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Definition, Classification, Advantages and Disadvantages of Suspensions

Different types of suspensions based on administration, solid content, particle size and advantages and disadvantages of suspensions.
Drugs with insoluble solid particles can be dispersed in a liquid medium to form a suspension. This gives a greater capability of administering drugs that could be difficult to administer to some patients such as kids and the elderly. Most drug manufacturers prefer pharmaceutical suspensions over the solution dosage.

Classification of Pharmaceutical Suspensions
A. Classification based on the route of administration
1. Oral Suspension: These suspensions are administered orally for instance paracetamol suspension.
2. Parenteral Suspension: The intravenous or intramuscular routes are used to administer such drugs mostly through injections. Its example is sodium benzylpenicillin.
3. Tropical Suspension: These are suspensions that are used for external purposes. They are applied to the external part of a patient’s body that is aching.
4. Ophthalmic Suspension: This is a suspension that is used to treat aching eyes. Its particles should be very fine, not irritating, sterile and isotonic.

B. Classification based on solid particles proportion
1. Dilute Suspension: This suspension contains solid weights that range between 2% to 10% per volume. An example is the cortisone acetate suspension.
2. Concentrated Suspension: The solid weight per volume in these solutions is 50%. An example is the Zinc oxide suspension.

C. Classification based on the size of dispersed particles
1. Molecular Dispersion: The size of particles in this suspension is not greater than 1µm.
2. Colloidal Dispersion: Its particle size is between 0.1µm-0.2µm
3. Coarse Dispersion: The particle size in this suspension is always greater than 0.2µm.

Advantages of Pharmaceutical Suspension
1. It eases the delivery of low soluble therapeutic agents
Therapeutic agents which are lowly soluble can be administered through a suspension. Despite them being soluble, it requires a large volume of a solvent. This volume may compromise the storage of the agent when it comes to precipitation issues.
2. It facilitates the dispersion of bitter drugs
Not all drugs administered to patients have a sweet taste. The majority of them are bitter especially when administered to kids who might, by all means, avoid using the drugs. Through the suspensions, the bitterness is reduced to a minimal level making the patient to complete the dosage of the specific drug. It is also an alternative method of administering drugs to patients who have difficulties swallowing solid drugs.
3. It increases the bioavailability of drug dosage
Most drug dosages might appear in just one form such as capsule only. This form might restrict the way of administering the drug to specific patients. Through the suspension form, this challenge can be solved.
4. Provides controlled drug delivery
Due to the diverse options of administering drugs, it might be difficult to administer some drugs in other forms other than the suspension form. For instance, drugs to be injected into a patient’s muscles require it be in suspension form.
5. It provides proper storage of drugs
Drugs in suspension form are resistant to degradation effects such as oxidation or hydrolysis. With the aid of suspension, drug manufactures therefore opt for suspension-form drugs to help keep them safe for a while before they are administered.

Disadvantages of Pharmaceutical Suspensions
1. They are fundamentally unstable
This limitation affects the time in which a suspension can appear on the shelf. The more it stays, the more its physical stability is reduced. This forces manufacturers to include many skills in order to retain the stability of the drug.
2. It is not possible on aesthetic pharmaceuticals
When aesthetic pharmaceuticals suspensions are manufactured, their elegance is not achieved. This limits the way these drugs can be presented on the suspension form.
3. Difficult to administer the correct dosage
Drugs that are administered in suspension form are difficult to determine the correct dosage. It is not unless the suspensions are presented in unit dosage for doctors or nurses to know the exact dosage to be given to their patients.
4. It may be inconvenient to be carried by patients
Suspension drugs can be formulated in a bulky manner that patients can find it difficult to carry. When a patient is prescribed many drugs of this form, he/she might prefer to avoid using the drugs while traveling due to their bulkiness.
5. It is subjected to difficulties during administering
There are some conditions such as shaking well before use, that ought to be followed before administering pharmaceutical suspension. When such conditions are omitted, the right dosage won’t be achieved. Similarly, such drugs can get poured or might be difficult to syringe when need be. The drugs can also form crystals making it difficult to break the suspensions.
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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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