Biomedical Engineering Reference
In-Depth Information
12
Other Routes of Protein and
Peptide Delivery: Transdermal,
Topical, Uterine, and Rectal
Bhavik Shah
1
, Naazneen Surti
2
,
Ambikanandan Misra
1
1
Pharmacy Department, TIFAC - Centre of Relevance and Excellence
in New Drug Delivery Systems, The Maharaja Sayajirao University of
Baroda, PO Box 51, Kalabhavan, Vadodara 390 001, Gujarat, India
2
Baroda College of Pharmacy, Parul Arogya Seva Mandal, Limda,
Waghodia 391 760, Gujarat, India
12.1 Transdermal Delivery of Proteins and Peptides
12.1.1 Introduction
The delivery of peptides or proteins is extremely difficult. When administered orally
in the form of solution, peptides and proteins are degraded in the gastrointestinal (GI)
tract. When consumed in a formulation that prevents their degradation, their uptake in
the gut remains more difficult and highly inefficient; even with the best currently avail-
able formulations, the total uptake efficiency does not exceed a few fractions of the
administered dose. In addition to this, hepatic first-pass metabolism always has a con-
siderable effect. These are the reasons why nearly all therapeutic peptides still have to
be introduced into the body through an injection needle, in spite of the inconvenience
of this method. Numerous attempts have therefore been made to find acceptable alter-
natives. In particular, the delivery of drugs across the skin or mucosa has attracted a
great deal of attention in recent years
[1,2]
. But due to the skin permeability barrier,
normally only a fraction of the applied drug crosses the intact mammalian skin, except
for selected low-molecular-weight molecules. The use of supporting methods such as
iontophoresis, ultrasound, or electroporation improves the situation to some extent.
12.1.2 Structure of the Skin
Skin is our outermost protective shield against detrimental environmental agents.
Consequently, it is a good permeability barrier. Human skin is about 0.5 mm thick
(ranging from 0.05 to 2 mm in different parts of body) and is composed of four main
layers: the (1) stratum corneum (SC), (2) viable epidermis, (3) dermis, and (4) sub-
cutaneous tissue. A schematic cross-section of the skin is presented in
Fig. 12.1
, with
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