1.Transport along the concentration difference

2. No carrier required

3. No need to consume energy

4. Non-dissociable drugs with small molecular weight, high lipid solubility, small polarity are easy to be transported

1. Transport against concentration difference

2. A carrier is required, and the carrier is differentiated and selective for drugs

3. Consume energy

4. Competitive inhibition exists

5. Has saturation phenomenon

Intravenous injection and intravenous drip directly enter the blood circulation

Subcutaneous or intramuscular injection absorbed through capillary walls

Some fat-soluble drugs are absorbed through the skin

Oral drugs are absorbed through the small intestine, and a few acidic drugs can be absorbed in the stomach

Drug physical and chemical properties

Dosage form of drug

Absorb the environment

The percentage of drug binding to plasma proteins in the blood indicates the degree of drug binding to plasma proteins

Under physiological conditions, the pH of the extracellular fluid is 7.4 and the pH of the intracellular fluid is 7.0. Weakly acidic drugs are easy to dissociate in the extracellular fluid and are difficult to enter the intracellular fluid. The opposite is true for weakly alkaline drugs.

When continuous administration of drugs reaches a dynamic equilibrium between the blood drug concentration and the concentration in the tissues, the drug concentrations in each tissue are not equal, and the blood drug concentration and the concentration in the tissues are also not equal. This is due to the different affinity of the drug to each tissue.

Organs with rich blood flow such as the liver, kidneys, brain, and lungs distribute the drug faster, while the skin, fat, etc. distribute slowly.

blood brain barrier

placental barrier

blood eye barrier

Under the catalysis of enzymes, there are four ways: oxidation, reduction, hydrolysis and combination.

Specific enzyme: a specific enzyme that metabolizes a specific chemical structural group

Non-specific enzyme: non-specific enzyme, which is the liver microsomal mixed function oxidase system, also known as liver drug enzyme or drug enzyme

Pharmaceutical enzyme inducers

drug enzyme inhibitor

Renal drug excretion mode

Characteristics of renal excretion of drugs

Factors affecting renal excretion of drugs