5 Questions
Explain the factors affecting transdermal transport and bioavailability of drugs mentioned in the text above.
The factors affecting transdermal transport and bioavailability of drugs include drug physicochemical properties (such as partition coefficient, molecular size and shape, solubility, and melting point), applied concentration/dose, ionization, dosage form effect, and physiological factors (such as skin condition, hydration, age, body site, race, and temperature).
How does the dosage form affect transdermal transport and bioavailability of drugs?
The dosage form allows optimization and control of release at a rate adequate to provide a sufficient therapeutic dose of drug. The pH of a vehicle can affect the permeability of weakly acidic and basic molecules. For example, the permeability of weakly acidic compounds decreases in alkali vehicles. Different vehicles may affect the skin by hydration and occlusion. Waxes and oil-based vehicles such as ointments increase hydration through occlusion. Aqueous vehicles will occlude the skin less than non-aqueous systems, but their aqueous nature may increase hydration.
What are the physiological factors that affect transdermal transport and bioavailability of drugs?
Physiological factors include skin condition, skin hydration and occlusion, skin age, regional variation (body site), race, and skin temperature.
How does the physicochemical properties of drugs affect transdermal transport and bioavailability?
The physicochemical properties of drugs, such as partition coefficient, molecular size and shape, solubility, melting point, and ionization, play a significant role in determining their transdermal transport and bioavailability.
Explain the impact of skin condition on transdermal transport and bioavailability of drugs.
The condition of the skin can significantly affect transdermal transport and bioavailability of drugs. Factors such as skin hydration, occlusion, age, body site, race, and temperature can all influence the permeation of drugs through the skin barrier.
Study Notes
Factors Affecting Transdermal Transport and Bioavailability of Drugs
Dosage Form
- The type of dosage form (e.g., patch, cream, ointment) affects the rate of transdermal transport and bioavailability of drugs
- Different dosage forms can alter the concentration of the drug in the skin, affecting absorption rates
Physiological Factors
- Skin temperature affects transdermal transport, with increased temperature increasing permeability
- Skin hydration affects transdermal transport, with increased hydration increasing permeability
- Blood flow to the skin affects transdermal transport, with increased blood flow increasing absorption
- Age and health status can affect transdermal transport and bioavailability
Physicochemical Properties of Drugs
- Lipophilicity of a drug affects its ability to cross the stratum corneum, with more lipophilic drugs penetrating more easily
- Molecular weight and size affect the rate of transdermal transport, with smaller molecules penetrating more easily
- Ionization state of a drug affects its ability to cross the stratum corneum, with non-ionized forms penetrating more easily
Skin Condition
- Dermatological conditions (e.g., psoriasis, eczema) can alter the skin's barrier function, affecting transdermal transport and bioavailability
- Skin integrity (e.g., wounds, cuts) can increase permeability, affecting transdermal transport and bioavailability
- Skin conditions can alter the concentration of enzymes in the skin, affecting drug metabolism and bioavailability
Test your knowledge of the factors affecting transdermal transport and bioavailability with this quiz. Explore drug physicochemical properties, dosage form effects, and physiological factors such as skin condition, hydration, and regional variation. See how well you understand the impact of partition coefficient, molecular size, applied concentration, and other key factors on transdermal drug delivery.
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