When a person needs medication, liquid forms often offer an easier way to take the required dose than pills. An oral suspension is a uniform mixture where solid drug particles are dispersed throughout a liquid base. This formulation allows patients who struggle with swallowing tablets or capsules to receive their necessary treatment effectively. Understanding how this mixture is formulated and handled ensures the medication works as intended.
Defining Oral Suspension
The technical composition of an oral suspension involves several specific components working together to maintain stability. At its core is the active pharmaceutical ingredient (API), which is the solid drug reduced to very fine particles. These particles are intentionally formulated to be insoluble or only slightly soluble within the liquid component.
The liquid component, known as the vehicle, is most often purified water, although non-aqueous liquids are sometimes used. A pharmaceutical suspension requires the addition of suspending agents, which are specialized substances that increase the liquid’s viscosity. By thickening the vehicle, these agents help slow down the rate at which the solid drug particles settle at the bottom, a process called sedimentation.
This thickened base temporarily holds the drug particles evenly throughout the liquid. While these agents improve stability, they do not prevent sedimentation entirely. Therefore, the drug particles will eventually settle, necessitating a specific action before the medication is administered.
Suspension vs. Solution
Differentiating an oral suspension from other liquid medicines, like solutions and syrups, is important for understanding proper use. The key distinction lies in the physical state of the active drug component within the liquid base. In an oral solution, the drug substance is completely dissolved into the liquid, much like sugar dissolving in hot tea.
Because the drug is fully dissolved in a solution, the mixture is homogenous and never separates. Syrups are similar to solutions but contain a high concentration of sugar or a sugar substitute, which functions as a preservative and flavoring agent. In contrast, an oral suspension contains drug particles that remain physically separate from the liquid, similar to sand stirred into water.
These fine, undissolved particles give a suspension its cloudy or opaque appearance, unlike the clear appearance of most solutions. Since the solid drug naturally settles out over time, the preparation must be treated differently to ensure the patient receives the full and correct dose. This physical difference between dissolved and suspended particles directly impacts how the medication must be handled by the patient.
Why Suspensions are Used
The formulation of medication as an oral suspension offers advantages related to pharmaceutical chemistry and patient compliance. The primary chemical reason for using this form is to deliver drugs that are inherently insoluble in water or other common solvents. Formulating the drug as fine, suspended particles allows for effective administration without costly chemical modification.
Suspensions benefit patients who have difficulty taking traditional solid dosage forms. For pediatric or geriatric patients who struggle to swallow tablets or capsules, the liquid format provides an easier way to consume the required medicine. This ease of swallowing helps ensure the patient completes the full course of treatment as prescribed.
The suspension vehicle aids in taste masking, improving patient acceptance, especially for children. By physically coating the bitter drug particles with the flavored, viscous liquid, the vehicle minimizes contact with the taste buds. This mechanism makes otherwise unpalatable medications acceptable to the patient.
Proper Handling and Administration
Because the drug particles in a suspension will eventually settle, proper handling and administration techniques are required to ensure dosing accuracy.
Shaking and Mixing
The most important step before every use is to vigorously shake the bottle to redisperse the settled drug particles evenly throughout the liquid vehicle. This action must be performed immediately prior to measuring a dose so that the medicine is uniform when the patient takes it. Shaking the container ensures that every measured dose contains the correct concentration of the active drug, preventing under-dosing or over-dosing. If the suspension is not properly mixed, the first doses taken will be too weak, while the final doses will contain a highly concentrated, potentially dangerous amount of the drug.
Accurate Measurement
Accurate measurement of the dose requires using the correct device provided by the pharmacy, such as an oral syringe or a specially marked dosing cup. Household measuring spoons, like those used for cooking, are highly inaccurate and should never be used for measuring liquid medication. Using the pharmacy-provided tool helps ensure the patient receives the exact milliliter volume prescribed by the healthcare provider.
Storage and Stability
Patients must adhere to the storage instructions provided on the label, as these differ between various suspension formulations. Some suspensions must be refrigerated to maintain stability, while others must be kept at room temperature. It is also important to note the discard date, especially for suspensions mixed by the pharmacist, as they are only stable for a limited time after reconstitution.