Routes of Drug Administration. Parenteral Route

Text:Routes of Drug Administration. Parenteral Route


Grammar: Review


. Active Vocabulary


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II. Read the following text.

Routes of Drug Administration. Parenteral Route

A route of administration in pharmacology and toxicology is the path by which a drug, fluid, poison, or other substance is taken into the body.

Routes of administration are usually classified by application location. The route or course the active substance takes from application location to the location where it has its target effect is usually rather a matter of pharmacokinetics (concerning the processes of uptake, distribution, and elimination of drugs). The location of the target effect of active substances is usually rather a matter of pharmacodynamics (concerning e.g. the physiological effects of drugs). Furthermore, there is also a classification of routes of administration that basically distinguishes whether the effect is local (in topical administration) or systemic (in enteral or parenteral administration).

To obtain a general effect, the drug is usually given by oral or parenteral route. The choice depends on the drug i.e. the existence of preparations appropriate for these uses and on the state of the patient. Emergency or the impossibility of intake by mouth makes the parenteral route necessary.

To obtain a local effect, special preparations like the ophthalmic solutions may be used, but it should be remembered that a systemic diffusion is always possible after local administration.

Parenteral route. A drug to be injected by parenteral route must be sterile and little irritant. The injection requires a syringe and a needle or a device of administration already set up. One distinguishes:

Intradermal route is especially used for intradermal reactions.

Subcutaneous route. The volume of fluid injected is limited and the rate of resorption variable, depending on local factors: sclerosis, circulatory state (vasodilation, vasoconstriction). Heparin and insulin are among the drugs generally administered by subcutaneous route.

Intramuscular route. The rate of resorption is fast and it is possible to inject aqueous or oily solutions. The intramuscular injection should not be made in a vessel, nor in contact with a nerve. It is contra-indicated if the patient is undergoing anticoagulant therapy.

Intravenous route. There are two possibilities: direct injection with the syringe or administration by perfusion.

The bioavailability is by definition 100%; it is necessary however to pay attention to the speed of administration because it should not be: too rapid (which can be the case with direct administration by a syringe, with risk of severe reactions) or too slow (as observed during certain perfusions, because if the rate of elimination is rapid, the effective therapeutic concentration cannot be reached).

There are implantable devices for intravenous administration, set up surgically and used for long courses, in particular for chemotherapy.

Intra-arterial route is little used, some examples of intra-arterial administration: a vasodilator for arteritis, a thrombolytic to dissolve a clot, an antineoplastic for localized treatment of a cancer.

Intra-osseous infusion (into the bone marrow) is, in effect, an indirect intravenous access because the bone marrow drains directly into the venous system. This route is occasionally used for drugs and fluids in emergency medicine and pediatrics when intravenous access is difficult.

Routes of particular local injections. They are used to introduce a drug for diagnosis or treatment purposes in particular anatomical sites, for examples by intraspinal, intra-articular, intrapleural, intraperitoneal injections.

Answer the following questions on the text.

1. What is a route of administration in pharmacology and toxicology?

2. How are routes of drug administration classified?

3. What routes is the drug given by to obtain a general effect?

4. What is intradermal route used for?

5. Should intramuscular injection be made in a vessel?

6. Why is it necessary to pay attention to the speed of intravenous drug administration?

7. What examples of intra-arterial route do you know?

8. What is called an intra-osseous infusion?

9. What routes of particular local injections do you know?


III. Vocabulary and Speech Exercises

I. Give English equivalents of the following words and word-combinations.

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II. Explain the meaning of the following words and word-combinations.

Pharmacology; toxicology; pharmacokinetics; pharmacodynamics; physiological effect; systemic effect; emergency; ophthalmic solution; circulatory state; vasodilation; intra-arterial; pediatrics; intraspinal; intrapleural.


III. Form synonymous pairs from the words given below.

Route, poison, aqueous, fluid, emergency, rate, variable, fast, oily, clot, cancer, to drain, difficult, purpose, location.

Toxin, speed, urgency, rapid, changeable, fatty, thrombus, malignant tumour, liquid, aim, site, watery, path, hard, to flow.


IV. Discuss pros and cons of the parenteral route of drug administration.

The most common injections are intravenous (IV), intramuscular (IM), and subcutaneous (subcut).


o Fast: 15-30 seconds for IV, 3-5 minutes for IM and subcut;

o 100% bioavailability;

o Suitable for drugs not absorbed by the gut or those that are too irritant (anti-cancer);

o One injection can be formulated to last days or even months (Depo-Provera, a birth control shot that works for three months);

o IV can deliver continuous medication (morphine for patients in continuous pain, or saline drip for people needing fluids).


o Onset of action is quick, hence more risk of addiction when it comes to injecting drugs of abuse;

o Patients are not typically able to self-administer;

o Belonephobia, the fear of needles and injection;

o If needles are shared, there is risk of HIV and other infectious diseases;

o It is the most dangerous route of administration because it bypasses most of the bodys natural defenses, exposing the user to health problems such as hepatitis, abscesses, infections, and undissolved particles or additives/contaminants;

o If not done properly, potentially fatal air boluses (bubbles) can occur;

o Need for strict asepsis.


V. Memorize the meaning of the following prefix.

intra-[Intrq] prefix of Latin origin denoting within,inside

VI. Skim the text once more looking for the words having the prefixintra- in their structure. Give their definitions.

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