الجمعة، 12 يونيو 2009

كل ما يمكن عن التركيبات

INTRODUCTION OF ORAL LIQUID DOSAGE FORMS
:


- why pharmacist should compound oral dosage forms?




1 - Many drug products are not commercially available as oral liquid

.

مثال: عند نقص دواءالـ Buscopan syrup من السوق كان لابد من ايجاد طريقة اخرى لتحضيرة فى هيئة سائل من اجل الاطفال



2- Infants, pediatric, and some psychiatric patients cannot swallow solid dosage forms. 3- Drugs are often more bioavailable in liquid form than solid form

.

*difficulties facing pharmacist who is going to prepare an oral liquid dosage forms:


- unstable drugs are even more unstable in solution. - Poorly soluble drugs must be solublised or suspended. - Bad tasting drugs must be flavored to be relatively platable. - Multiple dose packages need a proper preservation system
.

ودى من المشاكل اللى بتواجهنا واحنا بنحضر السوائل لذلك فى احتياطات يجب اتخاذها لتقليل هذة المشاكل وتفاديها وتحسين خواص التركيبة ومنها:



1- The source of active ingredients:
the pharmaceutical or analytical grade chemicals are better for use rather than ones derived from commercially available drug like injection, tablets, or capsules
.

يجب تحرى الدقة فى المصدر اللى بنحصل منة على المواد الخام لانها بتكون افضل من اللى بنحصل عليها من الحقن او الاقراص والكبسولات.



2- Sustained acting or slow release tablets or capsules are not suitable for use as a source of the active ingredients.
لايصح استعمال الاقراص اوالكبسولات ممتدة المفعول او بطيئة المفعول فى تحضيرالسوائل


3- Physicochemical properties of the active ingradients, pH of maximum stability and solubility may be greatly influence the quality and the activity of pharmaceutical dosage form
.

* PH is critical in maintaining drug in solution, a slight inc. or dec. in the pH
can cause some drugs to precipitate from a solution
.
-a slight adjustment of PH can aid in solubilising some drugs.

N.B: Basic drugs are highly soluble in acidic medium and vice versa
.


Stability and storage condition of preparation
:

N.B:-liquids for oral use may contain suitable antimicrobial preservative, antioxidants, and other exepients such as dispersing, suspending, thickening, emulsifying, buffering, wetting, solubilising, flavoring, sweetening and coloring agents.
والمواد المضافة دى هدفها هى تحسين خواص السائل للوصول الى الشكل المرغوب فية من حيث الخواص والطعم والشكل .......الخ.


- Storage Oral liquids should be stored in well closed containers.
Labeling :
the label should states
:

1- The date after which the oral liquid is not intended to be used
.

يجب ان ندون تاريخ الصلاحية.
2- The conditions under which the oral liquid should be stored.
شروط التخزين للدواء مثل درجة الحرارة....الخ



3- For oral emulsions, oral suspensions……etc
the bottle should be shaken before use






التوقيع :
رد باقتباس
قديم 05-03-2008, 05:05 PM #2
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Post 2-Suspension

Suspensions




Definition


عندما تكون المادة الفعالة غير ذوابة في الماء .. عندها يمكن وصف أحد هذين الشكلين : المعلق (suspension)او المستحلب (emulsion)



و المعلق بشكل عام مؤلف من طورين : (two phases)الطور الاول صلب(بودرة ناعمة) مبعثرة في الطور الثاني و هو طور اما صلب او سائل او غاز.



يكون المعلق شكل صيدلاني مناسب عندما تكون المادة الفعالة غير ذوابة في المادة المحلة التي تسمى هنا (vehicle) .


المعلق الجيد تكون فيه المادة الفعالة موزعة بشكل متجانس في المادة الحاملة (vehicle) المعلقات المعدة للتعاطي بطريق الفم ( orally suspensions) تكون عبارة عن مادة فعالة مبعثرة في محلول محلـّى و منكـّه.(sweetened & flavored) و لزج نسبياً.



المعلقات الموضعية (topical suspensions) تكون فيه المادة الفعالة مبعثرة في سائل مناسب للجلد .. و أحياناً تسمى هذه المستحضرات بالـ(lotions) مثل (calamine lotion).



Applications:
ان المادة الحاملة (vehicle) الواجب استخدامها يجب ان تكون ذات لزوجة كافية لتعليق الاجزاء الصلبة و الحفاظ عليها منفصلة .. و بالمقابل يجب ان تكون سائلة الى حد يسمح للمعلق بالانسكاب من الزجاجة ..


يمكن ان يشمل هذا الشكل الصيدلاني ( المعلق) مستحضرات عينية – اذنية و انفية ايضاً بالاضافة للمستحضرات الموضعية و الداخلية .



هذا الشكل الصيدلاني يمكن ان يعزز ثباتية المواد الفعالة التي غالبا ما تكون قليلة الثبات في المحاليل.



Composition:


Suspensions usually contain insoluble particles, a liquid medium, a suspending agent/ surfactant/ viscosity enhancer, and a preservative. They can also contain a flavoring/perfume agent and a sweetener
.

The order in which these ingredients are blended is important to the stability of the preparation


.

Preparation

:

لتحضير المعلق يجب على الصيدلي بالبداية أن يحضر مسحوق ناعم متجانس من المادة الفعالة و ذلك بسحق المادة و تمريرها عبر منخل ناعم .. بعد ذلك يجب تبليل المادة الغير منحلة بشكل تام قبل مزجها بالسائل الحامل( vehicle.)



Hydrophilic materials are best wetted with water-miscible liquids (e.g.: glycerin), whereas hydrophobic substances can be wetted with nonpolar liquids or with the use of a surfactant

.

The general guideline is to use the minimal amount of wetting agent required to produce the desired product


.

After the drug and wetting agent have been combined to form a thick paste the vehicle can be added with constant stirring. Methylcellulose preparations are best prepared by dispersing the polymer in about one third to one half of the total volume of hot water, followed by adding the remaining water as ice water or ice


.

Many polymers can be sprinkled onto rapidly agitating water to improve their dispersion



.


Physicochemical considerations

:

Sample suspension vehicles are listed in the following table:

Suspending agent == (%)Final concentration
Acacia======================== = 2-5
Carbomer resins================== 0.5-5
Carboxymethylcellulose sodium ====== 0.5-1.5
Colloidal silicon dioxide ============1.5-3.5
Methylcellulose ================== 0.5-5
Tragacanth ===================== 0.5-2
Vehicle ================== Ph
Ora-plus ====================== 4-4.5
Suspendol-s ====================5.3-6





في حال تعذر الحصول على (suspension vehicle) جيد .. عندها يمكن تحضير محلول ميتيل سيللوز (0.5-5%) ..أو محلول كاربوكسي ميتيل سيللوز الصوديوم (0.5-1.5%)

ان اللزوجة المطلوبة تعتمد على استقرار المادة الفعالة في المعلق و الذي بدوره مرتبط بكثافة بودرة المادة الفعالة من جهة و أبعاد أجزائها من جهة ثانية.


The following table provides a list of the conc. Of the viscosity-increasing agents that will yield a viscosity of 800 centipoise (cp):

Viscosity agent======== (%) Concentration required
Acacia ============================== ===== 35
Bentonite===================== ============ 6.3
Carboxymethylcellulose , low ====================4.1
Carboxymethylcellulose , medium =================1.9
Carboxymethylcellulose , high ===================0.7
Methylcellulose 100cp ========================3.5
Methylcellulose 400cp ========================2.4
Methylcellulose 1500cp =======================1.7
Tragacanth ============================== =2.8
Veegum======================== ========== 6


After the suspending agent is prepared, it can be mixed 1:1 with a flavored syrup



.


Viscosity and rheology


:

تلعب اللزوجة دور هام في كثير من الاشكال الصيدلانية .
  • فهي ضرورية لإبقاء المادة الفعالة معلقة في المعلق(suspension)
  • تعزز ثبات المستحلبات (emulsions)
  • تغير من معدل تحرر المادة الفعالة في مناطق التطبيق..( Altering the release rate of drugs at sites of application)
  • و تجعل تطبيق الدواء أسهل في مناطق عديدة من الجسم .. حيث تمنعه من السيلان ..

Preparation methods

:


أفضل مزج لمعظم رافعات اللزوجة يكون بأحد الطرق التالية :


  • بسكب البودرة ببطء و استمرار على الماء الذي نقوم بتحريكه بقوة مع استمرار التحريك أثناء السكب..و اثناء التميه (hydration).
  • الطريقة الثانية تكون بمزج البودرة مع مادة اخرى منحلة بالماء كالسكر (sucrose) قبل الاضافة الى الماء.
  • الطريقة الثالثة تكون بعمل معجون (Paste) مع سائل ممتزج مع الماء مثل الغليسرين قبل الاضافة للماء.
يفضل عند بعض رافعات اللزوجة ان تضاف مبدئياً على الماء الحار .. و بعد ذلك يضاف ما تبقى من الماء البارد.

هذه الطرق تساعد على الاقلال من حدوث التجبل (clumping) الذي يمكن ان يحدث مع مثل هذه البوليميرات (polymers) و الذي يجعل من عملية التحضير أمراً صعباً .

احد اهم خصائص المعلق الجيد .. امكانية اعادة التعليق (resuspendability) .
يجب على الصيدلي عند تحضير المعلقات ان يتأكد أن المستحضر ليس سميكاً(thick) جداً..لأنه عندها سيكون من الصعب سكبه و خاصة ان وضع في الثلاجة.





Quality control

:


تضم عملية مراقبة الجودة ما يلي:
  • الوزن/الحجم
  • الثبات المديد (extend settling)
  • سهولة إعادة البعثرة (dispersibility)
  • المظهر
  • الرائحة
  • قابلية السكب

و يجب تدوين هذه المعلومات و ان امكن فحصها بشكل دوري.

يمكن تحديد مدى استقرار المعلق بتركه على الرف يوم كامل و بعدها قياس ارتفاع الأجزاء المعلقة ... و عمل مقارنات مع التحضيرات الأخرى لنفس التركيبة .





Packaging/storage/labeling:

يجب تعبئة المعلق في أوعية محكمة الاغلاق .. و ذات فتحة كافية لسكب المعلق.. و أن يترك في العبوة بعض الهواء الكافي لإعادة رج العبوة ..

تحفظ في حرارة الغرفة او في الثلاجة و ذلك حسب خصائص المادة الفعالة .

على اللصاقة (label) يجب توضيح ضرورة رج الزجاجة قبل الاستعمال.. و توضيح ان كان المستحضر معد للاستعمال الداخلي ام الخارجي..





Stability:

يجب مراقبة التغيرات الفيزيائية التالية :



التجانس – الاستقرار – نمو الكريستالات - صعوبة اعادة البعثرة - نمو العفن و الباكتيريا - الرائحة – نقص الحجم.


المعلق اقل عرضة للتفكك و التحلل الكيميائي(degradation) من المحاليل.. و لكن بوجود الماء فإن فترة الصلاحية تكون قصيرة نسبياً .
المعلقات الحاوية على الماء لا تملك فترة صلاحية اكثر من 14 يوم بعد التحضير ..عند وضعها بدرجة حرارة منخفضة .. و عندما يكون التحضير بدءاً من مواد صلبة ..

الصلاحية يمكن ان تكون اطول في حال توفر معطيات علمية عن ثباتية أطول للمعلق.







رد باقتباس
قديم 05-03-2008, 05:08 PM #3
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Post Syrup-2

How to formulate a syrup

?

First: what is the syrup
?


Definition:

-syrups are concentrated aqueous preparation of sugar or sugar-substitute with or without flavoring agent and medicinal substance.
او زى مابنسمية بالعربى الشربات.



Imp notes of syrups:

1-syrup is suitable if the drug is water soluble.

يجب ان تكون مادة التركيبة تذوب فى الماء.




2-it can mask unpleasant tasting of wide range of drugs.
ودا مهم جدا لان بعض الادوية بيكون طعمها غير مستساغ. فالسيرب بيحسن من طعمها وبالتالى من تقبلها لدى المرضى وخاصة الاطفال.




3-the viscosity of syrup will keep flavor in the mouth longer.




*problems of syrups:

-high sugar ******* of syrup is not suitable for diabetic
.

-it decreases dissolution rate and extent of active ingredients.


-its high viscosity will trap air bubbles for a longer period upon shaking or agitation of the preparation

.

N.B:
The preservative property of the syrup depends on the maintaining a high sucrose concentration in the final preparation.

- If sucrose conc. Decreased, it may be necessary to add another preservative
.

*one gram of sucrose preserves 0.53 ml of water and occupies 0.647 ml.
For ex
:

RX
Drug 1……… 120mg
Drug 2……… 20 ml
Water………..20 ml
Syrup Qs …...100ml
(Syrup contains 85% w/v sucrose according to USP
)

- this formula contain 60 ml syrup and this will contain (85%*60 ml)……..51gm


That means that 51 gm of sucrose in this formula will occupy (51*0.647)……..33 ml of solution & preserve (51*0.53)………27ml water


And this means that only 60 ml of formula is preserved.
So, to preserve the remaining 40 ml we need for example.
(0.1%*40) 0.04 gm Sorbic Acid
.

امثلة لبعض المواد الحافظة


Preservative .........concentration
Benzoic acid ...............0.2%
sodium benzoate .........0.2%
Methyl paraben .......=<>
propyl paraben........ =<>
Potassium sorbate ........0.2%
Sorbic acid................... 0.2%

N.B:
Most syrups have an acidic PH ranging between 3-7
.

Procedure of preparing syr is expressed in the following picture








رد باقتباس
قديم 05-03-2008, 05:09 PM #4
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Post Syrup-1

How to formulate a syrup


?

First: what is the syrup
?


Definition:

-syrups are concentrated aqueous preparation of sugar or sugar-substitute with or without flavoring agent and medicinal substance.
او زى مابنسمية بالعربى الشربات.


Imp notes of syrups:

1-syrup is suitable if the drug is water soluble.
يجب ان تكون مادة التركيبة تذوب فى الماء.




2-it can mask unpleasant tasting of wide range of drugs.
ودا مهم جدا لان بعض الادوية بيكون طعمها غير مستساغ. فالسيرب بيحسن من طعمها وبالتالى من تقبلها لدى المرضى وخاصة الاطفال.




3-the viscosity of syrup will keep flavor in the mouth longer.




*problems of syrups:
-high sugar ******* of syrup is not suitable for diabetic
.

-it decreases dissolution rate and extent of active ingredients.


-its high viscosity will trap air bubbles for a longer period upon shaking or agitation of the preparation

.
N.B:
The preservative property of the syrup depends on the maintaining a high sucrose concentration in the final preparation.
- If sucrose conc. Decreased, it may be necessary to add another preservative
.
*one gram of sucrose preserves 0.53 ml of water and occupies 0.647 ml.
For ex
:
RX
Drug 1……… 120mg
Drug 2……… 20 ml
Water………..20 ml
Syrup Qs …...100ml
(Syrup contains 85% w/v sucrose according to USP
)
- this formula contain 60 ml syrup and this will contain (85%*60 ml)……..51gm


That means that 51 gm of sucrose in this formula will occupy (51*0.647)……..33 ml of solution & preserve (51*0.53)………27ml water


And this means that only 60 ml of formula is preserved.
So, to preserve the remaining 40 ml we need for example.
(0.1%*40) 0.04 gm Sorbic Acid
.
امثلة لبعض المواد الحافظة


Preservative .........concentration
Benzoic acid ...............0.2%
sodium benzoate .........0.2%
Methyl paraben .......=<>
propyl paraben........ =<>
Potassium sorbate ........0.2%
Sorbic acid................... 0.2%
N.B:
Most syrups have an acidic PH ranging between 3-7
.
Procedure of preparing syr is expressed in the following picture







رد باقتباس
قديم 05-03-2008, 05:10 PM #5
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Post 3-Emulsion

Emulsions

Definitions / types

Emulsions are heterogeneous systems consisting of two immiscible liquids,one of which (the disperse phase) is finely divided and distributed through the other (the continous phase),since this type of dispersion is unstable .an emulsifying agent is usually required to maintain the dispersion


و يعرف المستحلب أيضاً بأنه مزيج غير ثابت من سائلين غير ممتزجين و عامل استحلابي (emulsifying agent).
عملية دمج مكونات المستحلب تسمى بالاستحلاب (emulsification ).


Emulsion consists of:


Dispersed phase (internal or discontinuous phase)

Dispersion medium (external phase or continuous phase)

Emulsifying agent



قطر كريات السائل المبعثر (dispersed phase ) عموما يتراوح بين 0.1-10 ميكرون.
و مع ذلك يمكن أن نجد مستحلبات فيها قطر الكريات 0.01 أو 100 ميكرون .


يمكن اللجوء لعمل المستحلب عندما يتوجب علينا جمع سائلين غير ممتزجين في مستحضر واحد.. أحدهما قطبي (polar) و الثاني غير قطبي (nonpolar).


يصنف المستحلب إلى مجموعتين o/w و w/o:

When the continous phase is aqueous the system described as oil-in-water(o/w) emulsion

And when the continous phase is oily the system described as water-in-oil(w/o) emulsion

المستحلب المعد للاستخدام الداخلي( internal use ) يكون من نمط (o/w)
و المستحلب المعد للاستخدام الخارجي(external use) يمكن أن يكون بأحد الشكلين.



Creams are opaque, soft solids or thick liquids consist of medications that are dissolved or suspended in water removable (i.e., vanishing cream) or emollient bases
.


و الكريمات معدة للاستعمال الخارجي و يمكن أن تكون من احد النمطين المذكورين.
الكريمات تستخدم عادة في حالات الإصابات الرطبة (weeping lesions) ذلك أن للكريمات أثر مجفف نوعاً ما و يمتزج مع السوائل الخارجة من الإصابة.


Lotions are fluid emulsions or suspensions designed for external applications.

They have a lubricating effect and thus are applied to intertiginous areas, that is, areas

where the skin rubs together, such as between the fingers, between the thighs, or under the arms.

Applications:


-Topical creams or lotions are popular forms of emulsions for external use,
-Internally, emulsions are used to dispense oil and aqueous drugs together, to mask the taste of unpleasant oily drugs, and sometimes to enhance the absorption of selected drugs.

-intravenously administered lipid emulsion used to administer high calories to severly debilitated patients.

]Composition
Emulsions generally contain three components:

A lipid phase

An aqueous phase

An emulsifier

The compounding pharmacist has the greatest flexibility in the choice of an emulsifier. Common emulsifiers are listed as the following :

Emulsifiers and stabilizers for use in emulsions:

Carbohydrates:

Acacia , Agar , Chondrus , Pectin , Tragacanth.

Proteins:

Casein , Egg yolk , Gelatin.

High molecular weight alcohols:

Cetyl alcohol , Glyceryl monostearate , Stearyl alcohol.

Surfactants:

Anionic , Cationic , Nonionic.

Solids:

Aluminum hydroxide , Bentonite , Magnesium hydroxide







to be continued
.







رد باقتباس
قديم 05-03-2008, 05:12 PM #6
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Post رد: تعلم معنا..التركيبات خطوة خطوة

Emulsion preparation:




emulsification is an energy consuming process,this energy can

be brought either by mechanicalor manual agitation,ultrasonic

vibration or heat
.



the commonly used techniques in emulsion preparation are morter and pestle,electric mixer,hand homogenizer and beakers


*
two main methods for manual emulsion preparation using morter and pestle are:



1-English method(wet gum method):

the ratio of oil,water and emulsifier is 41 respectively for primary emulsion .
the water and emulsifier is put into a rough surface morter,then the oil is added in small quantities with rapid trituration until the primary emulsion formed, additional water can be added slowly with trituration.




2-continental method(dry gum method):

the same ratio as before.the emulsifier is mixed with the oil,then the water is added in one time wih very rapid tritiuration until the emulsion is formed,additional water can be added slowly with trituration.



the beaker method :


it is often used for creames and lotions:


1-the ingradients are divided into two parts ,the oil with oil soluble
ingradients,and the water with water soluble ingradients


2-each phase is heated seperately to about 60-70 c,then the internal phase is added to the other phase with stirring


3- the product is allowed to cool gradually while stirring until the emulsion is formed and cooled.


Emulsifying agents:

The emulsifiers is intended to minimize the tendency of globules to coalesce together to form a large globules,the stability of an emulsion is dependant on the properties of rhe emulsifier.


Emulsifying agents may be-

Surface active agents(surfactants),hydrophilic colloids,or finely divided solid particles.
All r working at the oil-water interface resulting finally in formation of amicrofilm surrounding the oil globule resulting in its dispersion

HYDROPHIL-LIPOPHIL BALANCE(HLB):

HLB is a describing scale system of the surfactants-

-each surfactanthas HLB value which is determined
experimentally,this value indicates the relative number of hydrophilic groups to the lipophilic ones in the surfactant molecule.

-the higher the HLB value,the larger number of hydrophilic groups and hence the more hydrophilic properties of the surfactant.

HLB value:

antifoaming agents 1-3

emulsifying agents(w/o emulsion) 3-6

wetting agents 7-9

emulsifying agents(o/w emulsion) 8-18

detergents 13-16

solubilizing agent 16-18







رد باقتباس
قديم 05-03-2008, 05:15 PM #7
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Post

BLENDING OF SURFACTANTS
:

غالبا مايكون استخدام اكثر من عامل استحلابى بينتج عنة مستحلب اكثر ثباتا


-

because the HLB numbers are additive,the HLB value of ablend can be readily calculated


ومن الممكن جمع اكثر من عامل استحلابى عن طريق النسبة والتناسب


for example:


if 20ml of an agent with an HLB value of 9.65 is required ?


then two surfactants one with HLB value of 8.6

and one with HLB value of 12.8, can be blended in 3:1 ratio& the following quantities of each surfactant will be required

3\4 * 8.6 = 6.45(15ml)

1\4 * 12.8 =3.20(5 ml)

total HLB = 9.65(20ml)
to calculate the HLB required for the emulsifier in the formulation below, the following method is used:




petrolatum ..... 25g .... 56(25g\45g) *.... 8 = 4.5(portion of HLB)

cetyl alc. ..... 20g .... 44(20G\45G) *..... 15 = 6.7(portion of HLB)


N.B ( 56 & 44 r the % of oil phase and 8 & 15 r the required HLB).

emulsifier ..... 2g .

preservative ..... 0.2g .

pure water qs ad .... 100g .

Approximate HLB value for emulsifier = 4.5+ 6.7=11.2

PRESERVING AN EMULSION
:

-
المستحلب من السهل ان يكون وسط لنمو البكتريا, وهذا من السهل حدوثة اما اثناء التحضير او اثناء الاستخدامز وبالتالى فمن الافضل ان يكون مكان التحضير والادوات المستخدمة يجب ان تكون نظيفة وغير ملوثة

وبالرغم من ذلك فاذا كان المستحلب سيتم الاحتفاظ بة لفترة طويلة فعلينا استخدام مادة حافظةزوالتى يجب ان تتمتع ببعض الخواص:


-It must be non-toxic,stable.compatible and inexpensive,,in addition :it must have an acceptable taste .odor and color

it also should be effective against a wide variety of bacteria,fungi and yeasts




-المادة الحافظة يجب ان تكون مركزة فى الوسط المائى للمستحلب(aqueous phase) لان النمو الطبيعى للبكتريا يكون فى هذا الوسط



-

because of nonionized form of the preservative is more effective against bacteria than the ionized form,so most of the preservative should be in the nonionized state


*to be effective,the preservative must be neither bound nor absorbed to any agent in the emulsion or the container
.

***the parabens(methyl paraben ,propyl paraben,butyl paraben) are considered to be some of the most satisfactory preservatives for emulsions
.
OILS AND FATS can become rancid,which causes the product to have an unpleasant odor,appearance and taste.antioxidants can prevent rancidity

examples of antioxidants used in emulsion:

-ascorbic acid

-ascorbyl palmitate







رد باقتباس
قديم 05-03-2008, 05:17 PM #8
clinical pharma
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FLAVORING AN EMULSION:



-when selecting an appropriate flavoring agent,the pharmacist should take into consideration the dispersion medium(external phase) of the emulsion

*
for example: If a flavoring oil is used and most of the oil partitions into the internal phase as an oil in water emulsion,the flavor will be reduced in strength -oils can be incorporated by using small quantities of surfactants(usually surfactants with HLB value of 15 to 18 are used)…often in conjunction with asurfactant with HLB value in the range 8 to 12






**As a general Rule::

-it is necessary to have from 3 to 5 times as much surfactant as oil(flavoring) to ensure solubilization



-for best results:the oil should be mixed with the surfactants before it is added to the aqueous phase
.




***Because this technique can cause the flavor to lose some of its potency,another approach is to use acosolvent system to incorporate the flavor.the use of ethanol,glycerin,or some appropriate solvent often provides acceptable results




.
Packaging,Storage,Labeling: -it is important to package emulsions in tight containers to minimize the evaporation of water from the product



-emulsions should be stored at room temperature or refrigerated.
-their label should include the instruction shake well.



Stability


:
*the stability of emulsion can be enhanced by
1-decreasing the globule size of the internal phase


2-obtaining an optimum ratio of oil in water


3-increasing the viscosity of the systemif the size of the globule is reduced to less than 5 micro M ,the stability and dispersion of the emulsion will increase(this reduction can be accomplished both with the shearing action of amortar and pestle with ahomogenizer




-
as the percentage of the internal phase increases,the viscosity of the product will also increase.




** alinear relationship exists between the viscosity of the emulsion and the viscosity of continous or external phase,,the viscosity of an emulsion generally increases on aging


**To improve the viscosity,the pharmac
ist can add a substance that is soluble in or miscible with the external phase of the emulsion




EX: In case of o/w emulsions:hydrocolloids can be used,,,whereas for w/o emulsions,waxes and viscous oils as well as fatty alcohols and fatty acids are appropriate.



****THE EMULSION IS STABLE WHEN:


It retains its original appearance,odor,color and other physical properties and when no creaming or coalescence occurs

.

**من المشاكل التى تواجة الصيدلى عند تحضير المستحلب والتى تؤثر على ثباتة:







1-CREAMING:


وهذا يحدث عندما تتجمع الجزيئات وتتركز فى طبقة معينة فى المستحلب
وهذة الظاهرة تؤدى الى التوزيع غير المتكافىء للدواء(المادة الفعالة) فى المستحلب

-In

o/w emulsions,creaming can be identified when one sees the oil globules gather and rise to the top

-creaming is easily reversible because the dispersed globules are still surrounded by the protective film

.
**فى بعض الاحيان يكون رج المستحلب سبب فى اعادة توزيع جزيئاتة

***

three methods that r used to minimize creaming
:

1-to enhance the viscosity of the external aqueous phase


2-to reduce the size of the globules to avery fine state with ahomogenizer


3-to adjust the denisities of both the internal and the external phases so that their densities are the same,,thus ,neither phase would tend to rise to the top or settle at the bottom



.
2-COALESCENSE
:


-contrary to creaming,,coalescence is an irreversible process becausethe film that surrounds the individual globules is destroyed

**altering the viscosity may help to stabilize globules and minimize their tendency to coalesce
.



3-PHASE INVERSION:

-it occurs when an emulsion inverts from one form to another(from o/w to w/o and vice versa)

**monovalent cations tend to form o/w emulsion,,whereas divalent cations tend to form w/o emulsion
.
EX:

-if sodium stearate is used to form o/w emulsion and then a calcium salt is added to form calcium stearate,,.The emulsion inverts from an o/w to a w/o type

4-flocculation


¯flocculation, an aggregation process. Flocculation occurs
when there is a net attractive force between droplets which is large enough to
overcome thermal agitation and cause persistent aggregation


- Whilst the droplets are held together they are not in intimate contact and are usually
separated by a layer of polymer or surfactant







رد باقتباس
قديم 05-03-2008, 05:18 PM #9
clinical pharma
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TOPICAL PREPARATIONS






*topically applied pharmaceuticals have 3 main functions:


1-to protect the injured area from the invironment and permit the skin to rejuvenate
.


2- to provide skin with hydration or to produce an emollient effect




3- to convey a medication for the skin, for specific effect either
topically or systemically.





1-ointements:



They r semisolid greasy preparations intended for external applications to the skin,nasal mucosa memberane,or rectum,which soften or melt at body temperature.



-the base is usually anhydrous and melt at body temperature











2-creams:



they r opaque soft solid or thick liquids intended for external application,consisting of medicaments dissolved or suspended in water washable or emollient bases











3-lotions


:
They r liquid preparations for external application without friction ,they r either dapped on the skin or applied on asuitable dressing and covered with waterproof dressing to reduce evaporation.







4-pastes:





They r semisolid preparation that differ from similar oint.and gels in that they contain ahigh proportion of solid ingredient medicament(finely powdered)


* the base may be anhydrous(liquid or soft paraffin) or water soluble(glycerol or mucilage).


The stiffness of the pastes provide them with protective coating
effect



.



5-poultics



They r paste-like preparation used externally to reduce pain&inflammationbecause they retain heat well


-after heating the preparation is spreadthickly on addressing and


applied -as hot as tolerated by the patient –to the affected are











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