What is nitric oxide?
Nitric oxide (NO) is a gas that expands blood vessels. It’s used in a number of important bodily processes, including nerve transmission, blood flow regulation, and immune function. Because of its effects on blood vessels, nitric oxide is used as a therapeutic drug.
The most common use for this drug is in neonatal intensive care units (NICUs). It’s often used to treat newborns who have respiratory failure due to high blood pressure in the lungs (pulmonary hypertension). Outside of this use, nitric oxide may be used “off-label” to treat acute respiratory distress syndrome (ARDS) in adults and children.
Here’s what you need to know about the nitric oxide drug classification, uses, administration, warnings, side effects, and interactions based on the latest medical information.
Indications and Uses of Nitric Oxide
Nitric oxide isn’t a cure-all, but it can be a life-saver in very specific situations. Here’s where it really shines:
Neonatal Hypoxic Respiratory Failure
This is the big one. Nitric oxide is mainly used for newborns (at least 34 weeks gestational age) who have trouble breathing because their lungs’ blood vessels are too tight, leading to low oxygen levels. Think of it as a tiny pipe cleaner for their lungs.
- How it helps: It relaxes those tight blood vessels, letting more oxygen get into the baby’s blood.
- The proof: Studies like NINOS and CINRGI have shown that it can reduce the need for more extreme measures like ECMO (a heart-lung bypass machine) and improve oxygen levels.
Off-Label Uses
Sometimes, doctors try nitric oxide for things it wasn’t originally approved for. This is called “off-label” use. Here are a couple of examples:
- Acute Respiratory Distress Syndrome (ARDS): When adults and kids have really severe lung problems and low oxygen, nitric oxide might be used as a last-ditch effort to help. The doses are usually pretty low, around 5-10 ppm.
- Prevention of Bronchopulmonary Dysplasia (BPD): BPD is a lung problem that can happen in premature babies. While it might seem like nitric oxide would help, it’s actually not recommended for preventing BPD.
Dosage and Administration
Nitric oxide is a powerful drug, and dosing has to be carefully considered. Here’s what you need to know.
Dosage Guidelines
For neonatal hypoxic respiratory failure, the starting dose is typically 20 ppm. It’s delivered via a Nitric Oxide Delivery System (NODS) that’s been cleared by the FDA.
Treatment usually lasts no more than 14 days, or until the baby can be weaned off the drug. Maintenance doses may be lowered to 5-6 ppm.
For ARDS (acute respiratory distress syndrome), studies have used doses of 5-10 ppm.
Administration Protocols
Nitric oxide is delivered by inhalation using a calibrated NODS.
It’s crucial that NO delivery systems have backup power sources in case of power outages.
During nitric oxide treatment, close monitoring of inspired nitrogen dioxide (NO2) and PaO2 levels is vital.
Doctors will also need to check methemoglobin levels periodically.
Contraindications and Warnings
Like all medications, nitric oxide isn’t right for everyone, and it carries some risks.
Contraindications
You shouldn’t take nitric oxide if:
- You’re hypersensitive to it. If you’ve ever had an allergic reaction to nitric oxide, you shouldn’t take it.
- You’re a newborn with right-to-left shunting. If a neonate’s survival depends on blood flow from the right side of the heart to the left side, nitric oxide is contraindicated.
Warnings and Precautions
Nitric oxide also comes with some warnings. Here are some things to watch out for:
- Rebound pulmonary hypertension. If you stop taking nitric oxide suddenly, your pulmonary hypertension could worsen. Your doctor should gradually reduce your dose to avoid this.
- Methemoglobinemia. This blood disorder becomes more likely the more nitric oxide you take and the longer you take it. Your doctor should monitor your methemoglobin levels 4-8 hours after you start treatment and periodically after that.
- Elevated nitrogen dioxide. Your doctor should also keep an eye on your nitrogen dioxide levels. OSHA’s limit for nitrogen dioxide exposure is 5 ppm.
- Heart failure. If you have heart failure and it gets worse, your doctor should provide supportive care.
Adverse Effects and Drug Interactions
Like all drugs, nitric oxide can cause unwanted side effects and interact with other drugs you may be taking.
Adverse Effects
The following are potential adverse effects of nitric oxide; other drugs can also have adverse effects:
Common Side Effects
- Hypotension (low blood pressure)
- Withdrawal symptoms if the drug is stopped suddenly
Serious Side Effects
- Methemoglobinemia (a blood disorder that requires monitoring)
- Pulmonary toxicity and acute lung injury
- Collapsed lung
- Blood in urine
- Hyperglycemia (high blood sugar)
- Sepsis (a life-threatening response to an infection)
- Infection
- Cellulitis (a bacterial skin infection)
- Stridor (noisy breathing)
- Intracranial hemorrhage (bleeding in the brain)
- Seizure
- Gastrointestinal hemorrhage (bleeding in the digestive tract)
Accidental Exposure
Hospital staff who are accidentally exposed to nitric oxide may experience:
- Chest discomfort
- Dizziness
- Dry throat
- Shortness of breath
- Headache
Drug Interactions
Nitric oxide can interact with other medications, so it’s important to tell your doctor about all the medications you’re taking, and to be aware of potential drug interactions.
Specific Drug Interactions
Significant interactions have been observed with medications like:
- Riociguat
- Prilocaine
- Nitric oxide donor agents
General Recommendation
To prevent drug interactions, always talk with your doctor before taking any new medications, including over-the-counter drugs, supplements, and herbal remedies.
Pharmacokinetics and Mechanism of Action
So, how exactly does nitric oxide work once it’s administered, and what happens to it in the body?
Mechanism of Action
Nitric oxide’s primary action is to cause pulmonary vasodilation, which means it relaxes the blood vessels specifically within the lungs.
It achieves this by increasing the levels of cyclic GMP (cGMP). This increase leads to the relaxation of smooth muscle tissue, which in turn widens the blood vessels. This vasodilation effect improves the matching of ventilation (air flow) and perfusion (blood flow) in the lungs. Ultimately, this leads to an increase in PaO2, which stands for the partial pressure of oxygen in arterial blood, indicating better oxygenation.
Pharmacokinetics
Once inhaled, nitric oxide is rapidly absorbed and distributed throughout the lungs.
Then, it’s metabolized into nitrite and, subsequently, nitrate. Nitrate is the main metabolite, with over 70% of the administered dose eventually excreted in the urine.
Frequently Asked Questions
What drug group is nitrous oxide?
Nitrous oxide, often called “laughing gas,” falls under the drug group of dissociative anesthetics. It has analgesic and anesthetic properties, producing feelings of euphoria and detachment.
What is the classification of nitrous oxide?
The classification of nitrous oxide depends on its use. Medically, it’s classified as an anesthetic and analgesic. Recreationally, it’s often considered an inhalant or dissociative drug due to its psychoactive effects.
What is the classification of nitrous acid?
Nitrous acid (HNO2) is classified as a weak acid and an inorganic compound. It’s primarily used in chemical synthesis and is not used as a drug.
Is nitrous oxide an opioid?
No, nitrous oxide is not an opioid. Opioids work on opioid receptors in the brain to relieve pain. Nitrous oxide works through different mechanisms, primarily affecting the central nervous system by blocking NMDA receptors and activating opioid receptors indirectly.
What is the classification of nitric oxide?
Nitric oxide (NO) is classified as a vasodilator. It’s a gas that’s naturally produced in the body. As a drug, it’s used to widen blood vessels, particularly in the lungs, to improve oxygenation. It’s also considered a free radical due to its unpaired electron.
To Conclude
Nitric oxide is a key drug for treating hypoxic respiratory failure in newborns. It may also be helpful in treating ARDS in some cases.
It’s important to monitor the delivery of nitric oxide carefully and to be aware of the possible side effects. Treatment should only be administered under the close supervision of a healthcare professional experienced in using gas mixtures and aware of all the potential dangers.
Researchers are continuing to study the benefits and risks of nitric oxide treatment in different medical settings. This work may lead to new ways of using nitric oxide to treat various diseases and conditions. As research progresses, healthcare professionals will be able to better understand the best ways to use nitric oxide therapy.