liposome
DESCRIPTION
LipoSomeTRANSCRIPT
What is a liposome?What is a liposome?
– Spherical vesicles with a phospholipid bilayerSpherical vesicles with a phospholipid bilayer
Hydrophilic
Hydrophobic
Uses of LiposomesUses of LiposomesChelation therapy for treatment of heavy metal
poisoningEnzyme replacementDiagnostic imaging of tumors
Study of membranesCosmetics
Drug Delivery
Why Use Liposomes in Drug Why Use Liposomes in Drug Delivery?Delivery?
Inactive: Unmodified liposomes gather in specific tissue reticuloendothelial system
Active: alter liposome surface with ligand (antibodies, enzymes, protein A, sugars)
Directly to site
Physical: temperature or pH sensitive liposomes
Drug Targeting
ProtectionDecrease harmful side effects
Pharmokinetics - efficacy and toxicityChanges the absorbance and biodistribution
Change where drug accumulates in the body
Protects drug
Deliver drug in desired formMultidrug resistance
Why Use Liposomes in Drug Delivery?
ReleaseAffect the time in which the drug is released
Prolong time -increase duration of action and decrease administration
Dependent on drug and liposome properties Liposome composition, pH and osmotic gradient, and
environment
Why Use Liposomes in Drug Delivery?
Modes of Liposome/Cell Modes of Liposome/Cell Interaction Interaction
Adsorption Endocytosis
Fusion Lipid transfer
Liposomes Help ImproveLiposomes Help ImproveTherapeutic indexRapid metabolismUnfavorable pharmokineticsLow solubilityLack of stabilityIrritationCustom designLipid contentSize
Surface chargeMethod of preparation
Current liposomal drug Current liposomal drug preparationspreparations
Type of Agents ExamplesAnticancer Drugs
Anti bacterial
AntiviralDNA materialEnzymes
RadionuclideFungicidesVaccines
*Currently in Clinical Trials or Approved for Clinical Use
Malaria merozoite, Malaria sporozoiteHepatitis B antigen, Rabies virus glycoprotein
Amphotericin B*In-111*, Tc-99m
Hexosaminidase A Glucocerebrosidase, Peroxidase
Duanorubicin, Doxorubicin*, Epirubicin Methotrexate, Cisplatin*, CytarabinTriclosan, Clindamycin hydrochloride, Ampicillin, peperacillin, rifamicinAZTcDNA - CFTR*
No decrease in effectiveness of drug against fungi
Liposomal Formulation of AmB
Decrease in toxicity
Exact Mechanism of liposomes not understood
Cholesterol - only few %moles
Phospholipid:AmB ratio
DiffusionLipid transfer
AmB
Lipid
Problems with Liposomal Problems with Liposomal Preparations of DrugsPreparations of Drugs
$$$$ Fungizone $40.58 Amphotec $2334Doxil $1200 per treatment, twice the cost of normal protocol
of chemotherapy and drugs
Lack long term stability (short shelf life)
Freeze dry and pH adjustment
Low “Pay Load” - poor encapsulation
Physical and chemical instability
Polar drugs and drugs without opposite chargeModifications
Studies with insulin show that liposomes may be an effective way to package proteins and peptides for use
Clinical Trials for several liposomal formulations More studies on the manipulation of liposomes
Future
JournalsAllen, Theresa M. "Liposomal Drug Formulations: Rationale for Development and What We Can
Expect for the Future." Drugs 56: 747-756, 1998.Allen, Theresa M. "Long-circulating (sterically stabilized) liposomes for targeted drug delivery ."
TiPs 15: 214-219, 1994.Allen, Theresa M. "Opportunities in Drug Delivery." Drugs 54 Suppl. 4: 8-14, 1997Janknegt, Robert. "Liposomal and Lipid Formulations of Amphotericin B." Clinical Pharmacokinetics.
23(4): 279-291, 1992. Kim, Anna et al. "Pharmacodynamics of insulin in polyethylene glycol-coated liposomes."
International Journal of Pharmaceutics. 180: 75-81, 1999.Quilitz, Rod. "Oncology Pharmacotherapy: The Use of Lipid Formulations of Amphotericin B in Cancer
Patients." Cancer Control.5:439-449, 1998. Ranade, Vasant V. "Drug Delivery Systems: Site-Specific Drug Delivery Using Liposomes as Carriers."
Pharmacology. 29: 685-694, 1989. Storm, Gert and Daan J.A. Crommelin. "Liposomes:quo vadi?" PSTT 1: 19-31, 1998. Taylor, KMG and JM Newton. "Liposomes as a vecicle for drug delivery." British Journal of Hospital
Medicine. 51: 55-59, 1994
WebsitesJames, John S. "Doxil Approved for KS." www.immunet. org.imminet/atn.nsf/page/a-235-03.Wasan, Ellen. "Targeted Gene Transfer." Member.tripod.com/~rrishna/lipos1.html"Introduction to Controlled Drug Delivery Systems." www5.bae.ncsu.edu/bae/reearch/blak…
k/otherprojects/drugDeliver_97/http://www. Mssm.edu/medicine/thrombosis/phosphol.html"Doxorubicin." http://tirgan.com/adria.htm"Clinical Pharmacology Online." http://www.cponline.gsm.com/scripts/fullmono/showmono. "Drugstore.com" http://www.drugstore.com/pharmacy/prices/Amphotec."Sequus' Doxil Becomes First Liposome Product Approved In U.S." www.slip.net/~mcdavis/
database/doxor_1"Liposomes." www.collabo.com/liposom0.htmPaustin, Timothy. “Cellular Membranes.”www.bact.wisc.edu/microtextbook/bacterialstructure/Membranegen.htmlwww.cbc.umn.edu/~mwd/cell_www/chapter2/membrane.html#PHOSPHOLIPIDS
BooksJones, Macolm N. and Chapman, David. Micelles, Monolayers and Biomembranes. Wiley-Liss. New York (1995).
Garrett, R. and Grisham C. Biochemistry, 2nd ed. Saunders Colleges Publishing. New York (1999). 264.