Citanest (Prilocaine)

What Is Citanest and What Is It Used For?

Citanest is an injectable local anesthetic containing prilocaine hydrochloride. It belongs to the amide-type class of local anesthetics and is used to prevent local pain during medical procedures and surgeries. The medication works by reversibly blocking nerve impulse conduction in the targeted area.

Citanest is widely used across a range of medical and surgical settings to produce regional anesthesia – a reversible loss of sensation in a defined area of the body. The active substance, prilocaine hydrochloride, works by blocking sodium channels in nerve cell membranes. This prevents the nerve from transmitting pain signals to the brain, allowing the patient to undergo procedures without feeling pain in the anesthetized area.

Prilocaine was first synthesized in 1960 and has been in clinical use since the early 1960s. It was developed as an alternative to lidocaine (lignocaine) with the advantage of lower systemic toxicity, meaning it is less likely to cause adverse effects when absorbed into the bloodstream. This property makes prilocaine particularly suitable for procedures that require larger volumes of local anesthetic, such as regional nerve blocks and infiltration anesthesia for extensive surgical areas.

The medication is available as a solution for injection in two strengths: 5 mg/ml and 20 mg/ml. The lower concentration (5 mg/ml) is typically used for procedures requiring larger volumes with lower concentrations, such as epidural anesthesia, while the higher concentration (20 mg/ml) is used for infiltration anesthesia and peripheral nerve blocks where a smaller volume with a more potent effect is required.

How does prilocaine work?

Prilocaine belongs to the amide group of local anesthetics, which also includes lidocaine, bupivacaine, and ropivacaine. These medications share a common mechanism of action: they reversibly block voltage-gated sodium channels in the neuronal cell membrane. When sodium channels are blocked, the nerve cannot depolarize, and pain signals cannot be transmitted along the nerve fiber to the brain.

The onset of action is rapid, typically occurring within 2 to 5 minutes after injection, depending on the site of administration and the technique used. The duration of anesthesia varies based on the dose, concentration, and whether a vasoconstrictor (such as felypressin) is co-administered. Without a vasoconstrictor, the duration of anesthesia from prilocaine is generally intermediate, lasting approximately 1 to 2 hours for infiltration anesthesia and longer for nerve blocks.

Prilocaine is metabolized primarily in the liver and also in the kidneys, which is unique among amide local anesthetics. This dual-organ metabolism contributes to its lower systemic toxicity, as the drug is cleared from the bloodstream more rapidly than local anesthetics metabolized by the liver alone. However, one of its metabolites, ortho-toluidine, is an oxidizing agent that can convert hemoglobin to methemoglobin, which is unable to carry oxygen effectively. This is the basis for prilocaine's unique risk of methemoglobinemia, particularly at higher doses.

Common clinical uses

Citanest is used in a wide variety of clinical settings. Common applications include:

• Dental procedures: Local anesthesia for tooth extractions, fillings, and other dental work (often combined with felypressin as a vasoconstrictor)
• Minor surgical procedures: Infiltration anesthesia for wound repair, skin biopsies, and other outpatient procedures
• Peripheral nerve blocks: Regional anesthesia for limb surgery and orthopedic procedures
• Epidural anesthesia: Used in obstetric and surgical epidurals, particularly where low systemic toxicity is advantageous
• Intravenous regional anesthesia (Bier block): Prilocaine is considered the agent of choice for this technique due to its favorable safety profile

What Should You Know Before Receiving Citanest?

Citanest must not be given to patients with known allergy to prilocaine or other amide-type local anesthetics, or to those with methemoglobinemia. Special caution is required in patients with heart disease, liver or kidney problems, severe anemia, porphyria, and in neonates under 6 months of age.

Before receiving Citanest, it is essential that your healthcare provider is fully informed about your medical history, current medications, and any known allergies. While Citanest is generally well tolerated, certain conditions and situations require special precautions or may preclude its use entirely. Understanding these factors helps ensure your safety during the procedure.

Contraindications

Citanest must not be given in the following situations:

• Allergy to prilocaine or other amide-type local anesthetics: If you have had a previous allergic reaction to prilocaine, lidocaine, bupivacaine, ropivacaine, mepivacaine, or any other amide local anesthetic, you must not receive Citanest. You should also inform your doctor if you are allergic to any of the inactive ingredients (listed in the composition section below).
• Methemoglobinemia: Patients with congenital or acquired methemoglobinemia must not receive prilocaine. Methemoglobinemia is a condition in which an abnormal form of hemoglobin (methemoglobin) accumulates in the blood, reducing the blood's ability to carry oxygen to the tissues. Since prilocaine's metabolite ortho-toluidine can cause further methemoglobin formation, the medication is absolutely contraindicated in these patients.

Warnings and precautions

Tell your doctor or nurse before receiving Citanest if any of the following apply to you:

• Heart disease: Patients with high blood pressure, heart failure, or atrioventricular (AV) block require careful monitoring. Local anesthetics can affect cardiac conduction and contractility, and patients with pre-existing cardiac conditions may be more susceptible to these effects.
• Liver or kidney problems: Since prilocaine is metabolized in both the liver and kidneys, impaired function of either organ can lead to slower drug clearance and increased risk of systemic toxicity. Lower doses may be necessary.
• Severe anemia: Patients with severe anemia may be more vulnerable to the methemoglobin-forming effects of prilocaine because they already have reduced oxygen-carrying capacity. Even a relatively small increase in methemoglobin levels can produce clinically significant symptoms in these patients.
• Elderly patients or those in poor general health: These patients may have reduced capacity to metabolize and eliminate the drug and may require lower doses.
• Porphyria: If you or a family member has been diagnosed with porphyria (a rare group of blood disorders affecting heme synthesis), inform your doctor. Local anesthetics may trigger acute attacks in susceptible individuals.

Pregnancy and breastfeeding

If you are pregnant, breastfeeding, think you may be pregnant, or are planning to have a baby, consult your doctor or nurse before receiving Citanest. Your healthcare provider will carefully evaluate the benefits and risks of using prilocaine in your specific situation.

Prilocaine, like other amide local anesthetics, crosses the placental barrier. While there is limited evidence of harm in standard clinical doses, the decision to use Citanest during pregnancy should be made on a case-by-case basis. In obstetric practice, prilocaine is used for epidural anesthesia, but fetal methemoglobinemia has been reported rarely after maternal administration, particularly with higher doses.

Small amounts of prilocaine and its metabolites may pass into breast milk. However, given the short duration of action and the clinical context in which the drug is used (single-dose administration in a healthcare setting), the risk to a breastfed infant is considered minimal. Your doctor will advise you on whether any precautions are needed regarding breastfeeding after receiving Citanest.

Driving and operating machinery

Citanest may have a mild, temporary effect on mobility and coordination, which could affect your ability to drive or operate machinery. The extent of this effect depends on the dose and site of injection. For example, anesthesia of a limb may temporarily impair fine motor skills, while dental anesthesia may cause numbness of the lip or tongue that affects speech and eating.

You should not drive or operate machinery until the effects of the anesthetic have completely worn off and you feel fully capable of doing so safely. Your healthcare provider can advise you on when it is safe to resume these activities after your procedure.

Sodium content

Citanest contains 3.1 mg sodium per milliliter (ml), which is equivalent to approximately 0.2% of the WHO's recommended maximum daily sodium intake of 2 grams for adults. Your doctor will take this into account if you are on a low-sodium diet, particularly if larger volumes are administered.

How Does Citanest Interact with Other Drugs?

Citanest can interact with other local anesthetics (additive toxicity), sulfonamide antibiotics and antimalarial drugs (increased methemoglobinemia risk), and antiarrhythmic drugs such as amiodarone (increased cardiac effects). Always inform your doctor about all medications you are taking.

Drug interactions are an important consideration with any medication, and Citanest is no exception. Prilocaine can interact with several classes of drugs, potentially increasing the risk of side effects or altering the effectiveness of either medication. It is crucial that you inform your doctor or nurse about all medications you are currently taking, have recently taken, or plan to take – including prescription drugs, over-the-counter medications, and herbal supplements.

The most clinically significant interactions with Citanest fall into two main categories: those that increase the risk of systemic local anesthetic toxicity, and those that increase the risk of methemoglobinemia. Understanding these interactions helps healthcare providers make informed decisions about dosing and monitoring.

Major interactions

The most significant drug interaction with Citanest involves other local anesthetics. When multiple local anesthetics are used during the same procedure (for example, lidocaine for initial infiltration followed by prilocaine for a nerve block), their toxic effects are additive. This means that the combined dose of all local anesthetics administered must not exceed the maximum safe dose for any single agent. Your healthcare provider will carefully calculate and monitor the total dose of local anesthetics used.

Methemoglobin-inducing drugs represent another major interaction category. Sulfonamide antibiotics (such as co-trimoxazole/sulfamethoxazole), dapsone, antimalarial drugs (such as primaquine and chloroquine), nitrates, and nitrites can all cause methemoglobin formation independently. When these drugs are combined with prilocaine, which also causes methemoglobinemia through its metabolite ortho-toluidine, the risk of clinically significant methemoglobinemia is substantially increased. If you are taking any of these medications, your doctor may choose a different local anesthetic or use a reduced dose of prilocaine with enhanced monitoring.

Minor interactions

Antiarrhythmic drugs such as amiodarone, mexiletine, and other class III antiarrhythmics can interact with prilocaine because both drug classes affect cardiac conduction. While this interaction is generally manageable in clinical practice, patients taking antiarrhythmic medications may require closer cardiac monitoring during and after the administration of Citanest.

Acetaminophen (paracetamol) at very high doses has been associated with methemoglobin formation, though this is rare at therapeutic doses. Nonetheless, patients who have recently taken large doses of acetaminophen should inform their healthcare provider before receiving Citanest.

What Is the Correct Dosage of Citanest?

Citanest dosage is individualized by a healthcare professional based on the type of procedure, the area being anesthetized, and the patient's age, weight, and physical condition. The lowest effective dose should always be used. Maximum recommended dose is 6 mg/kg body weight (approximately 400 mg for an average adult).

Citanest is always administered by a trained healthcare professional – typically a doctor, dentist, or nurse anesthetist. You will not need to determine or measure the dose yourself. The dose is carefully calculated for each individual patient based on several factors, including the type and extent of the procedure, the area of the body being anesthetized, the vascularity of the tissues, the patient's age, weight, and general health, and the desired depth and duration of anesthesia.

The fundamental principle of local anesthetic dosing is to use the lowest dose that produces the desired effect. This minimizes the risk of systemic toxicity while still ensuring adequate pain control. Your healthcare provider will select the appropriate concentration (5 mg/ml or 20 mg/ml) and volume based on the specific clinical requirements.

Overdose

Citanest overdose is unlikely to occur because the medication is administered by a healthcare professional under carefully controlled conditions. However, it is important to understand the signs and symptoms of local anesthetic toxicity, as they serve as early warning indicators that prompt immediate action.

The early signs of excessive plasma levels of prilocaine include:

• Feelings of intoxication or lightheadedness
• Numbness of the lips and around the mouth
• Numbness of the tongue
• Hearing disturbances (tinnitus or hyperacusis)
• Visual disturbances (blurred vision, difficulty focusing)

If you experience any of these symptoms during or shortly after receiving Citanest, tell your doctor immediately. Your doctor will stop the administration to prevent more serious toxicity from developing.

Severe signs of local anesthetic overdose, which occur at higher plasma concentrations, include:

• Difficulty speaking (dysarthria)
• Muscle twitching and tremors
• Seizures (convulsions)
• Loss of consciousness
• Low blood pressure (hypotension)
• Slow or irregular heartbeat (bradycardia or arrhythmias)
• Cardiac arrest (in severe cases)

What Are the Side Effects of Citanest?

The most common side effects of Citanest are low blood pressure and nausea (affecting more than 1 in 10 people). Common side effects include vomiting, dizziness, tingling, slow heartbeat, and high blood pressure. A unique risk of prilocaine is methemoglobinemia, particularly at higher doses or in susceptible individuals.

Like all medicines, Citanest can cause side effects, although not everyone will experience them. Most side effects are related to the pharmacological action of the drug and are temporary, resolving as the anesthetic wears off. The frequency and severity of side effects generally correlate with the dose administered and the site of injection.

It is important to distinguish between side effects that are expected and self-limiting, and those that require immediate medical attention. If you experience any symptoms during or after receiving Citanest that concern you, tell your doctor or nurse straight away.

Methemoglobinemia – a unique risk of prilocaine

Methemoglobinemia is a distinctive side effect that sets prilocaine apart from other amide-type local anesthetics. It occurs when prilocaine's metabolite, ortho-toluidine, oxidizes the iron in hemoglobin from its ferrous (Fe²⁺) state to the ferric (Fe³⁺) state, creating methemoglobin. Unlike normal hemoglobin, methemoglobin cannot bind oxygen effectively, reducing the blood's overall oxygen-carrying capacity.

The risk of clinically significant methemoglobinemia is dose-dependent, typically occurring when doses exceed 600 mg in adults. Mild methemoglobinemia (methemoglobin levels of 1–3%) may not produce noticeable symptoms. As levels rise, symptoms progress from cyanosis (bluish discoloration of the skin, particularly noticeable on the lips, nail beds, and earlobes) at levels around 15–20%, to headache, fatigue, dizziness, and shortness of breath at levels above 20–30%, and potentially altered consciousness and cardiovascular collapse at levels exceeding 50–70%.

Treatment for significant methemoglobinemia involves administration of methylene blue (methylthioninium chloride) intravenously, which acts as an electron carrier to reduce methemoglobin back to functional hemoglobin. Healthcare providers who administer prilocaine are trained to recognize and treat this condition.

Reporting side effects

If you experience any side effects, talk to your doctor, pharmacist, or nurse. This includes any possible side effects not listed above. You can also report side effects directly to your national medicines regulatory authority. By reporting side effects, you contribute to the ongoing monitoring of the benefit-risk balance of this medicine.

How Should Citanest Be Stored?

Citanest should be stored below 25°C and must not be frozen. It should be kept out of the sight and reach of children. The medication should not be used after the expiry date printed on the container. In practice, storage is handled by the hospital or clinic.

Citanest is a medication that is stored, handled, and administered in a healthcare setting. You will not typically need to store this medication at home. However, understanding proper storage conditions is important for ensuring the medication's quality and effectiveness.

The following storage conditions apply to Citanest:

• Temperature: Store at or below 25°C (77°F). Do not freeze the solution, as freezing can alter the physical and chemical properties of the formulation.
• Light: Protect from direct sunlight when possible, although normal indoor lighting conditions are acceptable.
• Expiry date: Do not use Citanest after the expiry date stated on the container (marked as "EXP"). The expiry date refers to the last day of the stated month.
• After opening: Once the multidose vial has been opened, any remaining solution should be used promptly or discarded according to hospital protocols. Opened vials should not be stored for future use unless in accordance with validated in-use stability data.
• Children: Keep out of sight and reach of children at all times.

Your hospital, clinic, or dental practice is responsible for ensuring that Citanest is stored correctly and that expired or opened vials are properly disposed of. Unused medication should be disposed of in accordance with local regulations for pharmaceutical waste to minimize environmental impact.

What Does Citanest Contain?

Citanest contains prilocaine hydrochloride as the active substance, available in 5 mg/ml and 20 mg/ml strengths. Inactive ingredients include sodium chloride (for isotonicity), and sodium hydroxide or hydrochloric acid (for pH adjustment). It is supplied as a clear solution in a 50 ml multidose glass vial.

Understanding the composition of any medication is important, particularly for patients with known allergies or sensitivities to specific ingredients. Citanest contains both active and inactive (excipient) ingredients, each serving a specific purpose in the formulation.

Active ingredient

The active substance in Citanest is prilocaine hydrochloride. Prilocaine (chemical name: 2-(propylamino)-o-propionotoluidide) is an amide-type local anesthetic. The hydrochloride salt form is used because it is water-soluble, which is necessary for an injectable formulation. Citanest is available in two strengths:

• Citanest 5 mg/ml: Contains 5 milligrams of prilocaine hydrochloride per milliliter of solution
• Citanest 20 mg/ml: Contains 20 milligrams of prilocaine hydrochloride per milliliter of solution

Inactive ingredients (excipients)

• Sodium chloride: Added to make the solution isotonic (having the same salt concentration as body fluids), which reduces pain and tissue irritation at the injection site.
• Sodium hydroxide and/or hydrochloric acid: Used to adjust the pH of the solution to a level that is compatible with body tissues and that ensures the stability of prilocaine in solution.
• Water for injections: The solvent that makes up the bulk of the solution.

Appearance and packaging

Citanest is a clear, colorless solution supplied in a 50 ml multidose glass vial. The solution should be inspected visually before use – it should be clear and free of particles. If the solution appears discolored or contains visible particles, it should not be used.