Drug Delivery and Absorption

Nota:

• Oral Pulmonary Per Rectal Intravenous Intramuscular Trnasfermal Opthamalic Subcutaneous

Nota:

• 1. Most Drugs are weak acid/bases 2. Most drugs are lipophilic

Nota:

• As usual, made up of phosphobilipid layer

1. Factors affecting drug access

   Nota:

   • Molecular size and shape Degree of ionisation Relative lipid solubility of the ionised and non-ionised forms Bind affinity to receptor (membrane transport) proteins Normally, uncharged ones are the ones that are usable due to the affinity to the lipophilic layer. Extracellular concentration.
2. Methods of Traversal

   Nota:

   • Pinocytosis Passive Diffusion Filtration Active Transport
   1. Passive Membrane Transport

      Nota:

      • Ionization will affect and influence solublility and hence it is dependent on Ka and local pH
      1. pH in body

         Nota:

         • Urine : 5 Small intestine : 7.8 Duodenum: 6 Saliva: 6 Stomach 1.3 Serum/blood: 7.4 CSF: 7.35
      2. Henderson-hasselbalch

Nota:

• Degree of a drug becomes available to target tissue after administration Proportion of the administered dose that reaches the systemic circulation intact