This document discusses floating drug delivery systems (FDDS). It defines FDDS as systems that have sufficient buoyancy to float over gastric contents and remain in the stomach for a prolonged period of time. This results in increased gastric retention and better control of drug concentrations. The document covers the importance of FDDS, factors affecting performance, classifications, suitable drugs, evaluation tests, and examples of marketed products. It provides details on the preparation and functioning of various FDDS types including non-effervescent, effervescent, raft forming, and hollow microspheres.

1. FLOATING DRUG
DELIVERY SYSTEM
IHTESHAM UR REHMAN
FINAL PROFF.
DEPARTMENT OF PHARMACY
HAZARA UNIVERSITY

2. DEFINITION
IMPORTANCE
STOMACH PHYSIOLOGY
MECHANISM OF FDDS
FACTORS AFFECTING FDDS
CLASSIFICATION
ADVANTAGES OF FDDS
SUITABLE DRUGS FOR FDDS
EVALUATION TESTS
CONCLUSION

3. DEFINITION
Floating systems are low-density systems that have sufficient
buoyancy to float over the gastric contents and remain buoyant in
the stomach without affecting the gastric emptying rate for a
prolonged period of time.
OR
Floating drug delivery system or hydrodynamically balance systems
have a bulk density lower than gastric fluid and thus remains
buoyant in the stomach for a prolonged period of time.
This results in an increased gastric retention time and a better
control of the fluctuations in plasma drug concentration.

4. IMPORTANCE
•Predetermined, predictable, and
controlled Release
•Maintenance of optimum therapeutic
drug concentration in blood
• Enhancement of activity and duration for short
half‐life drugs
•Reducing frequency of dosing and wastage of
drugs;
• Optimized therapy and better patient
compliances

5. IMPORTANCE CONTD.
•GASTRIC RETENTION
•INCREASED DRUG SOLUBILITY
•INCREASED GASTRIC RESIDENCE
TIME
•IMPROVES BIOAVAILABILITY
•REDUCES DRUG WASTAGE

8. MECHANISM OF FDDS
BUOYANCY
FDDS has a bulk density less than gastric
fluids and so remain buoyant in the
stomach with out affecting the gastric
emptying rate for a prolonged period of
time.
F = F buoyancy - F gravity = (Df - Ds) gv
Where, F= total vertical force,
Df = fluid density,
Ds = object density,
v = volume and
g = acceleration due to gravity.

9. FACTORS AFFECTING FLOATING TIME
a)FORMULATION FACTORS
Size of tablets
Density of tablets
Shape of Tablets
Viscosity Grade Polymer
b) IDIOSYNCRATIC FACTORS
Gender
Age
Posture
Concomitant Intake of
Drugs
Feeding Regimen

10. a) FORMULATION FACTORS
Size of tablets
Retention of floating dosage forms in stomach depends on the size of
tablets. Small tablets are emptied from the stomach during the
digestive phase, but large ones are expelled during the house keeping
waves.
Exp.

11. FF CONT.
Density of tablets
Density is the main factor affecting the gastric residence time of dosage form. A buoyant
dosage form having a density less than that of the gastric fluids floats, since it is away from
the pyloric sphincter, the dosage unit is retained in the stomach for a prolonged period. A
density of less than 1.0g/ml i.e. less than that of gastric contents has been reported.
Shape of tablets
The shape of dosage form is one of the factors that affect its gastric residence time. Six
shapes (ring tetrahedron, cloverleaf, string,
pellet, and disk) were screened in vivo for their gastric retention
potential. The tetrahedron (each leg 2cm long) rings (3.6 cm in
diameter) exhibited nearly 100% retention at 24 hr12.

12. FF CONT.
Viscosity grade of polymer
Drug release and floating properties of FDDS are greatly affected by
viscosity of polymers and their interaction. Low viscosity polymers
(e.g., HPMC K100 LV) were found to be more beneficial than high
viscosity polymers (e.g., HPMC K4M) in improving floating
properties. In addition, a decrease in the release rate was observed
with an increase in polymer viscosity.

13. IDIOSYNCRATIC FACTORS
Gender
Women have slower gastric emptying time than do men. Mean
ambulatory GRT in meals (3.4±0.4 hours) is less compared with
their age and race‐matched female counterparts (4.6±1.2 hours),
regardless of the weight, height and body surface.
Age
Low gastric emptying time is observed in elderly than do in younger subjects.
Intrasubject and intersubject variations also are observed in gastric and
intestinal transit
time. Elderly people, especially those over 70 years have a significantly
longer GRT.

14. IF CONT.
Posture
i) Upright position
An upright position protects floating forms against postprandial emptying because the
floating form remains above the gastric
contents irrespective of its size.
ii) Supine position
This position offers no reliable protection against early and erratic emptying. In
supine subjects large dosage forms (both conventional and floating) experience
prolonged retention. The gastric retention of floating forms appear to remain
buoyant anywhere between the lesser and greater curvature of the stomach. On
moving distally, these units may be swept away by the peristaltic movements that
propel the gastric contents towards the pylorus, leading to significant reduction in
GRT compared with upright subjects.

15. IF CONT.
Concomitant intake of drugs
Drugs such as prokinetic agents (e.g., metoclopramide and
cisapride), anti Cholinergics (e.g., atropine or propantheline),
opiates (e.g., codeine) may affect the performance of FDDS. The co
administration of GI‐motility decreasing drugs can increase gastric
emptying time.
Feeding Regimen

16. CLASSIFICATION
Single unit
floating dosage
systems
NON
EFFERVESCENT
EFFERVECENT
Multiple unit
floating dosage
systems
NON
EFFERVESCENT
EFFERVESCENT
RAFT FORMING
SYSTEMS
HOLLOW
MICROSPHERES
MAGNETIC SYSTEMS

17. SINGLE UNIT FLOATING DOSAGE SYSTEMS
Single unit dosage forms are easiest to develop but suffers from the
risk of losing their effects too early due to their all‐or‐none emptying
from the stomach and, thus they may cause high variability in
bioavailability and local irritation due to large amount of drug
delivered at a particular site of the gastro intestinal tract.

18. STEP 1
• Incorporating high level(20-75%w/w) gel-forming
hydrocolloids. E.g.:- HEC, HPC, Sod. CMC
STEP 2
• Mixing Drug Candidate With Hydrocolloids
STEP 3
• Compression To A Tablet Or Capsule
Step 4
• hydrophilic polymer swelling and buoyancy by
Entrapped Air, Bulk density >1
Step 5
•Errosion Of Gel Barrier
Step 6 •Release Of Drug By Diffusion Proceess
NON EFFERVESCENT SYSTEMS PREPARATION

19. EFFERVESCENT FLOATING DOSAGE FORM
• These are matrix type of systems with the help of swellable polymers
such as methylcellulose and chitosan ad various effervescent eg, sodium
bicarbonate, tartaric acid and citric acid.
• They are formulated in such a way that when in contact with the acidic
gas content ,CO2 is liberated and gets entrapped in swollen
hydrocolloids, which provides buoyancy to the dosage form.

20. MULTIPLE UNIT FLOATING DOSAGE SYSTEMS
Single unit formulations are associated with problems
such as sticking together or being obstructed in
gastrointestinal tract, which may have a potential
danger of producing irritation. Multiple unit
systems avoid the ‘all‐or‐none’ gastric emptying nature
of single unit systems. It reduces the intersubject
variability in absorption and the probability for dose
dumping is lower.

21. NON EFFERVESCENT SYSTEMS
LIMITED INFO. ABOUT THESE
LITERATURE reported the possibility of
developing such system containing indomethacin, using chitosan as
the polymeric excipient. A multiple unit HBS containing
indomethacin as a model drug prepared by extrusion process is
reported. A mixture of drug, chitosan and acetic acid is extruded
through a needle, and the extrudate is cut and dried. Chitosan
hydrates float in the acidic media, and the required drug release
could be obtained by modifying the drug‐polymer ratio.

22. EFFERVESCENT SYSTEMS
Sodium alginate solution is added dropwise to aq.
solution of CaCl2
Instant gelation of Droplet surface by formation of
Calcium alginate
Calcium Alginate beads are obtained and freeze dried
Porous structures are obtained by freeze drying
Porous Structure aid floating

23. ALGINATE BEADS
• Prepared by dropping sodium alginate solution into aqueous
solution of calcium chloride, causing the precipitation of
calcium alginate
• Freeze dry in liquid nitrogen at -40oc for 24h.
• Beads-spherical and 2.5 mm in diameter.

24. HOLLOW MICROSPHERES/FLOATING MICROSPHERES
• Hallow microspheres as one of the most promising buoyant systems, as they
possess unique advantages of multiple unit systems as well as better floating
properties, because of central hallow spaces inside the microsphere.
• The general techniques involved in their preparation include simple solvent
evaporation, and solvent diffusion and evaporation.

25. Techniques involved in their preparation include simple solvent evaporation,
and solvent diffusion and evaporation. The drug release and better
floating properties mainly depend on the type of polymer, plasticizer
and the solvents employed for the preparation. Polymers, such as
polycarbonate, Eudragit® S and cellulose acetate, are used in the
preparation of hollow microspheres, and the drug release can be
modified by optimizing the amount of polymer and the polymerplasticizer
ratio3

26. RAFT FORMING SYSTEMS
This system is used for delivery of antacids and drug delivery for treatment of
gastrointestinal infections and disorders.
The mechanism involved in this system includes the formation of a viscous
cohesive gel in contact with gastric fluids, forming a continuous layer called
raft.
The raft floats because of the buoyancy created by the
formation of CO2 and act as a barrier to
prevent the reflux of gastric contents like HCl and enzymes into the
esophagus. Usually, the
system contains a gel forming agent and alkaline bicarbonates or
carbonates responsible for the formation of to make the system less
dense and float on the gastric fluids.
Barrier formed by a raft -forming system

27. ADVANTAGES OF FDDS
•Enhanced bioavailability
•Sustained drug delivery/reduced frequency of dosing
•Targeted therapy for local ailments in the upper GIT
•Reduced fluctuations of drug concentration
•Improved selectivity in receptor activation
•Reduced counter-activity of the body
•Extended effective concentration.
•Minimized adverse activity at the colon

28. DISADVANTAGES OF FDDS
• The drug substances that are unstable in the acidic environment of
the stomach are not suitable candidates to be incorporated in the
systems.
• These systems require a high level of fluid in the stomach for drug
delivery to float and work efficiently.
• Not suitable for drugs that have solubility or stability problem in
GIT.

29. SUITABLE DRUGS FOR FDDS
1. Narrow absorption window in GI tract, e.g., riboflavin and
Levodopa
2. Basically absorbed from stomach and upper part of GIT, e.g.,
chlordiazepoxide and cinnarazine.
3. Drugs that disturb normal colonic bacteria, e.g., amoxicillin
trihydrate.
4. Locally active in the stomach, e.g., antacids and misoprostol.
5. Drugs that degrade in the colon, e.g., ranitidine HCl and
metronidazole.

30. EVALUATION TESTS:
IN-VITRO TEST
Floating lag time
Floating time
Dissolution study
Resultant weight test
IN-VIVO TEST
X ray method
Gamma-scintigraphy
Gastroscopy
Ultra sonography

31. PRE-COMPRESSION TESTS
• Angle of repose
• Tapped density and
bulk density
• Carr’s compressibility
index and hausner
ratio
• Size and shape
POST COMPRESSION TESTS
• Thickness
• Diameter
• Hardness test
• Weight variation test
• Friability test
• Content uniformity
test

32. Floating lag time:
•The time between the introduction of the tablet into
the medium and its rise to upper one third of the
dissolution vessel is termed as floating lag time.
Floating time:
•The time for which the dosage form floats is termed
as the floating or flotation time.

33. Marketed Products of FDDS
Brand name Delivery system Drug (dose) Company
name
Valrelease® Floating capsule Diazepam (15mg) Hoffmann-LaRoche,
USA
Madopar® HBS
(Prolopa® HBS)
Floating, CR capsule Benserazide (25mg) and L-
dopa (100mg)
Roche Products,
USA
Liquid Gaviscon® Effervescent Floating
liquid alginate
preparations
Al hydroxide (95 mg), Mg
Carbonate (358 mg)
GlaxoSmithkline,
India
Topalkan® Floating liquid alginate
Preparation
Al – Mg antacid Pierre Fabre Drug,
France
Conviron® Colloidal gel forming
FDDS
Ferrous sulphate Ranbaxy, India
Cytotech® Bilayer floating capsule Misoprostol
(100μg/200μg)
Pharmacia, USA
Cifran OD® Gas-generating floating Ciprofloxacin (1gm) Ranbaxy, India

34. Widely used drug and dosage forms
Sr
No.
Dosage
Form
Drugs
1. MICROSPHERE Aspirin, Griseofulvin, p-nitroglycerine, ibuprofen, Terfinadine,
Tranilast.
2. GRANULES Diclofenac sodium, Indomethacin, Prednisolone
3. FILMS Cinnarizine
4. CAPSULE Chlrdiazepoxide, Diazepam, Furosemide, L-Dopa, Benserazide,
Misoprostol, Propanolol
5. TABLET/ PILLS Acetaminophen, ASA, Amoxicilin Trihydrate,Ampicilin, Atenolol,
Chlorphenarimine,Cinnazirine, Diltiazem,Flourouracil, Isosorbide
Mononitrate & dinitrate, p-aminobenzoic acid, Prednisolone,
Quinidine Gluconate,Ribiflavin 5-p, Sotalol,Theophylline, Verapamil