Drug Delivery and Absorption

Annotations:

• Oral Pulmonary Per Rectal Intravenous Intramuscular Trnasfermal Opthamalic Subcutaneous

Annotations:

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

Annotations:

• As usual, made up of phosphobilipid layer

1. Factors affecting drug access

   Annotations:

   • 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

   Annotations:

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

      Annotations:

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

         Annotations:

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

Annotations:

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