Liquid medications are a common form of pharmaceutical preparation, allowing for easier administration, especially for children and older adults who have trouble swallowing tablets or capsules. A suspension is a specific type of liquid formulation that uses a unique physical structure to deliver the active drug ingredient. Understanding this structure and how it differs from other liquids is important for safe and effective use. Suspensions are frequently used for antibiotics, antipyretics like acetaminophen, and various other prescription and over-the-counter medicines.
Defining Drug Suspensions
A drug suspension is a liquid dosage form created as a two-phase system. It consists of a solid phase finely distributed throughout a liquid phase, known as the vehicle. The active drug ingredient is not dissolved in the liquid; instead, it remains as tiny, insoluble solid particles.
These particles typically range from 0.1 to 10 micrometers. Because solid drug particles are prone to settling due to gravity, pharmaceutical suspensions include stabilizing agents. These agents help keep the particles uniformly dispersed throughout the liquid, ensuring the medicine is consistent from one dose to the next.
How Suspensions Differ from Other Liquids
The difference between a suspension and a solution lies in the physical state of the drug. In a pharmaceutical solution, the drug substance is completely dissolved, resulting in a clear, single phase with no visible particles. Conversely, a suspension is a heterogeneous mixture where the drug is present as undissolved solid particles.
Because of these undissolved particles, suspensions appear cloudy or opaque, unlike a transparent solution. The particles will eventually settle to the bottom of the container, requiring mixing before administration. Other liquid forms, such as syrups or elixirs, are solutions where the drug is fully dissolved, so they do not separate and do not need to be shaken.
Why Medications Are Formulated as Suspensions
Formulating a medication as a suspension often relates to the chemical properties of the active drug ingredient. Many therapeutic compounds are not easily soluble in water or common liquid solvents, making the suspension form necessary. By keeping the drug as a solid particle, manufacturers can deliver the required dose without dissolving the substance.
A suspension also masks the naturally bitter taste of many drug compounds, which is important for pediatric medications. When the drug remains a solid particle, it has less direct contact with the taste receptors, making the medicine more palatable. This formulation can also improve the chemical stability of certain drugs that degrade quickly when fully dissolved.
Proper Handling and Dosage Instructions
The most important step for using any suspension medication is to shake the bottle well before measuring each dose. This action re-disperses the settled drug particles and ensures the medication is uniformly mixed. Failing to shake the bottle means the patient may receive a dose with too little or too much of the drug, leading to ineffective treatment or potential overdose.
Accurate measurement is equally important. Patients should always use the specific measuring tool provided, such as a dosing syringe, cup, or dropper, and never a household spoon. These specialized tools allow for precise measurement in milliliters (mL), the standard unit for liquid drug dosage. Always check the label for specific storage instructions, as some suspensions may require refrigeration after mixing or opening.