Transdermal Drug Delivery: Flux Calculations, Patch Components, and Enhancement Techniques

Flashcards covering flux calculation steps, Transderm-Nitro patch design, physical enhancement methods (microporation, phonophoresis, iontophoresis), and chemical enhancers (water and ethanol).

What is the formula for the total drug delivered in a flux calculation?

Total drug delivered = Flux × Time (with appropriate unit conversion, e.g., 50 μg/hr = 0.05 mg/hr).

In the example, what is the converted flux rate from 50 μg/hr to mg/hr?

0.05 mg/hr.

Over 24 hours, with a flux of 0.05 mg/hr, what is the total drug delivered?

1.2 mg.

If the initial drug in the patch is 20 mg and 1.2 mg has been delivered, how much drug remains?

18.8 mg.

What percent of the initial drug remains in the patch after delivering 1.2 mg from 20 mg?

94%.

What is the Transderm-Nitro Transdermal Therapeutic System used for?

Delivering nitroglycerin through the skin into the bloodstream for 24 hours to treat and prevent angina.

What are the main components of the Transderm-Nitro patch?

Water-resistant backing, drug reservoir, semipermeable control membrane, adhesive layer with initial priming dose, and protective peel strip.

What is the role of the adhesive layer in the Transderm-Nitro patch?

To hold the system on the skin and contain the initial priming dose of nitroglycerin for prompt release and absorption.

What is the function of the semipermeable membrane in the patch?

To control the release of the medicine precisely and predictably.

How long does the Transderm-Nitro patch deliver nitroglycerin?

24 hours.

What is microporation (microneedle) and which skin layers do the needles penetrate?

A method using tiny needles to create microchannels that penetrate the stratum corneum and epidermis without reaching nerve endings in the upper dermis.

Do microporation needles reach nerve endings in the upper dermis?

No. They avoid nerve endings in the upper dermis.

What is phonophoresis (sonophoresis) and how does it enhance delivery?

Ultrasound pulses fluidize the lipid bilayer by cavitation, increasing drug permeation through the skin.

What equipment provides the ultrasound energy in phonophoresis?

An ultrasonic transducer and power supply.

What is iontophoresis and how does it drive drugs into the skin?

Passing an electric current between an active electrode and an indifferent electrode repels the drug from the active electrode into the skin.

In iontophoresis, what are the roles of the active and indifferent electrodes?

Active electrode carries the drug; indifferent electrode completes the circuit and returns current.

What are two chemical enhancers discussed and how do they affect transdermal delivery?

Water increases stratum corneum hydration (from ~15–20% to up to ~400% of tissue dry weight); Ethanol enhances permeation by lipid extraction and/or increasing drug solubility or creating a supersaturated state as it evaporates.