PA20285 MEDICINES DESIGN- formulations of pharmaceutical products Flashcards Preview

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What are the advantages of pharmaceutical oral solutions?

Easier to swallow (for elderly and infants)
faster therapeutic response than tablets; drug is already dissolved and is ready for absorption.
The BA of oral solutions is better than oral solid doses.
They are homogenous systems with uniform distribution of the drug throughout the preparation-(no issues with phase separation As with emulsions and suspensions as these are SOLUTIONS)
Reduced irritation due to immediate dilution by gastric contents
Tastes of bitter therapeutic agents can be masked by adding sweetners etc (this may be harder to do with tablets)


What are pharmaceutical oral solutions?

Oral Solutions are liquid preparations, intended for oral administration, that contain one or more substances with or without flavoring, sweetening, or coloring agents dissolved in water or cosolvent-water mixtures. They are things like cough medicine and gaviscon medicine


What are the disadvantages with oral solutions?

Problems involved with manufacture and transport (breakage of bottles)
Grown of a microorganism (bacteria) may occur if it becomes contaminated.
Poor stability of ingredients in a solution. (better stability in solid form).
Solutions have a shorter shelf life than solids forms.
Dose accuracy is harder to get correct eg. Using 5ml spoon may not be done accurately.
Unsuitable for drugs that are chemically unstable in water.
Expensive to ship + bulky to carry.


What factors must be considered when making the solution?

Homogeneity of solution; phases mustn't separate.
Solubility; drug must be soluble to be made into solution.
If solubility is high at the selected pH of formulation, the drug can be readily out into solution.
If solubility is low at selected pH, alternative dosage form should be used as solution not appropriate (eg suspension with surfactants)
If solubility is moderate, use co solvents to enhance solubilty.


What is a common vehicle to use for oral solutions?

Purified water USP
this has low cost & low toxicity


Common co solvents to use when increasing solubilty of a moderately soluble drug?

Glycerol (contains 3 OH GROUPS increasing solubility)
Alcohol USP
Propylene glycol USP

Can also use SURFACTANTS to increase solubilty


What are common excipients of pharmaceutical oral solutions?

Buffers (control pH)
Sweetners (nicer taste)
Viscosity enhancing agents (so they're easier to pour onto measuring spoon)


What do antioxidants do?

Increase the stability of a drug (if it's degraded by oxidation)
Antioxidants are oxidised and degraded in preference to the drug therefore they'd protect the drug from degradation.


What do preservatives do?

Control microorganisms that may get into the solution.
Have anti microbial activity.
Are chemically and physically stable.
Low toxicity
Eg. Benzoin acid and it's salts, sorbic acid and it's salts, alkyl esters of PArahydroxybenzoic acid
Remember preservatives don't make solutions sterile, just reduce microbes. Becomes unsterile as soon as touched and opened


What needs to be considered for effectiveness of preservatives?

Minimum inhibitory concentration(MIC) of preservative
May sure other excipients and pH don't effect preservative concentration
Need to consider factors that mAy effect preservative efficacy
PH of formulation may have an effect
Presence of micelles/ hydrophillic polymers may reduce the free concentration of preservatives


How does the pH of the formulation effect the action of preservatives?

Use of acidic preservatives can sometimes be problematic
Acidic preservatives are used however.
Mechanism of action; preservative diffuses into cytoplasm of microorganism and the neutral conditions makes the acidic preservative dissociate making the cytoplasm acidic and stopping further growth of the microorganism.
PH effects the amount of acidic preservative present at a particular pH.


How do micelles contribute to oral solutions/ what's there effect on preservatives?

They increase the solubilisation of lipophillic drugs.
Usually drug is inside micelle to increase solubility.
Preservatives may have lipophillic properties, therefore they may partition into micelles and decrease the availability of micelles to solubilise the drug, and also decrease the amount of active preservative available to kill microbes.
You can avoid this by increasing the amount of preservative as this will increase the free fraction of active preservative.


How do the presence of hydrophilic polymers effect preservatives in oral solutions?

The free concentration fraction of preservatives is decreased in the presence of hydrophilic polymers.
This is because preservatives chemically interact with the polymers.
To get around this problem you need to increase the concentration of preservatives in the formulation.
Cat ionic polymers should not be used in conjunction with acidic preservatives!


What are the 4 taste sensations?

Bitter , sweet, sour, salty


What are flavour adjuncts?

Things you add with flavours to the solution to desensitise the taste receptors in the mouth so that bad tasting parts are blocked.
Examples of adjuncts= methanol and chloroform


Why add colourants to solutions?

May add to match the flavour eg green with mint flavoured, orange with citrus flavour


What if I have a poorly soluble drug in water?

You won't be able to to use it as an oral solution, only a suspension.
Can't solubilise a really poorly soluble drug, therefore it's best to use a different formulation.


What if my drug in a bottle appears to be cloudy?

Expiry date
Opened/damaged bottle
Check for contamination


What are the 3 main types of solutions administered orally?

Oral solutions
Oral syrups
Oral exilirs


What is the usual pH of oral solutions?

Ph 7
Unless there's issues regarding solubility of the drug
Formulated over a broad ph range


All components of an oral solution should be soluble! No precipitation



Tell me some things about oral syrups?

Highly concentrated with sugar/ sugar substitute as a flavouring agent
Need to be careful with the choice of vehicle eg. Orange flavoured syrup is acidic which may decrease the solubilty of acidic drugs.
Drugs can be directly incorporated into syrup


What are the components of oral syrups?

Purified water
Sugar/ sugar substitutes (60-80%) contribute to the viscosity. May use non sucrose bases like sorbitol solution USP.
May want sugar free syrups (for children and diabetic patients) sugar free syrups require inclusion of a viscosity modifying agent.
if there's a high concentration of sucrose then preservatives arent needed.
Flavours- of natural origin or synthetic flavours (certain flavours may have mild therapeutic activity eg antacids giving a minty taste)
Remember; preservatives aren't necessarily needed for syrups and exilirs


What are oral elixirs?

Clear hydro alcoholic solutions
Concentration of alcohol is sufficient to ensure that all the other components remain in solution
Presence of alcohol may be a problem for patients who wish to avoid it
Preservatives are not needed in elixirs with over 12 % alcohol as this is antimicrobial (but preservatives are always required in oral solutions , just not in elixirs or some syrups)


What are linctuses?

Viscous preparations
Drug is dissolved in a vehicle containing a high % sucrose
Primary for treatment of cough (has soothing actions on mucous membrane)


What are mouth washes and gargles for?

For treatment of infection and inflammation of the oral cavity


What are enemas?

For rectal administration
Used for clearance of the bowel
Soften faeces
Osmotic laxatives (increasing water in bowel)


What are oral suspensions?

Dispersions in which the drug is dispersed in the external phase (vehicle)
Solubility of drug in the vehicle is low


What makes an acceptable suspension?

Low rate of sedimentation
The disperse phase is easily redispersed with gentle shaking
Has to have good flow so it can easily be poured
Aesthetically pleasing (look attractive)
Suspensions can be admitstered orally, parenterally, topically


Problems with oral suspensions?

Because the suspension is not homogeneous when not shaken, will we get the correct dose of drug..?
Difficult to make them look nice
Bulky to carry

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