Action in Body, Injections, When to Dose

Vasopressin is a naturally occurring hormone produced by a part of the brain known as the hypothalamus. It serves several essential functions, including maintaining the balance of fluids in the body, normalizing blood pressure, and regulating the sleep-wake cycle. It also influences emotions and behavior like fear, anxiety, protectiveness, and love.

In medicine, a synthetic version called Vasostrict is given in emergencies to raise blood pressure in people who have gone into shock. In addition to its approved use, Vasostrict is sometimes taken off-label to treat gastrointestinal bleeding, bleeding disorders, and other medical conditions.

Vasostrict is administered by injection, typically in a hospital or clinical setting. Sometimes, people with vasopressin deficiency self-administer it.

Vasopressin Hormone Functions and Effects

Vasopressin, also known as antidiuretic hormone (ADH), has two main functions: reducing the amount of urine released by the kidneys and helping raise blood pressure.

Vasopressin is produced by the hypothalamus, the part of the brain responsible for maintaining a state of equilibrium in the body, known as homeostasis. Once made, it is stored in and secreted by the pituitary gland (also known as the “master gland”).

Vasopressin is released as needed to keep key organ systems stable and balanced. Its mechanism of action—meaning the way it acts on the body—varies by the organ system.

Regulation of Body Fluids

Vasopressin is responsible for maintaining the normal balance of fluids around cells, referred to as tonicity. If fluid levels become low, the blood will become more concentrated. In response, the pituitary gland secretes vasopressin, causing the kidneys to reabsorb water and return it to circulation.

Vasopressin does so by increasing the permeability (porousness) of renal tubules. These are millions of tiny tubes in the kidneys that filter nutrients, fluids, and other substances from your blood that your body needs to keep. The remaining fluid and waste are excreted in the form of urine.

By increasing permeability, vasopressin can return the tonicity of body fluids to normal. 

Regulation of Blood Pressure

Vasopressin is also a potent vasoconstrictor that acts on smooth muscles surrounding blood vessels, causing them to narrow (constrict).

If blood pressure suddenly drops, vasopressin released by the pituitary gland will attach to receptors on the outside of blood vessels (called V1a receptors), causing vasoconstriction. By decreasing the internal volume of blood vessels, blood pressure can rise back to normal levels.

Vasopressin also influences blood pressure by keeping the volume of water in your blood consistent. Too much water can increase the internal pressure within blood vessels, leading to high blood pressure, while too little water can have the opposite effect, leading to low blood pressure.

The modulating effect of vasopressin can help keep blood pressure from fluctuating excessively.

Effects on the Brain

Vasopressin is also a central neurotransmitter, meaning a chemical messenger that acts on the central nervous system (comprised of the brain and spinal cord). Its action on the brain is centered around a part of the hypothalamus, called the suprachiasmatic nucleus, that regulates circadian rhythms in the body.

Circadian rhythms are part of the body’s internal clock, running in the background so that biological processes occur at the correct time, day or night, to keep the body functioning. Chief among these is the body’s sleep-wake cycle.

Without circadian rhythms, the body’s ability to maintain homeostasis—including functions like sleep, appetite, digestion, body temperature, and hormone release—would be severely compromised.

Effect on Mood and Behaviors

Vasopressin also acts on parts of the brain called the prefrontal cortex (the brain’s “personality center”) and amygdala (which processes emotion), where it is thought to influence social and emotional states, including fear, anxiety, and aggression. This seems especially true in males.

Some scientists even contend that vasopressin—and a related hormone also produced by the hypothalamus called oxytocin—may be directly or indirectly involved with anxiety disorders and autism.

With that said, vasopressin is also thought to promote vigilance and protective instincts that can increase emotional bonding and social attachment. In tandem with oxytocin, which provokes feelings of contentment and security, the effect of vasopressin on social behavior is regarded by some as the biological metaphor for “love.”

Other Effects

Vasopressin is also associated with nausea and may serve to trigger the vomiting reflex (emesis) when there is a gastrointestinal illness or poisoning.

Vasopressin is also known to act on the pancreas and increase the production of insulin, the hormone that helps regulate blood sugar. Persistently high levels of vasopressin are associated with an increased risk of diabetes.

Normal vs. Abnormal Vasopressin Release 

The underproduction or overproduction of vasopressin can have serious health consequences. Chief among these is the disruption of sodium levels in the blood. Abnormally high or low sodium levels cause fluid retention and also disrupt vital functions like heart rhythms and muscle contractions.

Low Vasopressin

Large amounts of diluted urine and excessive thirst (polydipsia) are characteristic of a group of conditions formerly known as diabetes insipidus. This included “central diabetes insipidus” associated with vasopressin production and “nephrogenic diabetes insipidus” associated with vasopressin response.

Today, these conditions are respectively described as:

• Arginine vasopressin deficiency (AVD): This is when the hypothalamus or pituitary gland is damaged by a head injury, brain tumor, surgery, or other diseases or conditions, preventing the production or secretion of vasopressin.
• Arginine vasopressin resistance (AVR): This is when the kidneys do not respond to the effects of vasopressin. This may be caused by an inherited disorder or a disease or medication that makes renal tubules insensitive to vasopressin, even when there is plenty of vasopressin.

Both AVD and AVR cause excessive urination, which can lead to abnormally high blood sodium levels, known as hypernatremia. Symptoms of hyponatremia include nausea, vomiting, thirst, restlessness, muscle twitches, spasms, confusion, and, in severe cases, intracranial bleeding.

High Vasopressin

Overstimulation of the hypothalamus can lead to a condition called syndrome of inappropriate antidiuretic hormone secretion (SIADH), in which excessive amounts of vasopressin are produced, leading to decreased urination.

Many different things can cause SIADH, some of which include:

• Disorders of the brain, such as head injury, infection, or stroke
• Brain surgery in the area of the hypothalamus
• Exposure to general anesthesia
• Diseases like tuberculosis, cancer, and HIV
• Substance use disorder
• Certain drugs, including anticonvulsants, antidepressants, and chemotherapy

The overproduction of vasopressin dilutes sodium levels as excessive amounts of water are retained, leading to hyponatremia. Symptoms of hyponatremia include nausea, vomiting, headaches, loss of appetite, balance problems, mental changes, and, in severe cases, seizures and coma.

Persistently high vasopressin levels can also increase insulin production. Over time, this can reduce the body’s sensitivity to insulin, resulting in glucose intolerance and type 2 diabetes.

Complications

Certain progressive kidney and heart diseases can lead to organ damage or failure due to SIADH and the overproduction of vasopressin. These include:

• Polycystic kidney disease (PKD): This is a condition characterized by frequent urination and progressive kidney injury. To compensate for the fluid loss, the pituitary gland will release more vasopressin. However, as kidney damage mounts, the reabsorbed fluid can start to accumulate in the kidneys themselves, causing irreversible kidney damage and kidney failure.
• Congestive heart failure (CHF): This is when the heart cannot pump enough blood to service the body’s needs. To compensate for the loss of circulating blood, the body will release two to three times more vasopressin than normal. The ensuing rise in blood pressure can cause cardiomyopathy (stiffening of the heart muscle), contributing to end-stage heart failure.

When to Consider Vasopressin Injections

A synthetic version of the hormone can replicate the effects of natural vasopressin and be prescribed for different medical purposes.

The synthetic version has been taken for more than 100 years and was initially released under the brand name Pitressin. The U.S. Food and Drug Administration (FDA) has licensed it under the brand name Vasostrict.

Vasostrict has one approved use: treating vasodilatory shock. This is a form of shock, also known as distributive shock, which is characterized by excessive vasodilation (widening of blood vessels).

As with other types of shock, vasodilatory shock causes a reduction of circulating blood, which deprives organs of the oxygen they need to survive. If not treated aggressively, vasodilatory shock can lead to multi-organ failure and death.

Several types of shock fall under the umbrella of vasodilatory shock, including:

Vasostrict treats vasodilatory shock by triggering rapid vasoconstriction, quickly restoring blood pressure before permanent organ damage can occur.

Off-Label Uses

Vasostrict has many off-label uses (applications not licensed by the FDA). These include managing vasopressin deficiency and treating or preventing severe bleeding conditions.

Examples include:

Surgeons will sometimes use Vasostrict to reduce the risk of bleeding during and after surgery. This is especially true for people with bleeding disorders who lack platelets or clotting factors to stem bleeding.

Vasostrict is also sometimes used by nephrologists (kidney specialists) and endocrinologists (hormone specialists) to manage people with AVP. That said, an updated version of the drug molecule called DDVAP (desmopressin) is generally preferred as it has a longer drug half-life (12 hours versus six hours) and can also be taken as a tablet or nasal spray.

DDVAP is currently licensed to treat central diabetes insipidus, hemophilia, and von Willebrand disease.

Similarly, gastroenterologists or hepatologists (liver specialists) sometimes use Vasostrict to treat esophageal varices but tend to prefer a drug called Sandostatin (octreotide), which has fewer serious side effects.

How to Administer Vasopressin Injections

Vasostrict is typically given intravenously (into a vein) but is also sometimes delivered subcutaneously (under the skin) for the management of AVD.

The method of administration varies by the condition:

• Vasodilatory shock: Vasostrict is diluted with saline or dextrose water and delivered via an intravenous (IV) drip.
• Esophageal variceal bleeding: Vasostrict is delivered for this condition similarly to shock, albeit at a higher dose. Nitroglycerin delivered by IV is taken to help lower the risk of side effects.
• Cardiac arrest: Vasostrict is typically combined with epinephrine (adrenaline) to restart a heart that has stopped entirely.
• Bleeding disorders: To reduce the risk of bleeding during or after surgery, Vasostrict is diluted with saline and delivered by IV drip, typically at a lower dose than for shock.
• Vasopressin deficiency: Vasostrict can be self-administered with daily subcutaneous injections or given intravenously in a clinic to manage AVD. Though it’s useful in people with AVD, it is not used for those with AVR because their kidneys are nonresponsive to vasopressin.

Side Effects to Monitor 

As with all medications, Vasostrict can cause side effects, some of which may be severe. Given that the drug is frequently used in emergencies, the benefits tend to outweigh the risks. If used for the management of AVD, speak with a specialist to make an informed choice.

Side effects commonly seen with intravenous Vasostrict include:

• Headaches
• Fatigue
• Shortness of breath
• Abdominal pain
• Nausea or vomiting
• Dizziness or balance problems
• Easy bruising or nosebleeds
• Abnormally slowed breathing
• Heart palpitations
• Irregular or rapid heartbeats
• Swelling of the lower legs and feet
• Confusion or mental changes
• Skin lesions
• Seizures

In addition, people may experience temporary AVD, leading to hypernatremia. Tapering the dose after the blood pressure is normalized may help reduce the risk.

The only absolute contraindication to Vasostrict is a known severe allergy to synthetic vasopressin or chlorobutanol (a preservative used in the Vasostrict formulation).

Though Vasostrict’s effect on a fetus during pregnancy is unknown, studies suggest that it may induce uterine contractions, potentially leading to miscarriage or preterm birth. Its safety in children, nursing babies, and older adults has also not been established.

Summary

Vasopressin is a hormone that the hypothalamus produces and the pituitary gland secretes. It slows down urine output and causes blood vessels to constrict. By doing so, it can maintain the normal balance of fluids in the body, regulate blood pressure, and maintain circadian rhythm and overall homeostasis. It also influences behaviors and emotions like fear, vigilance, and love.

Vasopressin is also manufactured as an injectable drug called Vasostrict, which can treat vasodilatory shock. It can also be prescribed off-label to manage vasopressin deficiency, prevent postoperative or intraoperative bleeding, and treat bleeding disorders, esophageal variceal bleeding, or cardiac arrest.