II. Read the following text. Other Routes of Drug Administration

Pulmonary route is a route of fast absorption avoiding the liver: drugs absorbed by the lungs, reach the left atrium and the left ventricle, and then the general circulation. The pulmonary route is used:

• for local treatment: bronchial indications but with possibility of partial absorption and general effects. The forms used are aerosols conveying drugs such as antibiotics, mucolytic, muscarinic receptor antagonists. A lot of devices like pressurized atomizers, aerosol-batchers or sprays, inhalers of dry powder are used to introduce drugs into bronchial airways.

• for general treatment: medical gases and general anaesthetics by inhalation. Oxygen, nitric oxide and nitrous oxide which are in gas form are administered naturally by pulmonary route. The anaesthetics such as fluothane, liquids easily volatile, are administered by inhalation.

The interest of the pulmonary route is to avoid intestinal and hepatic first-pass metabolism. It could be used for drugs such as heparin and insulin.

Nasal route is used:

• for local treatment with vasoconstrictive and antiallergic drugs but with possibility of absorption and general effects.

• for general treatment: the nasal route can be used for the administration of polypeptide hormones such as desmopressin.

Cutaneous or transdermal route. The permeability of the skin to drugs depends on the drug itself, in particular its liposolubility and on the vehicle in which the drug is introduced. Resorption varies with several parameters:

• localization: it is low at the level of the plant of the feet, of the palm of the hands, important at the level of armpits, of the angle of the jaw and the scrotum.

• temperature and cutaneous circulation: if the temperature is high, there is a vasodilation which facilitates absorption.

• state of the skin: the existence of lesions (burns, for example) increases the absorption.

• age: it decreases with the age, i.e. it is more important in the new-born baby. In addition the body area compared to the weight is more important in the new-born baby and the infant than in adults.

The cutaneous route is used for local treatments by disinfectants, antimycotics, antibiotics or glucocorticoids which can sometimes be absorbed, diffuse in the whole body and be at the origin of general effects. The severe poisonings which occurred in France in 1972 in infants following applications of talc contaminated by hexachlorophene, neurotoxic product, shows that the skin, especially in new-born babies and infants, can absorb various molecules.

The transdermal route is used for introducing drugs into the body, in particular for avoiding hepatic catabolism. There are various devices for cutaneous administration, from simple application to the use of complex transdermal devices. It is used for various drugs: hormones like estradiol and progesterone, and others such as nitroglycerin, scopolamine, fentanyl.

The cutaneous route like the pulmonary and the nasal routes avoid first-pass metabolism.

Other routes: ocular, ear and vaginal. These routes are used for local treatment but a diffusion in the body is possible, with adverse effects, for example, after prescription of ophthalmic solutions, containing beta-blockers. The drugs administered by these routes are called ophthalmic solutions for the eyes, drops for the ears, and ovules for the vagina.

Answer the following questions on the text.

1. Does the pulmonary route of drug administration avoid the liver?

2. What kind of treatment is the pulmonary route used for?

3. What devices to introduce drugs into bronchial airways do you know?

4. What drugs can be administered by inhalation?

5. Vasoconstrictive and antiallergic drugs can be used by the nasal route, can’t they?

6. Can the nasal route be used for general treatment?

7. What parameters does transdermal resorption of drugs vary with?

8. Does the permeability of the skin to drugs decrease or increase with the age?

9. What drugs may cutaneous route be used for?

10. Do the cutaneous route like the pulmonary and the nasal route avoid first-pass metabolism?

11. What other routes of drug administration do you know?