Oral liquids such as syrups and suspensions are the preferred dosage form for pediatric and geriatric patients due to their ease of administration. Swallowing a tablet can be difficult for an infant or an elderly person and injectables usually require a qualified person to administer the drug.
Patient compliance in both these drastically decreases if the drug is extremely bitter and unpalatable. Hence, we need to cover the bitter taste of Active Pharmaceutical Ingredients (APIs) to make our dosage form pleasant for our customers. Taste masking also includes working on the overall appearance, smell, and texture of the dosage form to make the dosing experience pleasant for the patient. A gritty textured suspension or a neon green syrup for example would not make for a desirable dosage form.
The flavor profile of our oral liquid is also dependent on the target audience. While kids prefer flavors like bubble gum or cotton candy while elders prefer simpler flavors like vanilla. The flavor of the dosage form should be coherent with the taste and appearance of the syrup. For example, a cotton candy-flavored syrup or suspension cannot have a brown muddy color. Similarly, the syrup should smell like cotton candy to maintain the illusion. All these modifications to the dosage form will help us in increasing the patient’s adherence to the dosage regime thus improving treatment.
Factors Affecting Taste Masking:
Several factors affect the overall taste and appearance of the dosage form:
- Dose of administration
- Extent of bitterness
- Solubility of API
- Ionic properties of the API
- Drug particle size distribution
Popular techniques to taste-mask oral liquids:
Some of the popular techniques used for taste-masking oral liquids are:
- Adding sweeteners/ flavoring agents: This is one of the most popular techniques used for taste-masking. Adding sweeteners like sucrose or aspartame can mask the bitter taste of the drug providing us with a sweeter syrup that is easier to ingest. Similarly, strong flavors help in masking the bitter taste of the API. Some fruit flavors such as grapefruit can also confuse the patient into believing that the acidotic taste is from the grapefruit and not the bitter API. Using flavoring agents to taste-mask bitter API allows extra flexibility for the formulator since the flavor can be easily modified to suit the patient’s age group.
- Bitter Blockers: Certain excipients like the Bitter Bloc Pure help by blocking the bitter taste receptors on the tongue. This also helps in enhanced detection of the flavoring agent added to the formulation leading to efficient taste-masking.
- Viscosity Enhancers: Excipients like polyethylene glycol, propylene glycol, and gelatin help in increasing the viscosity of the oral liquid making it harder for the drug to reach the taste buds of the patient. It also helps in improving the mouthfeel for the patient in case of abrasive drugs. Acetaminophen solution is usually made sweeter with the help of microcrystalline cellulose and xanthan gum.
- Cyclodextrins: Cyclodextrins are sweet oligosaccharides with a cyclic structure essential in trapping the bitter API in their core. Cyclodextrins don’t usually hinder the drug release and can sometimes even increase the bioavailability of API. However, the release profile should be diligently monitored during the formulation stage to prevent ineffective dosing. The size of the drug molecule should not be too big as it will prevent complexation with cyclodextrin leading to ineffective taste masking.
- Taste-masking by salt formation, prodrug, or cocrystal formation: API molecules will have different physical and chemical properties based on their salt form. Formulators use this technique to enhance the solubility and taste of the API by creating salts or cocrystals with sweeter and more soluble molecules like cyclamate and aspartame. Sometimes, doing this can also help in increasing the overall physical stability of the API.
There are various techniques of taste-masking available today to provide a pleasant dosing experience to the patient. However, in cases where none of these techniques work, another approach that is gaining popularity is using Orally Disintegrating Tablets (ODTs). These are fast-dissolving tablets that disintegrate in the mouth without the need for water. These tablets are better for pediatric and geriatric patients who face difficulty swallowing conventional tablets.
Regulatory Aspects:
Certain taste-masking agents like cyclamates are carcinogenic when ingested in larger quantities. Thus, regulatory agencies can have stringent regulations around the use of these chemicals. Formulators need to ensure that the taste-masking agent is approved for use in the country they want to market their product in. The quantity of the chemical should also not exceed the recommended daily dose limit. USFDA has an Inactive Ingredients Database which enlists all the approved excipients for the pharmaceutical industry in the US.
Formulated for Success
Vici Health Sciences offers a team of expert formulators who have in-depth knowledge of taste-masking techniques and their regulatory aspects. In our experience, the most effective techniques for taste masking are using bitter blockers and viscosity enhancers. Sweetening agents in large quantities can act counteractively and impart a bitter taste to the formulation. We have also observed that identifying the right pH for the oral solution is also important as it can help in reducing the bitterness of the drug. We help our customers identify and achieve the perfect flavor and appearance profile for their formulation.
