Nanosuspension:A novel drug delivery system

Abstract

During the last two decades, many modern technologies have been established in the pharmaceutical research and development area. The automation of the drug discovery process by technologies such as high-throughput screening, combinatorial chemistry, and computer- aided drug design is leading to a vast number of drug candidates possessing a very good efficacy. Unfortunately, many of these drug candidates are exhibiting poor aqueous solubility. The use of drug nanosuspension is an universal formulation approach to increase the therapeutic performance of these drugs in any route of administration. A nanosuspension is a submicron colloidal dispersion of drug particles which are stabilized by surfactants. Nanosuspension is defined as very finely dispersed solid drug particles in an aqueous vehicle for either oral and topical use or parenteral and pulmonary administration. The particle size distribution of the solid particles in nanosuspensions is usually less than one micron with an average particle size ranging between 200 and 600 nm. Nanosuspension consists of the pure poorly water-soluble drug without any matrix material suspended in dispersion.This review article describes the physicochemical properties of drug nanosuspension, preparation methods and; its potential clinical advantages.

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Suryakanta Nayak et al. / Journal of Pharmacy Research 2010, 3(2),241-246
Journal of Pharmacy Research Vol.3.Issue 2.February 2010 241-246
Review Article
ISSN: 0974-6943 Available online through
www.jpronline.info
*Corresponding author.
Suryakanta Nayak
Department of Pharmaceutics, L.B.Rao Institute of Pharmaceutical Educa-
tion and Research, B.D.Rao College Campus, Bethak Road, Khambhat,
Anand, Gujarat-388620
Tel.: + 91-9924947587, 02698223455
Telefax: +91-
E-mail:suryakanta.k@gmail.com
INTRODUCTION
Nanosuspension:A novel drug delivery system
Suryakanta Nayak*, Dibyasundar Panda1, Jagannath Sahoo2.
1Department of Pharmaceutics, Institute of Pharmacy & Technology, Salipur, Cuttack, Orissa-754202
2Department of Pharmaceutics Royal College of Pharmacy & Health Sciences Andhapasara Road, Berhampur ,Ganjam, Orissa – 760002
Received on: 23-09-2009; Revised on: 17-11-2009; Accepted on:05-01-2010
ABSTRACT
During the last two decades, many modern technologies have been established in the pharmaceutical research and development area. The automation of the
drug discovery process by technologies such as high-throughput screening, combinatorial chemistry, and computer- aided drug design is leading to a vast
number of drug candidates possessing a very good efficacy. Unfortunately, many of these drug candidates are exhibiting poor aqueous solubility. The use of
drug nanosuspension is an universal formulation approach to increase the therapeutic performance of these drugs in any route of administration. A
nanosuspension is a submicron colloidal dispersion of drug particles which are stabilized by surfactants. Nanosuspension is defined as very finely dispersed
solid drug particles in an aqueous vehicle for either oral and topical use or parenteral and pulmonary administration. The particle size distribution of the solid
particles in nanosuspensions is usually less than one micron with an average particle size ranging between 200 and 600 nm. Nanosuspension consists of the
pure poorly water-soluble drug without any matrix material suspended in dispersion.This review article describes the physicochemical properties of drug
nanosuspension, preparation methods and; its potential clinical advantages.
Keywords: Nanosuspension; Bioavailability enhancement; Surfactants; Stabilizers.
The formulation of poorly water soluble drugs has always
been a challenging problem faced by pharmaceutical scientists and it
is expected to increase because approximately 40% or more of the
new chemical entities being generated through drug discovery
programmes are poorly water-soluble1. Obviously poorly water-soluble
drugs show many problems in formulating them in conventional dos-
age forms. One of the critical problems associated with poorly soluble
drugs is too low bioavailability and/or erratic absorption2. The prob-
lem is even more intense for drugs such as itraconazole and
carbamazepine (belonging to Biopharmaceutical Classification Scheme
Class II(BCS CLASS II)) as classified by BCS System3,4 as they are
poorly soluble in both aqueous and organic media, and for those
drugs having a log P value of 2. The performance of these drugs is
dissolution rate-limited (for Class II and III drugs) and is affected by
the fed/fasted state of the patient. Dissolution rates of sparingly
soluble drugs are related to the shape as well as the particle size.
Therefore decrease in particle size results in an increase in dissolu-
tion rate5.
There are number of strategies to resolve the problems of
low solubility and low bioavailability. The strategies include
micronization6, solublization using co-solvents, use of permeation
enhancers, oily solutions, surfactant dispersions6, salt formation7 and
precipitation techniques8,9. These techniques for solubility enhance-
ment have some limitations and hence have limited utility in solubility
enhancement. Micronization by colloid mills or jet mills increases the
dissolution velocity of drug due to increase in surface area but does
not increase the saturation solubility6.
Other techniques like liposomes10,emulsions,and micr
oemulsions11, solid-dispersions12 and inclusion complexes using
Cyclodextrins13 show reasonable success but they lack in universal
applicability to all drugs. These techniques are not applicable to the
drugs, which are not soluble in both aqueous and organic Medias.
Hence there is need of some different and simple approach to tackle
the formulation problems to improve their efficacy and to optimize the
therapy with respect to pharmacoeconomics.
Nanosuspensions have revealed their potential to tackle the
problems associated with the delivery of poorly water-soluble and
poorly water-and lipid-soluble drugs, and are unique because of their
simplicity and the advantages they confer over other strategies. This
review focuses on the various aspects of nanosuspensions and their
potentials as promising strategy in drug delivery. Nanotechnology is
defined as the science and engineering carried out in the nanoscale
that is 10-9 meters14. The drug microparticles/micronized drug powder
is transferred to drug nanoparticles by techniques like Bottom Up
Technology (precipitation) and Top Down Technology15,16 or disinte-
gration methods. Nano is a Greek word, which means ‘dwarf’. Nano
means it is the factor of 10-9 or one billionth. Some comparisons of
nanoscale are given below,
0.1 nm = Diameter of one Hydrogen atom
2.5 nm = Width of a DNA molecule17.
1micron = 1000nm.
1nm = 10-9m= 10-7cm = 10-6mm.
micron = 10-6m= 10-4cm = 10-3mm.

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Nanosuspensions can be defined as colloidal dispersions
of nano-sized drug particles that are produced by a suitable method
and stabilized by a suitable stabilizer. Nanosuspensions consist of
the pure poorly water-soluble drug without any matrix material sus-
pended in dispersion 18. It is sub-micron colloidal dispersion of pure
particles of drug stabilized by surfactants19. By formulating
nanosuspensions problems associated with delivery of poorly water-
soluble drugs and poorly water-soluble and lipid-soluble drugs can
be solved. Nanosuspensions differ from nanoparticles20, which are
polymeric colloidal carriers of drugs (Nanospheres and nanocapsules),
and from solid-lipid nanoparticles21 (SLN), which are lipidic carriers of
drug. Preparing nanosuspensions is preferred for the compounds
that are insoluble in water (but are soluble in oil) with high log P value.
Conventionally the drugs that are insoluble in water but soluble in oil
phase system are formulated in liposome, emulsion systems but these
lipidic formulation approaches are not applicable to all drugs. In these
cases nanosuspensions are preferred. In case of drugs that are in-
soluble in both water and in organic media instead of using lipidic
systems nanosuspensions are used as a formulation approach.
Nanosuspension formulation approach is most suitable for the com-
pounds with high log P value, high melting point and high dose22.
METHODS OF PREPARATION
Mainly there are two methods for preparation of
nanosuspensions. The conventional methods of precipitation (Hy-
drosols23) are called ‘Bottom Up technology’. In Bottom Up Technol-
ogy the drug is dissolved in a solvent, which is then added to non-
solvent to precipitate the crystals. The basic advantage of precipita-
tion technique is the use of simple and low cost equipments. The
basic challenge of this technique is that during the precipitation pro-
cedure the growing of the drug crystals needs to be controlled by
addition of surfactant to avoid formation of microparticles. The limita-
tion of this precipitation technique is that the drug needs to be soluble
in atleast one solvent and this solvent needs to be miscible with
nonsolvent. Moreover precipitation technique is not applicable to
drugs, which are simultaneously poorly soluble in aqueous and non-
aqueous media23. And the other is ‘Top Down Technologies’ are the
disintegration methods and are preferred over the precipitation meth-
ods. The ‘Top Down Technologies’ include Media Milling
(Nanocrystals), High Pressure Homogenization in water (Dissocubes),
High Pressure Homogenization in nonaqueous media (Nanopure) and
combination of Precipitation and High-Pressure Homogenization
(Nanoedege) 15,16. Few other techniques used for preparing
nanosuspensions are emulsion as templates, microemulsion as tem-
plates22.
Media Milling (Nanocrystals or Nanosystems)
This patent-protected technology was developed by
Liversidge et al (1992). Formerly, the technology was owned by the
company Nano Systems but recently it has been acquired by Elan
Drug Delivery. In this method the nanosuspensions are produced
using high-shear media mills or pearl mills. The media mill Consists of
a milling chamber, a milling shaft and a re circulation chamber (Fig-
ure1). The milling chamber is charged with t he milling media, water,
drug and stabilizer, as depicted in Figure1, and the milling media or
pearls are then rotated at a very high shear rate. The milling process is
performed under controlled temperatures.22,23,24
Figure1: Schematic representation of the media milling process.
The milling chamber charged with polymeric media is the
active component of the mill. The mill can be operated in a batch or
recirculation mode. Crude slurry consisting of drug, water and stabi-
lizer is fed into the milling chamber and processed into a nanocrystalline
dispersion. The typical residence time generated for a nanometer-
sized dispersion with a meandiameterof<200nmis30–60min.
Principle:
The high energy and shear forces generated as a result of
the impaction of the milling media with the drug provide the energy
input to break the micro particulate drug into nano-sized particles.
The milling medium is composed of glass, zirconium oxide or highly
cross-linked polystyrene resin. The process can be performed in ei-
ther batch or recirculation mode. In batch mode, the time required to
obtain dispersions with unimodal distribution profiles and mean
diameters<200nm is 3060 min. The media milling process can success-
fully process micronized and non-micronized drug crystals. Once the
formulation and the process are optimized, very little batch- to-batch
variation is observed in the quality of the dispersion.
Advantages
•Media milling is applicable to the drugs that are poorly soluble in both
aqueous and organic media.
•Very dilute as well as highly concentrated nanosuspensions can be pre-
pared by handling 1mg/ml to 400mg/ml drug quantity.
•Nanosize distribution of final nanosize products.
Disadvantages
•Nanosuspensions contaminated with materials eroded from balls may
be problematic when it is used for long therapy.
•The media milling technique is time consuming.
•Some fractions of particles are in the micrometer range.
•Scale up is not easy due to mill size and weight.
Figure 2: Schematic representation of the high- pressure homog-

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Journal of Pharmacy Research Vol.3.Issue 2.February 2010 241-246
enization process.
High-pressure homogenizers (DissoCubes) 18,25,26
Disso Cubes technology was developed by R. H. Muller
(Muller et al1998). The patent rights of Disso Cubes were initially
owned by DDS (Drug Delivery Services) GmbH but currently they are
owned by Skye Pharma plc. Disso Cubes are engineered using pis-
ton-gap-type high-pressure homogenizers. A commonly used homog-
enizer is the APV Micron LAB 40 (APV Deutschland GmbH, Lubeck,
Germany). However, other piston gap homogenizers from Avestin
(Avestin Inc., Ottawa, Canada) and Stansted (Stansted Fluid Power
Ltd, Stansted, UK) can also be used. A high-pressure homogenizer
(Figure2) consists of a high-pressure plunger pump with a subse-
quent relief valve (homogenizing valve). The task of the plunger pump
is to provide the energy level required for the relief. The relief valve
consists of a fixed valve seat and an adjustable valve. These parts
form an adjustable radial precision gap. The gap conditions, the resis-
tance and thus the homogenizing pressure vary as a function of the
force acting on the valve. An external impact ring forms a defined out
let cross-section and prevents the valve casing from being damaged
due to the flow (Jahnke 1998). The Instrument is available in discon-
tinuous and continuous versions. The continuous version is suitable
for optimizing the various parameters of the homogenization process.
Use of the discontinuous version is sensible if the drug is very costly
or of limited availability. The instrument can be operated at pressures
varying from 100 to 1500 bars. In some instruments, a maximum pres-
sure of 2000 bars can be reached. High-pressure homogenizers are
available with different capacities ranging from 40mL (for laboratory
purposes) to a few thousand liters (for large-scale production).
It is advisable to start with the micronized drug (particle
size<25 µm) for production of nano suspensions in order to prevent
blocking of the homogenization gap. Hence, generally a jet milled
drug is employed as the starting material for producing Disso Cubes.
Before subjecting the drug to the homogenization process, it is es-
sential to form a presuspension of the micronized drug in surfactant
solution using high speed stirrers. During the homogenization pro-
cess, the drug suspension is pressed through the homogenization
gap in order to achieve nano-sizing of the drug.
Principle:
During homogenization, the fracture of drug particles is
brought about by cavitation, high-shear force sand the collision of
the particles against each other. The drug suspension, contained in a
cylinder of diameter about 3mm, passes suddenly through a very
narrow homogenization gap of 25 µm, which leads to a high streaming
velocity.
In the homogenization gap, according to Bernoulli’s equation, the
dynamic pressure of the fluid increases with the simultaneous de-
crease in static pressure below the boiling point of water at room
temperature. In consequence, water starts boiling at room tempera-
ture, leading to the formation of gas bubbles, which implode when the
suspension leaves the gap (called cavitation) and normal air pressure
is reached again. The implosion forces are sufficiently high to break
down the drug microparticles into nanoparticles. Additionally, the
collision of the particles at high speed helps to achieve the nanosizing
of the drug. To improve the efficiency of nanosizing, the addition of
viscosity enhancers is advantageous in certain cases as increasing
the viscosity increases the powder density within the dispersion zone
(homogenization gap).
Advantages
•Drugs that are poorly soluble in both aqueous and organic media
can be easily formulated into nanosuspensions.
•Ease of scale-up and little batch-to-batch variation (Grauetal2000).
•Narrow size distribution of the nano particulate drug Present in
the final product (Muller&Bohm1998).
•Allows a septic production of nanosuspensions for parenteral
administration.
•Flexibility in handling the drug quantity, ranging from1 to 400mg
mLµ-1, thus enabling formulation of very dilute as well as highly
concentrated nanosuspensions (Krause & Muller 2001).
Disadvantages
•Prerequisite of micronized drug particles.
•Prerequisite of suspension formation using high-speed mixers
before subjecting it to homogenization.
Emulsions as templates
Apart from the use of emulsions as a drug delivery vehicle,
they can also be used as templates to produce nanosuspensions.
The use of emulsions as templates is applicable for those drugs that
are soluble in either volatile organic solvent or partially water-mis-
cible solvent. Such solvents can be used as the dispersed phase of
the emulsion. There are two ways of fabricating drug nano suspen-
sions by the emulsification method. In the first method, an organic
solvent or mixture of Solvents loaded with the drug is dispersed in the
aqueous phase containing suitable surfactants to form an emulsion.
The organic phase is then evaporated under reduced pres- sure so
that the drug particles precipitate instantaneously to form a nano
suspension stabilized by surfactants. Since one particle is formed in
each emulsion droplet, it is possible to control the particle size of the
nanosuspension by controlling the size of the emulsion. Optimizing
the Surfactant composition increases the intake of organic phase and
ultimately the drug loading in the emulsion. Originally, organic sol-
vents such as methylene chloride and chloroform were used27. How-
ever, environmental hazards and human safety concerns about re-
sidual solvents have limited their use in routine manufacturing pro-
cesses. Relatively safer solvents such as ethyl acetate and ethyl for-
mate can still be considered for use28,29.
Another method makes use of partially water miscible sol-
vents such as butyl lactate, benzyl alcohol and triacetin as the dis-
persed phase instead of hazardous solvents30. The emulsion is formed
by the conventional method and the drug nanosuspension is ob-
tained by just diluting the emulsion. Dilution of the emulsion with
water causes complete diffusion of the internal phase into the exter-
nal phase, leading to instantaneous formation of a nanosuspension.
The nanosuspension thus formed has to be made free of the internal
phase and surfactants by means of diultrafiltration in order to make it
suitable for administration. However, if all the ingredients that are
used for the Production of the nanosuspension are present in a con-
centration acceptable for the desired route of administration, then
simple centrifugation or ultracentrifugation is sufficient to separate
the nanosuspension.
Advantages
•Use of specialized equipment is not necessary.
•Particle size can easily be controlled by controlling the size of the
emulsion droplet.

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•Ease of scale-up if formulation is optimized properly.
Disadvantages
•Drugs that are poorly soluble in both aqueous and organic
media can not be formulated by this technique.
•Safety concerns because of the use of hazardous solvents in
the process.
•Need for diultrafiltration for purification of the drug
nanosuspension, which may render the process costly.
•High amount of surfactant / stabilizer is required as com-pared
to the production techniques described earlier.
The production of drug nanosuspensions from emulsion tem-
plates has been successfully applied to the poorly water-soluble and
poorly bioavailable anti-cancer drug mitotane, where a significant
improvement in the dissolution rate of the drug (five-fold increase) as
compared to the commercial product was observed30.
Microemulsions as templates
Microemulsions are thermodynamically stable and
isotropically clear dispersions of two immiscible liquids, such as oil
and water, stabilized by an interfacial film of surfactant and co surfac-
tant31. Their advantages, such as high drug solublization, long shelf
life and ease of manufacture, make them an ideal drug delivery ve-
hicle. Recently, the use of microemulsions as templates for the pro-
duction of solid lipid nanoparticles32 and polymeric nanoparticles33
has been described. Taking advantage of the micro emulsion struc-
ture, one can use microemulsions even for the production of nano-
suspensions34. Oil-in-water microemulsions are preferred for this pur-
pose. The internal phase of these microemulsions could be either a
partially miscible liquid or a suitable organic solvent, as described
earlier.
The drug can be either loaded in the internal phase or pre-
formed microemulsions can be saturated with the drug by intimate
mixing. The suitable dilution of the microemulsion yields the drug
nanosuspension by the mechanism described earlier. The influence
of the amount and ratio of surfactant to co surfactant on the uptake of
internal phase and on the globule size of the microemulsion should be
investigated and optimized in order to achieve the desired drug load-
ing. The nanosuspension thus formed has to be made free of the
internal phase and surfactants by means of diultrafiltration in order to
make it suitable for administration. However, if all the ingredients that
are used for the production of the nanosuspension are present in a
concentration acceptable for the desired route of administration, then
simple centrifugation or ultracentrifugation is sufficient to separate
the nanosuspension. The advantages and disadvantages are the same
as for emulsion templates. The only added advantage is the need for
less energy input for the production of nanosuspensions by virtue of
microemulsions.
FORMULATION CONSIDERATION
Stabilizer
Stabilizer plays an important role in the formulation of
nanosuspensions. In the absence of an appropriate stabilizer, the
high surface energy of nanosize particles can induce agglomeration
or aggregation of the drug crystals. The main functions of a stabilizer
are to wet the drug particles thoroughly, and to prevent Ostwald’s
ripening35 and agglomeration of nanosuspensions in order to yield a
physically stable formulation by providing steric or ionic barriers.
The drug-to-stabilizer ratio in the formulation may vary from 1:20 to
20:1 and should be investigated for a specific case. Stabilizers that
have been explored so far include cellulosics, poloxamers, polysor-
bates, lecithins and povidones36.
Organic solvents
Organic solvents may be required in the formulation of
nanosuspensions if they are to be prepared using an emulsion or
microemulsion as a template. The pharmaceutically acceptable and
less hazardous water-miscible solvents, such as ethanol and isopro-
panol, and partially water-miscible solvents, such As ethyl acetate,
ethyl formate, butyl lactate, triacetin, propylene carbonate and benzyl
alcohol, are preferred in the formulation over the conventional haz-
ardous solvents, such as dichloromethane. Additionally, partially water
miscible organic solvents can be used as the internal phase of the
microemulsion when the nanosuspensions are to be produced using
a microemulsion as a template.
Co-surfactants
The choice of co-surfactant is critical when using micro emul-
sions to formulate nanosuspensions. Since co surfactants can greatly
influence phase behavior, the effect of co-surfactant on uptake of the
internal phase for selected microemulsion composition and on drug
loading should be investigated. Although the literature describes the
use of bile salts and dipotassium glycerrhizinate as co-surfactants,
various solubilizers, such as Transcutol, glycofurol, ethanol and iso-
propanol, can be safely used as co-surfactants in the formulation of
microemulsions.
Other additives
Nanosuspensions may contain additives such as buffers,
salts, polyols, osmogent and cryoprotectant, depending on either the
route of administration or the properties of the drug moiety.
ADVANTAGES OF NANOSUSPENSIONS
Physical Long-term Stability
Dispersed systems show physical instability due to Ostwald
ripening which is responsible for crystal growth to form microparticles.
Ostwald ripening is caused due to the difference in dissolution veloc-
ity/ saturation solubility of small and large particles. In
nanosuspensions all particles are of uniform size hence there is little
difference between saturation solubility of drug particles. Ostwald
ripening is totally absent in nanosuspensions due to uniform particle
size, which is also responsible for long-term physical stability of
nanosuspensions37.
Increase in Saturation Solubility and Dissolution Velocity of drug
Dissolution of drug is increased due to increase in the sur-
face area of the drug particles from micrometers to the nanometer size.
According to Noyes-Whitney equation (equation no.1\ dissolution
velocity increase due to increase in the surface area from micron size
to particles of nanometer size.
Dx /dt = [( D x A/ h] [Cs-X/V] —————————(1)
Where D is diffusion coefficient, A is surface area of particle, dx/dt is
the dissolution velocity, V is volume of dissolution medium and X is
the concentration in surrounding liquid.

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Journal of Pharmacy Research Vol.3.Issue 2.February 2010 241-246
According to the Prandtl equation, for small particles the
diffusional distance h decreases with decreasing particle size. The
decrease in h increases Cs (saturation solubility) and leads to an
increase in gradient (Cs-Cx)/h and thus to an increase in the dissolu-
tion velocity. According to Ostwald-Freunddlich equation decrease
in particle size below 1µm increases the intrinsic solubility or satura-
tion solubility.
Internal structure of Nanosuspensions
The high-energy input during disintegration process causes
structural changes inside the drug particles. When the drug particles
are exposed to high-pressure homogenisation particles are transformed
from crystalline state to amorphous state. The change in state de-
pends upon the hardness of drug, number of homogenisation cycles
chemical nature of drug and power density applied by
homogeniser23,37.
APPLICATIONS OF NANOSUSPENSIONS IN DRUG DELIVERY
Oral drug delivery
The oral route is the preferred route for drug delivery be-
cause of its numerous well-known advantages. The efficacy or per-
formance of the orally administered drug generally depends on its
solubility and absorption through the gastrointestinal tract. Hence, a
drug candidate that exhibit s poor aqueous solubility and / or disso-
lution rate limited absorption is believed to possess slow and/or highly
variable oral bioavailability.
Danazol is poorly bioavailable gonadotropin inhibitor, showed a
drastic improvement in bioavailability when administered as a
nanosuspension as compared to the commercial danazol
macrosuspension Danocrine. Danazol nanosuspension led to an ab-
solute bioavailability of 82.3%, where as the marketed danazol sus-
pension Danocrine was 5.2% bioavailable38.
Parenteral drug delivery
From the formulation perspective, nanosuspensions meet
almost all the requirements of an ideal drug delivery system for the
parenteral route. Since the drug particles are directly nanosized, it
becomes easy to process almost all drugs for parenteral administra-
tion. Hence, nanosuspensions enable significant improvement in the
parenterally tolerable dose of the drug, leading to a reduction in the
cost of the therapy and also improved therapeutic performance.
The maximum tolerable dose of paclitaxel nanosuspension
was found to be three times higher than the currently marketed Taxol,
which uses Cremophore EL and ethanol to solubilize the drug39.
Ocular drug delivery
Nanosuspension can also be used for the drugs that exhibit
poor solubility in lachrymal secretions. To achieve sustained release
of the drug for a stipulated time period, nanosuspension can be incor-
porated in a suitable hydrogel base or mucoadhesive base or even in
ocular inserts. The designed polymeric nanosuspensions revealed
superior in-vivo activity over the existing marketed formulations and
could sustain drug release for twenty four hours40.
Pulmonary drug delivery
Nanosuspension can be used for delivering drugs that ex-
hibit poor solubility in pulmonary secretions. Currently such drugs
are delivered as suspension aerosol or as dry powder inhalers. The
drugs used in suspension aerosols and dry powder inhalers have
micron size particle.
Budesonide is poorly water -soluble corticosteroid, has been
success fully formulated as a nanosuspension for pulmonary deliv-
ery41.
Targeted drug delivery
Nanosuspension can be used for targeted deliver as their
surface properties & changing of the stabilizer can easily alter in vivo
behavior. Their versatility and ease of scale up and commercial pro-
duction enables the development of commercially viable
nanosuspensions for targeted drug delivery. Kayser developed the
formulation of aphidicolin as a nanosuspension to improve the drug
targeting effect against Leishmania-infected macrophages, and stated
that aphidicolin was highly active at a concentration in the microgram
range42.
CONCLUSION
Poor aqueous solubility is rapidly becoming the leading
hurdle for formulation scientists working on drug delivery of various
drug compounds and leads to employment of novel formulation tech-
nologies. The use of drug nanosuspension is a universal formulation
approach to increase the therapeutic performance of these drugs in
any route of administration. Almost any drug can be reduced in size
to the nanometer range. Production techniques such as media milling
and high pressure homogenization have been successfully employed
for large-scale production of nanosuspensions. The advances in pro-
duction methodologies using emulsions or micro emulsions as tem-
plates have provided still simpler approaches for production but with
limitations. Further investigation in this regard is still essential.
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Source of support: Nil, Conflict of interest: None Declared
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