Understanding the Role of Systemic Circulation in Drug Absorption through the Skin

The systemic circulation- the drug does not have to pass all the way through the dermis to access the blood (vessels are at the surface of the dermis)

The systemic circulation refers to the part of the circulatory system responsible for transporting oxygen, nutrients, hormones, and other substances to the body’s tissues

The systemic circulation refers to the part of the circulatory system responsible for transporting oxygen, nutrients, hormones, and other substances to the body’s tissues. It involves the movement of blood through a network of blood vessels, including arteries, veins, and capillaries.

When a drug is applied to the skin, it needs to reach the bloodstream in order to have a systemic effect on the body. The skin is composed of several layers, including the outermost layer called the epidermis, followed by the dermis, and then the hypodermis. The dermis is a thicker layer that contains blood vessels, nerve endings, and other structures.

During the process of drug absorption through the skin, the drug molecules must penetrate the layers of the skin to reach the blood vessels in the dermis. However, it is important to note that the drug does not have to pass all the way through the dermis to access the blood.

The reason for this is that the dermis contains a dense network of blood vessels, including capillaries that lie close to the surface of the skin. These capillaries allow for the efficient exchange of substances between the blood and the surrounding tissues. When a drug penetrates the dermis and reaches these capillaries, it can quickly enter the bloodstream and be distributed throughout the body.

The ability of a drug to penetrate the skin and reach the blood vessels in the dermis depends on various factors such as the drug’s molecular size, lipophilicity (ability to dissolve in fat), and other physical and chemical properties. Different drugs have different abilities to cross the skin barrier, and this is an important consideration in the development of topical or transdermal drug delivery systems.

In summary, when a drug is applied to the skin, it does not have to pass all the way through the dermis to access the blood. The drug molecules can penetrate into the dermis and reach the blood vessels close to the surface of the skin, allowing for systemic circulation and distribution of the drug throughout the body.

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