Biomedical Engineering Reference
In-Depth Information
aerosols generated from a conventional pMDI (Hochrainer and Hölz, 2001),
with ―respirable fraction‖ reported to be dependent on nozzle type of the
device (Steed et al., 1997).
4.
D
EVICES
U
SED IN
N
ASAL
D
RUG
D
ELIVERY
Nasal administration of therapeutic agents aims to treat local diseases
within nasal cavity such as rhinitis, nasal congestion, or recently systemic
diseases. Drug delivery via the nasal route may offer advantages since it is
convenient and needle-free which means better patient acceptability.
Moreover, the nose provides high surface area, low metabolic activity and
large blood supply for systemic absorption of many drugs. It is also very
convenient route for patients who have nausea or vomiting and for drugs that
undergo extensive hepatic first pass metabolism when given orally. However,
it is important to bear in mind that nasal delivery also has limitations such as
rapid mucociliary clearance from the nose, necessitating formulation
optimization. Moreover, the nasal epithelium is delicate and hence may be
affected by the irritating effect of some formulations. Devices used in nasal
delivery are divided into nasal drops, nasal sprays, nasal nebulizers and novel
nasal delivery devices.
4.1. Nasal Drops
Nasal drops are the most traditionally used nasal devices, which comprise
a bottle to which a dropper with rubber teat is fitted for instillation of drug
solution into nasal cavity of patient. A large fraction of the dose is wasted to
the nasopharyngeal region with this technique, possibly offering limited drug
absorption to the systemic circulation via the nose. Dose accuracy is difficult
to control and microbial contamination owing to frequent use and opening of
the container is highly possible (Kublik and Vidgren, 1998).
4.2. Nasal Sprays
Nasal sprays rely on converting the liquid midication into a spray using
mechanical means in order to spread the formulation in th frontal non-ciliated
region of the nasal cavity where mucociliary clearance is minimal. This would
