Brain Targeted Drug Delivery System : Brain Targeted Drug Delivery System 1 Presented by -
Mr. Dholariya Yatin N.
Master of Pharmacy(QAT)
MARATHWADA MITRA MANDAL’S COLLEGE OF PHARMACY
THERGAON,PUNE CONTENTS : CONTENTS 2 Introduction
Anatomy of Brain
Barriers to CNS drug delivery
Factor affecting drug permeation through BBB
Transport at the BBB
Strategies for enhanced brain drug delivery
References INTRODUCTION : INTRODUCTION 3 The drug accessibility to the CNS is mainly limited by the BBB.
Insufficient amount of drug reaches to the brain. Therefore practical strategies are required.
New strategies are arise from investigation that critically reveals the physiological mechanism involved with the solute transport across BBB.
Several classes of metabolic substrates, peptides , plasma derived –proteins and various group of centrally active pharmacotherapeutics are able to utilize specialized `shuttle’ services at the BBB. Slide 4: ANATOMY OF BRAIN The human nervous system comprises of CNS, ANS, PNS.
Brain is sensitive & complex organ of human body, that comes under CNS along with spinal cord.
The delivery of drugs to CNS is a challenge in the treatment of neurological disorders.
The major neurological diseases are categorized as neurodegerative, cerebrovascular, inflammatory (infections or autoimmune) and cancer. 4 cont… : The brain has 4 fluid compartments
- Blood- flows through entire brain
- Interstitial fluid (ISF)- bathing neurons and neuroglia
- Cerebrospinal fluid (CSF)-circulates around brain ventricles
- Intracellular fluid -within brain cells.
The barrier located in the cerebral endothelia that separates the systemic circulation from the ISF compartment is the blood-brain barrier.
The barrier in the choroidal epithelia that separates the systemic circulation from the CSF compartment is known as the blood-CSF barrier. cont… 5 BARRIERS TO CNS DRUG DELIVERY : Blood-brain barrier ( BBB )
Blood-CSF barrier ( BCSFB )
Blood-tumor barrier ( BTB )
Main approaches toward CNS drug delivery
-Injection into CSF
-Injection directly into brain
New and effective treatments for CNS diseases must concentrate not only on the drug target within the CNS but also on the efficient delivery of the molecule to the site of action within the brain. BARRIERS TO CNS DRUG DELIVERY 6 BLOOD BRAIN BARRIER : BLOOD BRAIN BARRIER 7 which impedes and regulates the influx of most compounds from blood to brain.
Formed by brain microvascular endothelial cells (BMEC), astrocyte end feet and pericytes.
Essential for normal function of CNS.
Regulates passage of molecules in and out of brain to maintain neural environment.
Responsible for metabolic activities such as the metabolism of L-dopa to regulate its concentration in the brain. FUNCTION AND PROPERTIES OF THE BBB : FUNCTION AND PROPERTIES OF THE BBB 8 The BBB has several imp functions:
Protects the brain from “foreign substances”.
Protects the brain from hormones and neurotransmitters in the rest of body.
Maintains a constant environment for the brain.
Properties of the BBB
Large molecules do not pass through the BBB easily.
Hydrophilic molecules do not penetrate into the brain. Whereas, lipophilic molecules penetrate rapidly. Slide 9: BLOOD BRAIN BARRIER 9 Slide 10: 10 Slide 11: Diagram of a cerebral capillary enclosed in astrocyte end-feet. Characteristics of the blood-brain barrier are indicated: (1) tight junctions that seal the pathway between the capillary (endothelial) cells; (2) the lipid nature of the cell membranes of the capillary wall which makes it a barrier towater-soluble molecules; (3), (4), and (5) represent some of the carriers and ion channels; (6) the 'enzymatic barrier'that removes molecules from the blood; (7) the efflux pumps which extrude fat-soluble molecules that have crossed into the cells 11 Slide 12: 12 Slide 13: FACTORS AFFECTING DRUG PERMEATION THROUGH BBB Plasma concentration and distribution process.
Permeability of BBB to the agent
Cerebral blood flow
Route of administration
Pharmacokinetic characteristics :
Metabolism 13 TRANSPORT AT THE BBB : TRANSPORT AT THE BBB 14 Transport mechanism operating at the BBB for the peptides and proteins can be classified into the following categories:
Carrier mediated Transport system
Receptor mediated transcytosis (RMT)
Absorptive mediated transcytosis (AMT) Slide 15: 15 Slide 16: STRATEGIES FOR ENHANCED BRAIN DRUG DELIVERY 16 Slide 17: 17 Slide 18: Lipophilic analogue
Drug’s lipophilicity correlates so strongly with cerebro-vascular permeability.
Immunoliposomes (antibody-directed liposome) have been recognized as a promising tool for the site-specific delivery of drugs.
To avoid very rapid clearance of immunoliposomes, gangliosides or PEG- derivatized lipids are inserted within the bilayer.
PEG coating is believed to prevent recognition of liposomes by macrophages due to reduced binding of plasma proteins. DRUG MANIPULATION 18 Slide 19: Attach a cell-specific ligand , folic acid and monoclonal antibodies to target liposome to cells in tissue culture and organs.
Receptor specific monoclonal antibodies (mAbs) undergo receptor-mediated transcytosis through the BBB.
The mAb used in these studies is the OX26 mAb to the rat transferrin receptor, which is abundant on brain micro vascular endothelium. 19 2. Colloidal drug carrier : 2. Colloidal drug carrier 20 Micelles :
Liposomes : Slide 21: 3. Prodrug
Result from transient chemical modifications of biologically active species.
It gets converted to the active form, usually via a single activating step
CNS prodrugs is coupling the drug to a lipid moiety, such as fatty acid, glyceride or phospholipids
Such prodrug approaches were explored for a variety of acid-containing drugs, like levodopa, GABA, Niflumic acid, valproate or vigabatrin 21 4. Chemical drug delivery system : 4. Chemical drug delivery system 22 Drug delivery into CNS is by molecular packaging and sequential metabolism.
Lpf: lipophilic groups including a lipoidal T: targetor1,4-dihydropyridine
(T+): pyridinium moiety (S): A spacer function controls the enzymatic rate of drug release. Slide 23: 5. Carrier Mediated Drug Delivery
The hexose transport system for glucose and mannose.
The acidic amino acid transport system for glutamate and aspartate.
The basic amino acid transport system for arginine and lysine.
The b-amino acid transport system for b-alanine and taurine.
The choline transport system for choline and thiamine.
the amine transport system for mepyramine 23 6. Receptor mediated drug delivery system : 6. Receptor mediated drug delivery system 24 a) Chimeric peptide technology :
Present on the brain capillary endothelium
Mediate the transcytosis of the circulating peptide through the BBB
Undergo endosomal release following receptor-mediated endocytosis into the target brain cell Receptor-Associated Protein (RAP) : Receptor-Associated Protein (RAP) 25 37kDa human protein RAP has a normal function in receptor biosynthesis for lipoprotein receptor synthesis Binds to lipoprotein receptors on cell surfaces Lipoprotein receptors are the therapeutic targets for RAP Selected Members of Lipoprotein Receptor Family : Nature Cell Biology October 1999 volume 1 issue 6 pp E157-E162 DOI:10.1038/14109 Selected Members of Lipoprotein Receptor Family 26 Receptors on the BBB How Does RAP Deliver Drugs to the Brain? : How Does RAP Deliver Drugs to the Brain? 27 Blood Brain Barrier RAP receptor Brain Blood Slide 28: Osmotic blood brain barrier
Intracarotid injection of an inert hypertonic solution such as mannitol or arabinose has been employed to initiate endothelial cell shrinkage
Only a 25% increase in the permeability of the tumor microvasculature, in contrast to a 10-fold increase in the permeability of normal brain endothelium
The risk factors include the passage of plasma proteins, the altered glucose uptake, and the expression of heat shock proteins, micro embolism or abnormal neuronal function. DISRUPTION OF BBB 28 Slide 29: 2.Biochemical Blood-Brain Barrier Disruption
Selective opening of brain tumor capillaries by the intracarotid infusion of leukotriene was achieved without concomitant alteration of the adjacent BBB.
In contrast to osmotic disruption methods, biochemical opening utilizes the observation that normal brain capillaries appear to be unaffected when vasoactive leukotriene treatments are used to increase their permeability 29 Slide 30: 30 ALTERNATIVE ROUTES TO BRAIN : ALTERNATIVE ROUTES TO BRAIN 31 Olfactory and trigeminal pathway
neural pathway between nasal mucosa and brain is unique pathway for noninvasive drug delivery
a) The Olfactory neural pathway
b) The trigeminal neural pathway Intra neuronal
Axonal transport extra neuronal
Bulk transport Slide 32: Intraventricular / intrathecal delivery
Drugs can be infused using Ommaya reservoir implanted subcutaneously in the scalp
Connected to ventricles via outlet catheter
Drug solutions injected into reservoir
Delivered to the ventricles by manual compression of the reservoir
C. Interstitial delivery
Injection , catheters and pumps
Biodegradable polymer , microspheres and nanoparticals 32 Slide 33: 33 Biotechnological approaches
Implanting a tissue into the brain that naturally secretes a desired therapeutic agent.
Ex: Transplantation of embryonic dopamine-releasing neurons.
E. Transcranial route of drug delivery
Transfer of drug molecules across the cranium through the layers arteries and veins of the skin of the head.
Ex: Diazepam. MARKETED FORMULATIONS: : 34 MARKETED FORMULATIONS: Category: hypnotics Category: Anti-convulsant Category: Anti-epileptic Category: Anti-psychotic &
Anti-manic Slide 35: 35 Category: G. Anesthetic Category: sedative Category: Anti-psychotic Category: opoid CONCLUSION : CONCLUSION 36 Recent developments in drug delivery techniques provide reasonable hope that the formidable barriers shielding the brain may ultimately be overcome. REFERENCES: : Jain N. K., Controlled & Novel Drug Delivery, CBS Publishers, 256-281
Anya M. Hillary, Andrew W. Lloyd, James Swarbrick, Drug Delivery And Targetting, CRC, 1ST Indian Edition, 2010, 355-370.
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Charman W.N., Chan H.-K.,Finnin B.C. andCharman S.A., Drug Delivery: A Key Factor in Realising the Full Therapeutic Potential of Drugs , Drug Development Research, 1999,46, 316- 27 . REFERENCES: 37 Slide 38: 7. Santinijr, J.T., Richards A.C.,Scheidt R.,Cima M.J. and Langer R., Microchips as Controlled Drug-Delivery Devices ,Angew. Chem. Ed., 2000, 39, 2396-2407.
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Hiremarh S. R., Textbook of Industrial Pharmacy, Orient Longman Pvt Ltd, 91- 96,97-142 38 Slide 39: 39 Thank you…