Absorption and  Pharmacokinetics

Pharmacy

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  • Created by: natalie
  • Created on: 17-03-14 20:24
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  • Absorption  Pharmacokinetics
    • Right dose, form, route and time
    • Routes by which solutes cross cell mem
      • Carrier mediated transport
        • Facilitated Diffusion- no atp
        • examples:- ABC(atp binding casette transporter)
          • examples:- SLC (solute carrier transporter)
      • routes of administration
        • enteral routes
          • oral
          • sublingual/buccal
          • rectal
        • parenteral routes
          • intramuscular IM
          • intravenous IV
            • 100% Bioavailability
              • =Biovalability
                • F= auc ORAL/ auc IV
                • 'F' affected by :
                  • drug formulaion
                  • first pass effect
                    • first pass effect/ bioavailabilty
                  • hepatic disease
          • inhaled
          • subcutaneous SC
  • Activation of cell membrane receptors
    • Routes by which solutes cross cell mem
      • Carrier mediated transport
        • Facilitated Diffusion- no atp
        • examples:- ABC(atp binding casette transporter)
          • examples:- SLC (solute carrier transporter)
      • routes of administration
        • enteral routes
          • oral
          • sublingual/buccal
          • rectal
        • parenteral routes
          • intramuscular IM
          • intravenous IV
            • 100% Bioavailability
              • =Biovalability
                • F= auc ORAL/ auc IV
                • 'F' affected by :
                  • drug formulaion
                  • first pass effect
                    • first pass effect/ bioavailabilty
                  • hepatic disease
          • inhaled
          • subcutaneous SC
  • Pinocytosis
    • Diffusion through (aq) channel/pore
      • Drug= non ionised and low MW
        • Diffusion through (aq) channel/pore
        • permeability coefficient: num of molecules crossing mem
          • Diffusion through lipid bilayer
            • Drug: lipid soluble
            • Partition coefficient: solubility in mem
            • Diffusion coefficient: diffusivity
        • pH and ionisation
          • Most drugs weak acid or base
            • WEAK BASES: BH+ ------- B + H+
              • protonated BH+ ionised= cannot cross cell mem but B can
            • WEAK ACIDS: HA---------- A- + H+
              • protonated HA = non ionised = can cross cell mem
          • Absorption  Pharmacokinetics
            • Right dose, form, route and time
        • WEAK BASES: BH+ ------- B + H+
          • protonated BH+ ionised= cannot cross cell mem but B can
        • Barriers to absorption
          • GI tract
          • renal tubule
        • BBB
          • Barriers to absorption
            • GI tract
            • renal tubule
        • Factors affecting rate and extent of absorption from GI tract
          • gastric emptying time
          • vomiting/diarrhoea
        • blood supply
          • Factors affecting rate and extent of absorption from GI tract
            • gastric emptying time
            • vomiting/diarrhoea
        • food in gut
          • co-administered with other drugs
            • gut lumen
              • metabolism in ;
                • liver
                • gut wall
            • First pass effect: extent of metabolism occuring before drug reaches systemic circulation
              • metabolism in ;
                • liver
                • gut wall
              • 1) drug taken orally
                • 2) absorbed from GI tract into portal circulation
                  • 3) metabolised in liver
            • 1) drug taken orally
              • 2) absorbed from GI tract into portal circulation
                • 3) metabolised in liver
            • ' F' : fraction of drug that enters systemic circulation
              • better blood supply greater rate of absorption
                • blood supply
                • only unionised forms can be absorbed in his enviro

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