Pharmaceutical suspensions are dispersion of particulate drug(s) in a liquid medium (usually aqueous) in which the drug is not readily soluble. Doses formulated as suspensions can be divided into oral suspensions, powder for oral suspensions or suspensions prepared from powdered tablets or capsule contents, etc.
In an ideal suspension, particles are uniformly dispersed, free from aggregation. Even if sedimentation occurs, particles should be resuspended upon mild agitation.
Like any other dosage form, pharmaceutical suspension has witnessed various technological innovations over the years in an urge to improve acceptance, bioavailability, altered disposition, drug targeting, etc.
The aim of this article is to give the reader an overview of advancement in suspension technologies. Patents related to these advancements are also discussed.
Advancements in Pharmaceutical Suspensions
Recent advancements in pharmaceutical suspension include:
- Nano suspension
- Taste masked suspension
- Sustained-release suspensions
- Aqueous suspension
Nanosuspensions are submicron colloidal dispersions of nanosized drug particles stabilized by surfactants. It can also be defined as sub-micron colloidal dispersions of discrete drug particles, ranging from 100 to 1,000 nm, stabilized with polymers or surfactants, or a mixture of both.
Nanosuspensions consist of the poorly water-soluble drug without any matrix material suspended in dispersion. The dispersion medium for nanosuspensions is generally aqueous but it can also be hydro-alcoholic or non-aqueous.
Patents related to nanosuspensions include:
- Aqueous nanosuspension formulation comprising a drug possessing low intrinsic water solubility e.g. amidarone.
- Compositions and methods for preparing oral nanosuspensions of poorly soluble drugs with improved bioavailability.
- Nanosuspension of antifungal azole derivatives particularly itraconazole, with improved bioavailability.
- Systems with strongly increased saturation solubility which is obtained by preparing nanosuspensions of medicaments.
2. Taste masked suspension
Taste masking is defined as a perceived reduction of an undesirable taste that would otherwise exist. A Number of taste-masking technologies have been used to address the problem of bitter tastes of some pharmaceutical formulation which might result in decreased patient compliance to a medication. These include:
- Addition of sweeteners, flavors & Amino acids
- Taste Masking by Inclusion Complexation
- Taste Masking by Ion-Exchange Resins
- Taste Masking by Coating
- Taste Masking by effervescent agent
- Taste Masking by microencapsulation
- Taste Masking by rheological modifications
- Taste Masking by salt preparation
- Taste Masking by solid dispersion systems
- Taste Masking by wax embedding of drug
- Taste Masking by group alteration and prodrug approach
- Taste Masking by incorporation of drug into liposomes
- Taste Masking by the use of multiple emulsions
- Taste Masking by freeze-drying process
Patents related to taste-masked suspension include:
- Dry taste-masked powder comprising a steroid or its salts or derivatives and pharmaceutically accepted excipient.
- Preparation method of taste-masked suspension granule of Gegenqinlian decoction.
- Pharmaceutical acceptable composition in the form of suspension for oral delivery of dexamethasone acetate in which the active ingredient is homogenously dispersed in a pharmaceutically accepted aqueous carrier-vehicle.
3. Sustained-release suspensions
Sustained release dosage forms are formulations designed to release a drug at a predetermined rate and prolonged therapeutic effect over an extended period of time in order to maintain a constant drug concentration for a period of time with minimum side effect.
In the formulation of sustained-release suspensions, the drug susbstance is coated with insoluble polymer which provides sustained release and also in the process masks the taste of bitter drugs. The polymers that have found use in the formulation of sustained-release suspensions are ethylcellulose, eudragit, cellulose acetate.
Patents related to sustained release suspensions include:
- Montmorillonite combined propranolol sustained-release dry suspension.
- Parenteral pharmaceutical formulation or composition in suspension, having sustained release, containing suspended particles of estradiol and progesterone for hormonal replacement in female mammals in low and ultralow dosage.
- Gliclazide oral sustained dry-mixed suspension.
- Stable, sustained-release oral liquid suspension dosage form of pharmaceutical active ingredients which is easy to administer and particularly beneficial for the pediatric and geriatric patients, etc.
4. Aqueous suspension
An aqueous suspension is a useful dosage form for administering an insoluble or poorly water-soluble drug. It as a pharmaceutical suspension as a particle suspension whose suspending phase is composed of water.
Aqueous suspensions are intended for oral, ophthalmic, inhalation, and topical applications.
Related Patents to aqueous suspensions include:
- Pharmaceutical formulation comprising an aqueous suspension of an androstane derivative for the treatment of inflammatory and allergic conditions.
- Aqueous preparation prepared by incorporating in an aqueous suspension of a hardly soluble drug, a water-soluble polymer within the concentration range from the concentration at which surface tension of the aqueous suspension of the drug begins to decrease up to the concentration at which the reduction in surface tension ceases, etc.
- Aulton, M. and Taylor, K. (2013). Aulton’s Pharmaceutics: The Design and Manufacture of Medicines, (4th ed.). Edinburgh: Churchill Livingstone.
- Badhe, G., Bhutada, M., Chandran S., Deshmukh, A., Gore, B. and Kulkarni, S.(2012). Taste-Masked Powder for suspension Compositions of MethylPrednisolone. WO201101734 A3.
- Barret E. R. (2004). Nanosuspensions in drug delivery. Nature Reviews, 3, 785–96.
- Biggadike K., Buxton L., Coote S., Nice R., Reed K., Sayani A. and Sharma A. (2005). Pharmaceutical Formulation Comprising an Aqueous Suspension of an Androstane Derivative for the Treatment of Inflammatory and Allergic Conditions. US20050164996 A1.
- Chen S., Guo K. and Zhou J. (2012). Preparation Method of Taste-Masked Suspension Granules of Gegenqinlian Decoction. CN102309562 (A).
- Cheng Q. and Lin Y. (2012). Montmorillonite Combined Propranolol Sustained-Release Dry Suspension, Preparation Method thereof and Preparation Method of Na- Montmorillonite used in Propranolol Sustained-Release Dry Suspension. CN102406616 (A).
- Ge, H. and Jun, T. (2011). Oral Sustained –Release Dry-Mixed Suspension and Preparation Method Thereof. CN102028660.
- Gedar, S., Kataria, M., Bilandi, A. and Taneja, R. (2013). Advancements and Patents in Pharmaceutical Suspension Technologies. Journal of Biological and Scientific Opinion, 1(14), 372-380. http://dx.doi.org/10.7897/2321%E2%80%936328.01420 accessed on 10/09/2016.
- Jaun., A.U., Vilboeuf S. and Claude J. (2012). Parenteral Pharmaceutical Formulation in Suspension, having Sustained Release, in Low and Ultralow Dosage, in Hormonal Therapy in the Limacteric Syndrome. EP2520301 A2.
- Kassotakis (2010). Oral Suspension of Dexamethasone Acetate- Taste Masking Composition of Dexamethasone. WO2010119300.
- Mohan, G., Nagesh, N., Rakesh S., Sujay, R. and Akash, J. (2011). Sustained Release Oral Liquid Suspension Dosage Form. WO2011107855.
- Muller, R., Gohla, S., Dingler, A., and Schneppe, T. (2000). Large-scale Production of solid-lipid Nanoparticles (SLN) and Nanosuspension (Dissocubes). In D.Wise (Ed.) Handbook of pharmaceutical controlled release technology (pp. 359-375). New York: Marcel Dekker.
- Narkhede, K. (2015). A Brief Review on Nano-pharmaceutical Technology. Journal of Pharmaceutical Science and Bioscientific Research, 5(5), 520-528.
- Nickerson, B. (2011). Sample Preparation of Pharmaceutical Dosage Forms: Challenges and Strategies for Sample Preparation and Extraction. New York: Springer.
- Yasueda, S., Matsuhisa, K., Terayama, H. and Inada, K. (2002). Aqueous Suspension with Good Redispersibility. US6448296 B2.