protein binding

Protein binding of drugs:

Protein binding of drugs Ms. MONIKA SHARMA “Dr. NAWAZISH ALAM” M. Pharmacy Sem. I, Dept. Of P’ceutics, S.B.S COLLEGE OF PHARMACY, PATTI. Sunday, April 10, 2011 monika sharma

Introduction:

Introduction Bound Drug is Pharmacodynamicaly inert. Binding: Half life of drug. Bonding : Hydrogen bond, Hydrophilic bond, ionic bond, Vander Walls bond. Irreversible bonding : Covalent bonding : responsible for the Carcinogenicity or Tissue toxicity. monika sharma Sunday, April 10, 2011

Binding Of Drug:

Binding Of Drug monika sharma Sunday, April 10, 2011

A) Binding to Blood Components:

A) Binding to Blood Components Sunday, April 10, 2011 monika sharma I) Plasma Protein Binding of drug: Reversible Order : Albumin > α 1 AG > Lipoproteins > Globulins. Involves binding to : Human serum Albumin. α 1 Acid Glycoprotein, Lipoproteins, Globulins

1. Binding to HSA:

1. Binding to HSA Sunday, April 10, 2011 monika sharma Primary site: Secondary site: Bond: Hydrophobic bond.

2. Binding to Lipoproteins:

2. Binding to Lipoproteins Binding by: Hydrophobic Bond. Non- competative . Mol wt : 2-3 lacks Dalton. Binded drug dissolves in Lipid core. Lipid Core composed of : Inside: Triglycerides, cholesterol esters, Outside: Appoprotein. E.g : Acidic: Diclofenac. Neutral: Cyclosporine A Basic: Chlorpromazine. Sunday, April 10, 2011 monika sharma

3. Binding to α1 Acid Glycoprotein:

3. Binding to α 1 Acid Glycoprotein Sunday, April 10, 2011 monika sharma Binding by: Hydrophobic bonds. E.g. : Basic Drugs: Imipramine, Amytriptyline, Lidocaine. 4. Binding to Globulin Globulin Synonym Binds to: 1. α 1 Globulin Transcortine /Corticosteroid Binding globulin Steroidal drugs, Thyroxin & Cyanocobalamine. 2. α 2 Globulin Ceruloplasmine Vitamin A,D,E,K. 3. β 1 Globulin Transferine Ferrous ions 4. β 2 Globulin --- Carotinoids 5. γ Globulin --- Antigens

II )Binding To Blood Cells:

II )Binding To Blood Cells Sunday, April 10, 2011 monika sharma 40 % of Blood comprises of blood cells Majority is RBCs: 500 times more diameter as Albumin. RBC Components that binds to drug:

B) Tissue Binding Of Drug::

B) Tissue Binding Of Drug: Sunday, April 10, 2011 monika sharma Importance : 1. Apparent Vd. 2. Localization of drug at specific site : so biological half life. Factors affecting : Lipophilicity, structural feature of drug, Perfusion rate, pH difference. Binding Order : Liver > Kidney > Lungs > Muscle. Organ Binding of: 1.Liver Irreversible binding of Epoxides of Halogenated Hydrocarbon & Paracetamol. 2.Lungs Basic drugs : Imipramine, Chlorpromazine, & AntiHistaminics. 3.Kidney Metallothione protein binds to Heavy metals & results in Renal accumulation 7 toxicity. 4.Skin Chloroquine & Phenothiazine binds to Melanin.

Cont…:

Cont… Organ Binding of: 5.Eye Chloroquine & Phenothiazine also binds to Eye Melanin & results in Retinopathy. 6.Hairs Arsenicals, Chloroquine, & Phenothiazine. 7.Bones Tetracycline(yellow discoloration of teeth), Lead(replaces Ca & cause brittleness) 8.Fats Lipophilic drugs (thiopental), Pesticides (DDT) 9.Nucleic Acid Chloroquine & Quinacrin. Sunday, April 10, 2011 monika sharma

Factors Affecting Protein binding::

Factors Affecting Protein binding: A)Drug Related: 1.Physicochemical Characteristics: Lipophilicity α binding. Anionic/Acidic binds : HAS Cationic/Basic binds : AAG 2. Concentration of Drug: 3.Drug protein/tissue affinity : Digoxine Affinity to cardiac muscle. B)Protein/Tissue Related: 1.Physicochemical Characteristics : Lipophilicity α binding. 2. Concentration Sunday, April 10, 2011 monika sharma

3. Number of Binding Sites:

3. Number of Binding Sites Alb. Has more. Tamoxifen & Dicumarol binds to 1 0 & 2 0 sites of alb. Indomethacine binds to 3 site. C) Drug Interaction: 1.Competition between Drugs for binding site. D1: Displaced Drug. D2: Displacer Drug. E.g. Adm. Of Phenylbutazone to Warfarine therapy patient, result in Hemorrhagic reaction. Sunday, April 10, 2011 monika sharma D1+P D2 D2+P

2. Competition Between Drug & Normal Constituents::

2. Competition Between Drug & Normal Constituents: FFA competes with HAS. Free FFA level increased during conditions : Physiological C. (Fasting) Pathological C. (Diabetes, M.I) Pharmacological (Heparin & Caffeine adm.). Acidic Drug displaces : Bilurubine from Alb. & results in Kernictarus. 3.Allosteric Changes In Protein Molecule: By drug or its Metabolite. Allosteric Modulators: are agents responsible. E.g. Aspirins acetylating of Lysine of Alb. So modifying capacity of NSAIDS binding. Sunday, April 10, 2011 monika sharma

D) Patient Related::

D) Patient Related: 1.Age: Neonates: Low Alb. content: more free drug. Young Infants: High dose of Digoxine due to large renal clearance. Elderly: Low Alb. : so more free drug. 2.Intersubject Variability: Due to Genetic & Environmental Factors. 3. Disease State: Sunday, April 10, 2011 monika sharma Disease Influence On Plasma Proteins Binding to Acidic Basic Neutral 1.Renal failure Alb. contents No Effect No Effect 2.Hepatic failure Alb. Synthesis Normal or No Effect 3.Inflammatory states AAG level No Effect No Effect

Volume Of Distribution:

Volume Of Distribution At distribution Equilibrium : Conc. of drug in body is determined By: Vol. of Tissue in which drug is present. Different tissue have diff. conc. So Vd cannot have a true physiologic meaning. (Amount of drug in body) α ( Conc. Of drug in plasma) X α C X = Vd. C Def: Hypothetical Vol. of body fluid into which drug is dissolved or distributed. It is Apparent Vd : Because : All parts of body equilibrated with drug do not have equal conc. Sunday, April 10, 2011 monika sharma

Slide 16:

Real Vd : has direct physiological meaning, Is related to body water. Sunday, April 10, 2011 monika sharma Body fluid Volume (lit.) % of Body wt. % of TWB 1.Vascular fluid (plasma) 6 (3) 9 (4.5) 15 (7.5) 2.Extracellular fluid (excl plasma) 12 14 28 3.Intracellular fluid (excl blood cells) 24 34 57 Total Body 42 60 100

Markers used to measure Real Vd:

Markers used to measure Real Vd Physiological fluid compartment Markers used Approximate vol. 1.Plasma Evans Blue, Indocyanine Green, I-131 alb. 3 2.Erythrocytes Cr-51 2 3.Extracellular fluids Non metabolizable saccharides like Raffinose, Inuline, Mannitol, & Radio isotopes of selected ions: Na + , Cl - , Br - , So 4 2-. 15 Total body water D 2 O, HTO, Antipyrine 42 Sunday, April 10, 2011 monika sharma

References:

References D.M.Brahmankar & Sunil B.Jaiswal’s Biopharmaceutics & Pharmacokinetics A Treatise, Vallabh Prakashan, New Delhi, pg. no. 86-102. http://en.wikipedia.org/wiki/Volume_of_distribution www.pharmacy.ualberta.ca Presentation at ISPA Educational Workshop, Copenhagen. www.hucmlrc.howard.edu/pharmacology Sunday, April 10, 2011 monika sharma

Slide 19:

Q uestions C omments & 4/10/2011 vikramjit singh ,"Dr.Nawazish alam" 19