Drug Administration part I

Dosage Forms for Oral, Ocular, and
Nasal Applications
A medicinal agent becomes a medication
only after formulation suitable for
therapeutic use (i.e., in an appropriate
dosage form). The dosage form takes
into account the intended mode of use
and also ensures ease of handling (e.g.,
stability, precision of dosing) by patients
and physicians. Pharmaceutical
technology is concerned with the design
of suitable product formulations and
quality control.
Liquid preparations (A) may take
the form of solutions, suspensions (a
sol or mixture consisting of small water-
insoluble solid drug particles dispersed
in water), or emulsions (dispersion
of minute droplets of a liquid agent
or a drug solution in another fluid, e.g.,
oil in water). Since storage will cause
sedimentation of suspensions and separation
of emulsions, solutions are generally
preferred. In the case of poorly
watersoluble substances, solution is often
accomplished by adding ethanol (or
other solvents); thus, there are both
aqueous and alcoholic solutions. These
solutions are made available to patients
in specially designed drop bottles, enabling
single doses to be measured exactly
in terms of a defined number of
drops, the size of which depends on the
area of the drip opening at the bottle
mouth and on the viscosity and surface
tension of the solution. The advantage
of a drop solution is that the dose, that
is, the number of drops, can be precisely
adjusted to the patient‘s need. Its disadvantage
lies in the difficulty that
some patients, disabled by disease or
age, will experience in measuring a prescribed
number of drops.
When the drugs are dissolved in a
larger volume — as in the case of syrups
or mixtures — the single dose is measured
with a measuring spoon. Dosing
may also be done with the aid of a
tablespoon or teaspoon (approx. 15 and
5 ml, respectively). However, due to the
wide variation in the size of commercially
available spoons, dosing will not
be very precise. (Standardized medicinal
teaspoons and tablespoons are
available.)
Eye drops and nose drops (A) are
designed for application to the mucosal
surfaces of the eye (conjunctival sac)
and nasal cavity, respectively. In order
to prolong contact time, nasal drops are
formulated as solutions of increased
viscosity.