Powders for oral suspension are preparations consisting of solid, loose, dry particles of varying degrees of fine particle size. They are developed as powder mixtures of typical ingredients required for an aqueous suspension. As indicated previously in the article “liquid dosage forms: pharmaceutical suspensions” these official preparations have “for Oral Suspension” in their official title to distinguish them from prepared suspensions (that is, suspensions that are available in ready-to-use form from the manufacturer).
Powders for suspension are marketed as oral reconstitutable medications in unit-dose sachet or multidose bottles. Most drugs prepared as a dry mix for oral suspension are antibiotics. They may contain excipients, in particular, to facilitate dispersion or dissolution and to prevent caking.
The popularity of this dosage form is due to the inherent physical instability of suspensions and the desirability of a relatively long shelf life.
Types of Powder for oral suspension
a. Unit dose/ single dose powders for oral suspension
A unit dose sachet of powder could be administered to a patient by sprinkling on the top of a semisolid food, such as jelly or ice cream, or by suspending in a suitable vehicle, such as water or juice, immediately before administration. This mode of administration is preferred for paediatric and geriatric populations, who may have swallowing difficulty, and for high dose compounds.
A key requirement for this dosage form is the palatability of the drug. Extremely bitter or unpleasant tasting drugs are generally not suitable for formulation as powder for suspension.
b. Multidose powders for oral suspension
The multidose powders for oral suspension are dispensed as powders in a suitable-sized bottle for reconstitution with water by the pharmacist immediately before dispensing. Superior stability of the powder dosage form allows long shelf life of the commercial product at room temperature of a drug that is very unstable in the presence of water.
The reconstituted suspension has a limited shelf life under designated storage conditions, such as 14 days under refrigeration.
Ideal properties of powder for suspension
The quality attributes of a suspension reconstituted from a powder for suspension are same as those of a suspension that is marketed in a ready-to-use form. In addition, there are quality requirements for the unit dose powder for suspension powder sachets or the multidose powder for suspension powder in a bottle. These include
- Fill amount: The amount of powder per container must be tightly controlled to be as close as possible to the amount listed on the label. For a unit dose container, the dispensable or deliverable amount, in addition to the label amount, is measured.
- Reconstitution time: As powders for suspension are meant for reconstitution by the patient or the pharmacist the suspension should be readily formed on addition of water and reasonable manual agitation.
- Uniformity of content: Container-to-container uniformity of content of the powder for suspension is important to assure uniformity of the drug amount dispensed across different containers.
- Physical and chemical stability: The powder for suspension must maintain physical and chemical stability throughout the labelled shelf life under the labelled storage conditions.
How to reconstitute oral suspensions
Steps used when reconstituting oral suspensions:
Step 1: Determine the type and volume of diluent needed
Step 2: Gently shake the bottle to loosen the powder. Open the cap of the bottle.
Step 3: For antibiotic bottles with markings, carefully add cool boiled water to about half the height of the final marking on the bottle. As for antibiotic bottles without markings, please refer to the antibiotic’s packaging, patient information leaflets provided by the manufacturer or your pharmacist for information on the required volume of water to mix the dry powder antibiotic. You may use a marked measuring cup to measure the required amount of water.
Step 4: Replace the cap of the bottle. Shake the bottle until all the powder is thoroughly mixed.
Step 5: Allow the suspension to stand for about 2-5 minutes to rid the air bubbles in the bottle.
Step 6: Open the cap. Carefully add water till the final marking on the bottle.
Step 7: Replace the cap of the bottle. Invert the bottle and shake the bottle vigorously for at least 5 seconds to get an even suspension. Make sure the medication has dispersed completely before administering to the patient.
Administration of oral suspension
Step 8: Shake the prepared suspension well before giving each dose. To make sure that you are giving the right dose, use the measuring tool that comes with the drug e.g. oral syringe, measuring spoon or a calibrated medication cup. If the drug does not come with a measuring tool, you may ask your pharmacist to recommend one.
Do not use a kitchen teaspoon or tablespoon as they are not accurate.
Storage of reconstituted powder for oral suspension
Step 9: The suspension should either be stored in the refrigerator or kept at room temperature in a cool dry place below 25 – 30 oC unless otherwise stated. Do not freeze the preparation.
Step 10: Discard any remaining suspension upon expiry as advised after reconstitution.
Note: If you have more than one bottle of the same suspension, finish one bottle before mixing the second one.
Examples of antibiotic drugs for oral suspension
- Cefuroxime axetil for Oral Suspension, USP (Ceroxim for Oral Suspension, Sun Pharmaceutical)
- Cephalexin for Oral Suspension, USP (Ascend Laboratories)
- Fluconazole for Oral Suspension, USP (Aurobindo)
- Doxycycline for Oral Suspension, USP (Vibramycin Monohydrate for Oral Suspension, Pfizer)
- Cefpodoxime Proxetil for Oral Suspension, USP (Rising Cefpodoxime Proxetil for Oral Suspension, Rising Pharmaceuticals, Inc.)
- Cefixime for Oral Suspension, USP (Suprax Powder for Oral Suspension, Lupin Pharma)
- Azithromycin for Oral Suspension, USP (Teva Pharmaceutical Industries Ltd.)
- Amoxicillin for Oral Suspension, USP (Amoxil for Oral Suspension, GlaxoSmithKline)
- Allen, L. and Ansel, H. (2014). Ansel’s Pharmaceutical Dosage Forms and Drug Delivery Systems (10th ed.). Philadelphia, Lippincott Williams & Wilkins.
- Mahato, R and Narang, A. (2018). Pharmaceutical Dosage Forms and Drug Delivery (3rd ed.). New York: Taylor & Francis Group, LLC.
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