Liquid medications offer a versatile way to deliver active ingredients, especially for individuals who find it challenging to swallow pills or capsules, such as children or the elderly. These liquid forms are precisely formulated for accurate dosing and come in various types. Understanding the distinctions between these preparations helps clarify how they work and why specific forms are chosen, as their unique compositions dictate proper handling and administration.
What Makes a Medication a Suspension?
A suspension medication contains solid drug particles dispersed throughout a liquid medium. Unlike other liquid forms where the drug completely dissolves, these particles remain undissolved and are finely distributed. This means the solid particles can settle at the bottom of the container over time if left undisturbed. Suspension particles are typically larger than those in a solution, often ranging from 1 to 1000 micrometers. This characteristic necessitates shaking the bottle thoroughly before each use to ensure active ingredients are evenly distributed for a consistent and accurate dose.
The physical nature of a suspension is comparable to a snow globe, where particles settle when still but disperse when shaken. Manufacturers often incorporate suspending agents to help keep these particles dispersed and increase the liquid’s viscosity, which slows down the settling process. Even with these agents, redispersion upon shaking remains an important property of a well-formulated suspension.
Reasons for Using Suspension Medications
Suspension formulations are often chosen for drugs with low water solubility. Many new drugs are poorly soluble, making suspensions a practical way to administer these therapeutic agents. While a drug might be solubilized in a solution, a large volume of solvent required or potential precipitation issues during storage can make a suspension a more suitable option.
Suspensions are also used to mask the unpleasant or bitter taste of certain medications, which is beneficial for pediatric patients. The liquid medium, often enhanced with flavors and sweeteners, makes the medication more palatable and easier for children and adults with swallowing difficulties to take. Additionally, suspensions can improve the chemical stability of certain drugs that degrade quickly in a dissolved state. By maintaining the drug in a solid, undissolved form, it is less prone to chemical reactions with the liquid vehicle, potentially extending its shelf life. Controlled or sustained release of the drug over time can also be achieved with suspension formulations, as the solid particles gradually dissolve and are absorbed by the body.
Suspensions Compared to Other Liquid Forms
To understand suspensions, it helps to differentiate them from other common liquid medication forms like solutions and emulsions. Solutions are homogeneous mixtures where the active drug is completely dissolved in a solvent, resulting in a clear and uniform liquid. Because the drug is fully integrated, solutions do not require shaking before use as the concentration remains consistent throughout.
In contrast, emulsions involve two immiscible liquids, like oil and water, dispersed within each other. These mixtures often appear milky or cloudy, similar to milk. While emulsions may appear visually similar to suspensions due to their cloudy nature, the main difference lies in the dispersed phase: suspensions have solid particles in a liquid, whereas emulsions have liquid droplets dispersed in another liquid. Unlike suspensions, which contain solid particles that can settle, emulsions maintain their dispersed state due to emulsifying agents that stabilize the mixture of liquids.
How to Properly Use and Store Suspensions
Proper usage of suspension medications ensures correct dosage and effectiveness. It is important to shake the bottle thoroughly before each dose to redistribute any settled solid drug particles evenly throughout the liquid. This step ensures that each measured dose contains the accurate amount of medication prescribed. Failure to shake can result in receiving too little medication at the beginning of the bottle and potentially too much at the end, leading to ineffective treatment or overdose.
Accurate measurement of the dose is also essential. Patients should always use the specific measuring device provided with the medication, such as an oral syringe, dosing spoon, or medicine cup, rather than household spoons. Household spoons are not standardized and can lead to inaccurate dosing. After use, wipe the bottle clean to prevent residue from obscuring the label.
Most suspensions, especially those reconstituted by a pharmacist, may require refrigeration and often have a limited shelf life, typically 7-14 days. Store medications in a cool, dry place, away from heat, moisture, and direct light, and always out of reach of children. Always check the specific storage instructions on the medication label and dispose of any unused medication after its expiration date or the recommended period after opening.