Parenteral: Definition, Preparations, Types, Indications and Parental Nutrition

The choice of fluid, the amount of fluid to be infused, and the infusion rate are determined by the fluid therapy indication.

Parenteral preparations are sterile pharmaceuticals administered to the human body by injection.

The fluid therapy parenteral administration generally involves intravenous crystalloid solutions, colloidal solutions or blood products.

Fluid therapy with crystalloid solutions is used to resuscitate patients who are hypovolemic, correct the free water deficit in the case of dehydrated patients.

Replace ongoing fluid losses and meet fluid requirements for patients who cannot take fluids by mouth.

The use of colloidal solutions is now controversial.

However, colloidal solutions (such as albumin solution) may be indicated as monotherapy or in combination with crystalloid solutions in severe cases of low oncotic pressure, especially in children.

In the case of severe bleeding, the use of blood products should be considered.

All patients receiving fluid therapy should be closely monitored using a combination of clinical parameters and laboratory tests to determine the end point of fluid therapy.

When patients have problems eating or digesting food, it is sometimes necessary to provide nutrition with artificial foods, which are specially formulated to provide the proper balance of fats, proteins, sugars, vitamins, and minerals.

These artificial preparations can be administered into the intestine to be absorbed in the usual way, which is known as enteral nutrition.

Alternatively, they can be delivered into the bloodstream through a drip to bypass the gut, known as parenteral nutrition.

If the patient’s intestine cannot be used to absorb nutrients, then the nutrition must be delivered into the patient’s bloodstream, bypassing the intestine.

Parenteral preparations


Only liquid substances can be administered, the parenteral pharmaceutical preparation is liquid, or the solid substance can be diluted with a sterile liquid or solvent before being administered.

Solvents other than water should not interfere with the effectiveness and stability of the prepared solution.

However, substances can be added to increase the effectiveness of the preparation, the important thing is that the additives do not cause toxicity or adverse effects.

When parenteral solutions are to be stored in multi-dose containers, antimicrobial preservatives are added to these formulations to prevent and inhibit the growth of microorganisms in the container.

It is necessary to validate the effectiveness of such preservatives before the start of the parenteral production process.

In the event that the active ingredient tends to degrade and oxidize, antioxidant substances are added to the parenteral preparation, and packaged under vacuum, moving with nitrogen or some other inert gas.

The containers

The containers where parenteral preparations are supplied and stored are varied: vials, bottle ampoules, and plastic bags.

Containers must be made of transparent material to allow visual inspection of the parental liquid contained.

Glass has usually been the preferred material for packaging where parenteral products are stored.

Borosilicate glass is the most resistant to chemical attack. However, plastics are becoming more common, and several types are in common use.

The choice of material will depend on the composition of the parenteral product.

The standardization for the choice of materials is established by the pharmacopoeias.

These institutions are the ones that establish quality standards for active ingredients, excipients, container material, and label and storage conditions.


When injectable samples must be taken from the containers, a special type of closure is necessary to prevent the entry of any microorganism or bacteria.

The closure material should allow passage of a hypodermic needle with minimal difficulty and have the ability to reseal when the needle is withdrawn.

Devices called elastomers are widely used as closure material for bottles.

They are also used in other primary parenteral packaging such as vial caps, plungers and tip caps for pre-fill syringes, plungers and seals for cartridges, and ports for plastic bags.


To ensure that high quality, consistent with good manufacturing process, is maintained for parenteral product packaging, each final container must be individually inspected for any contaminants.


Parenteral product labels must contain the name of the parental preparation, amount of the active ingredient, storage conditions, and what diluent or solvent must be used to achieve the necessary concentration to administer the product.

The label should never cover the entire container in order to easily inspect the product.

Types of parenteral preparation

The injection

Injections are prepared by dissolving the active ingredient and other substances in water for injections to form solutions.

The solution to be injected may show sediment that can be easily dispersed by shaking the container.

The suspension should be viewed as a homogeneous mixture to deliver the same concentration of the active ingredient each time the parent solution is taken from the container.


These parenteral preparations are composed of a sterile aqueous solution with water as the continuous phase.

These preparations become isotonic with the blood and must be free of bacterial or pyrogen endotoxins.


Injection powders are sterile solid compounds that when shaken mix to form a clear solution that should be free of particles.

Concentrated solutions

Concentrated solutions to be administered via injection or intravenous infusion must be diluted with water for injections.


Implants are solid, sterile devices that are implanted into tissue, where the active ingredient will be released for a prolonged period of time.

They are stored in sterile containers individually.

Parental fluids

Crystalloid solutions

They are aqueous solutions with varying concentrations of electrolytes and are the most commonly used fluids in a hospital setting.

Crystalloids increase intravascular volume. The extent to which they do so depends on the effect on the liquid compartments.

Colloidal solutions

A colloid is a high molecular weight substance that mostly remains confined to the intravascular compartment and therefore generates oncotic pressure.

Colloidal solutions are divided into:

  • Natural colloids: albumin, fresh frozen plasma.
  • Artificial colloids: gelatins, dextrans, hydroxyethyl starch.

Blood products

Transfusion of blood products is indicated in the case of massive blood loss.

General indications for parenteral fluid therapy

Fluid resuscitation

Patients in hypovolemic shock require rapid fluid infusions in the form of fluid problems to maintain intravascular volume.

Replacement of the free water deficit

This replacement is indicated to treat dehydration and hypernatremia .

Fluid leak replacement in progress

Fluids are also indicated in the post-resuscitation phase when the patient is no longer hypovolemic, but still has ongoing abnormal fluid loss that cannot be compensated for by oral intake alone.

Some common conditions associated with an ongoing fluid leak are:

  • For burns.
  • Polyuria due to high-performance renal failure, diabetes insipidus.
  • By surgical drainage.
  • Ongoing significant gastrointestinal leakage in case of vomiting and diarrhea.

Maintenance fluid therapy

Maintenance fluids are indicated in patients who cannot take fluids by mouth.

Other indications

  • Correction of electrolyte imbalances.
  • As a solvent for intravenous drugs.

Parental nutrition

Parenteral nutrition is by definition intravenous.


There are two types of parental nutrition:

Partial parenteral nutrition

This type of nutrition provides a part of the nutritional requirements that are needed daily, and is a complement to oral intake.

Many hospitalized patients receive dextrose or amino acid solutions using this method.

Total parenteral nutrition

This type of nutrition provides all the nutritional requirements that are needed on a daily basis.

Total parenteral nutrition must be performed through a central venous catheter since total parenteral nutrition solutions are concentrated and can cause peripheral vein thrombosis.


Total parenteral nutrition may be the viable option for those patients whose gastrointestinal tract is not functional or who suffer from disorders that require complete intestinal rest, such as in the following conditions:

  • In ulcerative colitis .
  • When there is intestinal obstruction or the intestine (ileus) cannot function.
  • Pediatric gastrointestinal disorders such as congenital gastrointestinal abnormalities, prolonged diarrhea regardless of its cause.
  • Short bowel syndrome due to surgery. Where a large part of the intestine has been removed and the patient cannot absorb enough food.
  • Bowel perforations where feeding will result in worsening infections.
  • Where parts of the intestine are diseased and cannot absorb properly (functional short intestine).


Parenteral nutrition is slowly pumped into the bloodstream through a drip.

Because it can be very irritating to blood vessels, it is usually given into a large vein near the heart through a central venous line that is placed in the upper arm, chest, or neck.

The use of parenteral nutrition can sometimes result in serious problems, such as blood infections or a disorder in biochemistry.

Therefore, patients need intensive monitoring.

If the problem with bowel function is permanent or persists for a long time, some patients may be taught how to administer their own parenteral nutrition at home (home parenteral nutrition).

Many commonly used solutions can have electrolytes added according to the needs of the patient.

The solutions to be administered vary according to other disorders present and the age of the patient, as expressed below:

  • For kidney failure not treated with dialysis or for liver failure: the parental fluid must have a reduced protein content and a high percentage of essential amino acids.
  • For heart or kidney failure: the administration of the parental fluid should be in a limited volume.
  • For respiratory failure: the parent fluid should be a lipid emulsion that provides the majority of non-protein calories to minimize carbon dioxide production from carbohydrate metabolism
  • For neonates: the lowest dextrose concentrations (approximately 17 to 18%).

Because the central venous catheter must remain in place for a long time, strict sterile technique must be used during insertion and maintenance.


Complications are related to the central venous access line.

  • Sepsis.
  • Hyperglycemia or hypoglycemia.
  • Liver dysfunction
  • Hepatomegalia dolorosa.
  • Hyperammonemia.
  • Serum electrolyte and mineral abnormalities
  • The volume overload.
  • Metabolic bone disease (osteoporosis or osteomalacia).
  • Adverse reactions to lipid emulsions such as dyspnea, allergic skin reactions, nausea, headache, back pain, sweating, dizziness.
  • Gallbladder complications such as cholelithiasis, gallbladder sludge, and cholecystitis.