Administering a drug through the intravenous (IV) route involves the introduction of a drug solution directly into the blood through the vein using a syringe through a needle or a needleless port on an existing IV line or a saline lock (short venous access device). It is the best way to deliver a dose rapidly and accurately, as the drug enters directly into systemic circulation without the delay associated to absorption processes, achieving its therapeutic effect faster than by any other route.
For the same reason, this route presents a bioavailability of 100%, since the pharmaceutical active ingredient usually reaches the site of action without suffering alterations due to pre-systemic effects.
Drugs are administered as bolus (e.g., i.v. ranitidine in bleeding peptic ulcer) or as an infusion (e.g., fluids infused intravenously in dehydration). The bolus injection results in a very high concentration of drug initially in the right chambers of the heart and then lungs. Then this high concentration reaches the systemic circulation. However, in this case, the peak concentration reached by the administered drug depends highly on the rate at which the drug is injected. The i.v. infusion is a better method than the bolus administration as it avoids the
- vagueness in absorption of the drug from other sites and
- the high plasma concentration that occurs due to a bolus injection
Although for patient comfort veins of the forearms (basal and middle cephalic veins) or in the wrists (cephalic accessory and medial antebrachial) are the most common sites, IV administration can be performed in any superficial vein. In certain cases, it may be necessary to resort to a central IV route, which consists in a catheter located at the outlet of the superior vena cava (right atrium). This is required when it is not possible to channel peripheral routes, for prolonged treatments or when hypertonic solutions must be administered.
Intravenous injection has to be done under close monitoring of the patient’s vitals. Only aqueous solutions can be given (suspensions are contraindicated as they can cause embolism). Oily vehicles, drugs that cause hemolysis or precipitation should not be given through this route.
Read Also: Intramuscular Route of Drug Administration: Advantages and Disadvantages
Advantages of intravenous route of drug administration
1. Bioavailability is 100%.
2. Drug reaches the stream of blood immediately having full access to the entire body and hence, rapid action is produced rendering this route to be the most efficient in life-threatening situations.
3. Irritating and non-isotonic solutions can be administered intravenously since the intima of the vein are insensitive.
4. Drug dose titration is possible in a situation where the drug has a short duration of action and the response can be measured precisely.
5. Drugs can be delivered at a uniform rate.
6. Very large volume of infusion can be administered.
7. Hypertonic solution can be administered by intravenous route, e.g. 20% mannitol in cerebral edema.
8. By i.v. infusion, a constant plasma level of the drug can be maintained, e.g. dopamine infusion in cardiogenic shock.
9. Highly irritant drugs, e.g. anticancer drugs can be given because they get diluted in blood.
10. Drugs administered by intravenous route bypass first pass metabolism.
Disadvantages of intravenous route of drug administration
1. Pain at the site of injection.
2. Once the drug is injected, its action cannot be halted and the drug cannot be removed by various methods like forced emesis or binding of charcoal (activated) as introduction of any particulate matter or any other substance can lead to fatal embolism.
3. Extravasation of some drugs can cause injury, necrosis, and sloughing of tissues.
4. Severe adverse effect especially when organs such as liver, heart, brain are involved in toxicity.
5. Local irritation may cause phlebitis.
6. Self-medication is not possible.
7. This route has a high probability of bacterial contamination, so strict aseptic conditions are needed.
8. Depot preparations cannot be given by i.v. route.
9. IV injection may induce hemolysis and other similar conditions if the drug is administered too rapidly.
References
- Kwatra, S., Taneja, G. and Nasa, N. (2012). Alternative Routes of Drug Administration- Transdermal, Pulmonary & Parenteral. Indo Global Journal of Pharmaceutical Sciences, 2(4): 409-426
- Raj, G. and Raveendran, R. (2019). Introduction to Basics of Pharmacology and Toxicology Volume 1: General and Molecular Pharmacology: Principles of Drug Action. Springer Nature Singapore Pte Ltd.
- Talevi, A. and Quiroga, P. (2018). ADME Processes in Pharmaceutical Sciences: Dosage, Design, and Pharmacotherapy Success. Switzerland AG: Springer.
