosphate Vehicle - Defn Boric Acid Vehicle
-
1.9% w/v in water
 pH slightly below 5.0
 approximately isotonic
 very low buffer capacity since only “acid†is present
 without any boric acid “salt†- Defn Special Boric Acid Vehicle
- Same as above except it also contains 0.1% w/v sodium sulfite to act as an anti-oxidant to protect drugs as physostigmine and epinephrine which are easily oxidized in solution.
- What is an Isotonic Phosphate Vehicle?
-
This is the “Sorenson’s†phosphate buffer with added sodium chloride to make isotonic.
Isotonic Phosphate Vehicle – The phosphate buffer system adjusted for isotonicity provides a choice of pH from 5.9 to 8.0. This vehicle requires two stock solutions, one containing 8.00 gm of NaH2PO4 (monobasic sodium phosphate) per liter, and the other containing 9.47 gm of Na2HPO4 (dibasic sodium phosphate) per liter, the weight being on the anhydrous basis. The stock solutions are used in the proportions indicated in Table 1
If drugs are added to the above isotonic vehicle, the solution becomes hypertonic. This is satisfactory without correction, if the tonicity does not increase too much. If the hypertonicity produced is unacceptable it can be avoided by using the “sprowl’s method†of compounding, i.e., dissolve the drug in the volume of distilled water which will yield an isotonic solution from the drug alone, then q.s. to final volume with isotonic phosphate vehicle. The same technique can be used with Boric Acid vehicles.
Note: many ophthalmic drugs are large molecular weight compounds but are used in
low concentration, e.g., 1% or less. Consequently, the drug alone does not affect the
tonicity markedly, and, if added to an isotonic vehicle, will not produce
“physiologically intolerable†hypertonicity. Some pharmacists use 0.8% NaCl solutions
as a vehicle in which case the added drug (on an average) will raise the solute concentration
to isotonic levels. - Why is viscosity important in opthalamic preparations?
-
Because of continual tear production and flow across eye from lacrimal glands to drainage ducts into nasal passages, the “dwell time†of eye drops in eye is rather short
To increase “dwell time†in eye, ophthalmic solutions frequently include a viscosity-increasing agent. - What is the primary benefit of a viscous opthalamic prep?
-
i) increase ocular contact time.
ii) decrease drainage rate.
iii) increase drug bioavailability. - Secondary benefit?
- i) “lubricating†effect - a rather subjective benefit but noticed by many patients.
- What are some disadvantages of viscosity imparting agents?
- i) tendency to dry to a film on the eyelids. Can easily be removed by wiping with a damp tissue.
- What are the most important viscosity-imparting agents?
-
i) Polyvinyl Alcohol (PVA) - used in 1.4% concentration by Allergan Lab in “liquifilm†products.
ii) Cellulose derivatives, e.g.,
 methyl cellulose
 hydroxy propyl methylcellulose - used by Alcon labmost often as 0.5% solution. - What is the use of Surfactants in Opthalamic prep?
-
Surfactants are greatly restricted in ophthalmic solutions because of either irritation or toxicity to eye. The order of toxicity is: anionic> cationic> nonionic.
Several nonionic surfactants are used in relatively low concentration to aid in dispersing steroids in suspensions and to achieve improved solution clarity. For example, chloramphenicol is made into an ophthalmic solution using the following formula:
Polyoxyl 40 stearate 7%
PEG 300 15%
Chloramphenicol 0.55%
Water q.s. ad 100%
Solution is clear, stable and non-irritating. - What is the purpose of Opthalamic suspension?
- Ophthalmic suspensions are employed to a lesser extent than are ophthalmic solutions, however, suspensions may be used to increase the corneal contact time of a drug substance and thus provide a more sustained action. Ophthalmic suspensions may be required when the medicinal agent is insoluble in the desired vehicle or unstable in solution form.
- What are some properties the suspensions must have?
- Ophthalmic suspensions must possess the same characteristic of sterility as ophthalmic solutions, with proper consideration given also to preservation, isotonicity, buffering, viscosity and packaging. Additionally, ophthalmic suspension must contain particles of such chemical characteristics and small dimensions that they are non-irritating to the eyes. The ophthalmic suspension must also be of such a quality that the suspended particles do not agglomerate into larger ones upon storage. The suspension must be shaken prior to use and the particles distributed uniformly throughout the vehicle.
- What is the purpose of an opthalamic ointment and waht are some of it's properties?
-
Ophthalmic ointments must be sterile. They are either manufactured from sterilized ingredients and under rigid aseptic conditions, or they are sterilized following manufacture.
The ointment base selected for an ophthalmic ointment must be non-irritating to the eye and must permit the diffusion of the medicinal substance throughout the secretions. The bases must be melting or softening at body temperature. In most instances, mixtures of petrolatum and liquid petrolatum (mineral oil) are utilized as the ointment base. Sometimes a water-miscible agent as lanolin is added. This permits water and water-insoluble drugs to be retained within the delivery system.
The medicinal agent is added to the ointment base either as a solution or as a finely micronized powder. The drug is then intimately mixed with the base, usually by milling.
After preparation the ophthalmic ointments are filled into previously sterilized tin or plastic ophthalmic tubes. These tubes are typically small, holding approximately 3.5 g of ointment and fitted with narrow gauge tips which permit the extrusion of narrow bands of ointment. - What is the primary advantage of an opthalamic ointment over a opthalamic solution?
-
The primary advantage of an ophthalmic ointment over ophthalmic solution is the increased
ocular contact time of the drug. Studies have shown that the ocular contact time is two to four times
greater when ointments are used than when a saline solution is used. One disadvantage to
ophthalmic ointment use is the blurred vision which occurs as the ointment base melts and is spread
across the lens. - What are the two solid dosage forms?
-
1. ocuserts
2.Soft contact lenses - Defn Ocusert
-
 “Prolonged-release†dosage form
 introduced in about 1975
 places drugs between two membranes attached to a plastic ring
 the device is inserted under lower eyelid and left in place for 7 days. - What are soft contact lense made of?
-
 composed of various polymeric materials.
 have also been used as drug delivery systems with success.
 delivery rate is “first order, however, so an initial high rate of release decreases with time. - What is a pharmaceutical aerosol?
- Pharmaceutical aerosols are pressurized dosage forms containing one or more active ingredients which upon actuation emit a fine dispersion of liquid and/or solid materials in a gaseous medium. Aerosols are similar to other dosage forms in that they require the same types of considerations with respect to formulation, product stability, and therapeutic efficacy. However, they differ from most other dosage forms in their dependence upon the function of the container, its valve assembly, and an added component - the propellant - for the physical delivery of the medication in proper form.
- How does a pharmaceutical aerosol work?
- The term pressurized package is commonly used for aerosol product. Pressure is applied to the aerosol system through the use of one or more liquefied or gaseous propellants. Upon activation of the valve assembly of the aerosol, it is the pressure exerted by the propellant which forces the contents of the package out through the opening of the valve.
- What is a pharmaceutical Aerosol used for?
-
Aerosols used to provide an airborne mist are termed space sprays. Room disinfectants, room deodorizers, and space insecticides characterize this group of aerosols. The particle size of the released product is generally quite small, usually below 50 μm.
Aerosols intended to carry the active ingredient to a surface are termed surface sprays or surface coatings. The dermatological aerosols can be placed in this group. Also included are a great many non pharmaceutical aerosol products, as personal deodorant sprays, cosmetic hair lacquers and sprays, perfume and cologne sprays, shaving lathers, toothpaste, surface pesticide sprays, paint sprays and various household products such as spray starch, waxes, polishes, cleaners and lubricants. A number of veterinary and pet products have been put into aerosol form as have been such food products as dessert toppings and food spreads. Some of these products are sprays; others, foams; and a few, paste-like products. - What are Advantages of Aerosol Dosage Form?
-
1. Convenience of use.
2. Sterile use is possible - a dose can be removed without contamination of the remaining materials.
3. Chemical stability of its content is improved - content is protected from the atmosphere (e.g., oxygen/moisture/light)
4. The medication can be delivered to the affected area in a desired form such as spray, stream, quick-breaking foam or stable foam.
5. Irritation produced by the mechanical application of topical medication is reduced or eliminated.
6. Application of medication in a thin layer - less wastage of drugs
7. Drugs can be delivered directly to the respiratory system.
8. Expensive drugs can be economically applied by suitable metering valves.
9. Aerosol application is a “clean process, requiring little or no “wash-up†by the user. - What are Disadvantages of Aerosol Dosage Form?
-
1. Cost of manufacturing and packaging
2. Inconvenience – may be too bulky to carry around .
3. Limitation of present aerosol technology:
a) only about 10 to 20% of drug can reach the target region of the respiratory system.
b) users’ complaints: - Clogging
Loss of spraying power
Product left in can.
4) potential toxicity or adverse reactions from propellent - Describe a liquefied gas system
-
part of propellant is present as liquid and part as vapor in equilibrium with liquid.
produces more constant power than compressed gas systems. - Two Phase System (solution)
-
 the two phase aerosol system is comprised of the liquid phase, containing the liquefied propellant and product concentrate, and the vapor phase.
 examples:
a) space spray:
 very fine “particles†produced
 use large concentration of propellant
 e.g. insecticides, room deodorant
b) surface-coating spray (wet or coarse spray)
 large “particles†produced
 use smaller amount of propellant
 e.g. hair spray, perfumes, topical spray, protective coating. - What is the two layer system?
- A type of Three phase systemThis system is comprised of a layer of water-immiscible liquid propellant, a layer of highly aqueous product concentrate, and the vapor phase. Because the liquefied propellant usually has a greater density than the aqueous layer, it generally resides at the bottom of the container with the aqueous phase floating above it. To avoid expulsion of the reservoir of liquefied propellant, the dip tube must extend only within the aqueous phase (product concentrate) and not down into the layer of liquefied propellant.
- Define a Foam System
-
a three phase system
a liquefied propellant is emulsified as the internal phase of an o/w emulsion with the aqueous solution the second phase and the vapor phase (propellant) the third phase.
examples: shave cream, topical pharmaceuticals, contraceptives. - What are some characteristics of a Compressed Gas system?
-
 the gas is compressed in the container and it is the expansion of the compressed gas which provide the push or the force necessary to expel the contents from the container.
 as the content of the container is exhausted, the volume of gas will increase causing a drop in pressure according to Boyle’s law, PV = constant
 gases commonly used are nitrogen, carbon dioxide and nitrous oxide.
 An advantage of nitrogen as a propellant is its inert behavior toward other formulative components and its protective influence to oxidation. Further nitrogen is odorless and tasteless gas and thus does not contribute adversely to the smell or taste of a product.
 they have pressures in excess of 700 psig at 70oF when liquefied.
 e.g. carbon dioxide, nitrous oxide
 less used in aerosol than fluorocarbon and hydrocarbon
 odorless
 tasteless
 low in toxicity
 inexpensive - 3 Disadvantages of Compressed Gas
-
a) expelling pressure decreases with use.
b) when container is accidentally inverted, the vapor phase is discharged
c) wet spray (coarse particles) - What are types of compressed Gas system?
-
Solid Stream Dispensing "
the concentrate (dispensed product) is semisolid
very high pressure is used, 90-100 psig at 70oF.
examples: dental creams, hair dressing, food product"
"Foam dispensing
" "
the gas is dissolved in the concentrate which expands on exiting from the aerosol to form foam.
gases used are nitrous oxide, carbon dioxide
" - Name some miscellaneous systems
-
Piston Type-
the product is generally semisolid. It is fitted with a piston and propellant. When the valve is opened, the pressure against the piston pushes the piston, causing the product to be dispensed.
examples: cheese spread, cake decorating icings and ointments
Plastic Bag Type- a collapsible plastic bag which contains the dispensed product is fitted into a container and the propellant is introduced at the bottom of the container.
the concentrate (dispensed product) used can be semisolid or liquid
It is an attempt to separate the product from the propellant. - Name the components of an Aerosol product
-
1) Concentrate
2) Propellent
3) Container
4) Valve and Actuator - What is the product concentration of an Aerosol product?
- The product concentrate is the active ingredient of the aerosol combined with the required adjuncts, such as antioxidants, surface-active agents, and solvents, to prepare a stable and efficacious product e.g., suspension, emulsion, solution, semisolid or powder.