Cyanokit (Hydroxocobalamin)
Antidote for the treatment of known or suspected cyanide poisoning
Quick facts about Cyanokit
Key takeaways about Cyanokit
- Life-saving antidote: Cyanokit (hydroxocobalamin) is the first-line treatment for known or suspected cyanide poisoning, including smoke inhalation from fires
- Rapid mechanism of action: Hydroxocobalamin directly binds cyanide ions in the blood, converting them to non-toxic vitamin B12 (cyanocobalamin) for renal excretion
- Temporary red discoloration: Patients will experience red discoloration of skin (up to 15 days) and urine (up to 35 days) — this is harmless and expected
- Safe in all ages: Cyanokit can be used in infants, children, adolescents, and adults, including pregnant women in emergencies
- Affects lab results: Hydroxocobalamin can interfere with blood and urine laboratory tests for several days after treatment; inform healthcare providers
What Is Cyanokit and What Is It Used For?
Cyanokit is an emergency antidote containing hydroxocobalamin, used specifically for the treatment of known or suspected cyanide poisoning in patients of all ages. It works by binding cyanide ions in the blood to form the harmless compound cyanocobalamin (vitamin B12), which is then safely excreted by the kidneys.
Cyanide is an extremely toxic chemical that can rapidly cause death by preventing cells from using oxygen. Cyanide poisoning most commonly occurs through smoke inhalation during residential or industrial fires, where hydrogen cyanide gas is produced by the combustion of synthetic materials such as plastics, wool, silk, and certain building materials. Cyanide exposure can also occur through direct ingestion, skin contact with cyanide-containing substances, or industrial exposure in settings such as metal plating, mining, and chemical manufacturing.
Hydroxocobalamin, the active substance in Cyanokit, is a form of vitamin B12 that has an exceptionally high affinity for cyanide ions. When administered intravenously, each molecule of hydroxocobalamin binds one cyanide ion, forming cyanocobalamin (the common form of vitamin B12). This chemical reaction effectively detoxifies cyanide by converting it into a non-toxic compound that the kidneys can safely eliminate from the body. This mechanism restores the ability of cells to utilize oxygen for aerobic metabolism.
Cyanokit is authorized by the European Medicines Agency (EMA) as a centrally approved medicine across the European Union. The U.S. Food and Drug Administration (FDA) has also approved hydroxocobalamin for cyanide poisoning under the same brand name. It is classified as a prescription-only medicine intended for administration by trained healthcare professionals in emergency settings, including emergency departments, intensive care units, and pre-hospital environments by ambulance services.
It is critical to understand that Cyanokit does not replace other essential supportive care measures. Treatment of cyanide poisoning must always include securing the airway, providing adequate oxygenation and hydration, cardiovascular support, and management of seizures. Decontamination measures appropriate to the route of exposure must also be implemented. Cyanokit is used alongside these interventions to directly neutralize the absorbed cyanide.
The diagnosis of cyanide poisoning is often based on clinical suspicion rather than confirmed laboratory testing, as rapid blood cyanide assays are not widely available. If cyanide poisoning is suspected — particularly in fire victims with altered consciousness, cardiovascular instability, or metabolic acidosis — immediate treatment with Cyanokit is strongly recommended without waiting for confirmatory tests.
What Should You Know Before Receiving Cyanokit?
Cyanokit is an emergency medicine with few contraindications. Because cyanide poisoning is potentially fatal, the benefits of treatment almost always outweigh the risks. However, healthcare providers should be aware of allergy history, potential effects on lab tests, and interactions with hemodialysis.
Contraindications
There are no absolute contraindications to the use of Cyanokit in a life-threatening situation. Because untreated cyanide poisoning carries an extremely high mortality rate, the potential benefit of administering hydroxocobalamin far outweighs any known risk in a genuine poisoning emergency. However, a known hypersensitivity to hydroxocobalamin or to vitamin B12 should be communicated to the treating healthcare team so they can take appropriate precautions and monitor for allergic reactions during and after the infusion.
Warnings and Precautions
Several important warnings and precautions apply to the use of Cyanokit. Healthcare providers and patients should be aware of the following:
- Red discoloration: Hydroxocobalamin causes a deep red discoloration of the skin and mucous membranes that may persist for up to 15 days. This can interfere with the clinical assessment of burn injuries, as reddened skin may be misinterpreted. All patients will also experience distinctly dark red-colored urine for the first three days after treatment, potentially lasting up to 35 days.
- Laboratory interference: The deep red color of hydroxocobalamin can significantly affect colorimetric laboratory assays. Blood and urine tests may produce falsely elevated or decreased results for several laboratory parameters. Healthcare providers should be informed about prior Cyanokit administration before ordering laboratory work.
- Hemodialysis interference: Hydroxocobalamin can cause hemodialysis machines to shut down due to its intense color. Dialysis should not be performed until the drug has been substantially eliminated from the bloodstream, which requires a minimum of 5.5 to 6.5 days.
- Renal effects: Cyanokit may cause acute kidney injury and the formation of oxalate crystals in the urine. Kidney function should be monitored following treatment, particularly in patients with pre-existing renal impairment.
- Blood pressure changes: Transient increases in blood pressure have been observed, particularly toward the end of the infusion. Blood pressure typically returns to baseline within several hours. A decrease in blood pressure and an increase in heart rate have also been reported in patients with cyanide poisoning.
If you have received Cyanokit, inform all healthcare providers before undergoing any blood tests, urine tests, burn assessments, or dialysis treatments. The red discoloration caused by hydroxocobalamin can significantly interfere with clinical assessments and laboratory results for several days to weeks after treatment.
Pregnancy and Breastfeeding
Cyanokit is intended for emergency use and may be administered during pregnancy and breastfeeding when cyanide poisoning is suspected. The life-threatening nature of cyanide poisoning means the benefit of treatment far outweighs any potential risk to the developing fetus or nursing infant. Untreated cyanide poisoning would itself pose a grave risk to both mother and child.
If you were pregnant or believe you may have been pregnant during treatment with Cyanokit, inform your doctor as soon as possible. After treatment with Cyanokit, your physician will typically recommend discontinuing breastfeeding temporarily, as hydroxocobalamin and its metabolites may pass into breast milk. Your healthcare provider will advise on when it is safe to resume breastfeeding.
How Does Cyanokit Interact with Other Drugs?
Cyanokit has known physical and chemical incompatibilities with several medications commonly used during resuscitation. It must not be mixed with or administered through the same IV line as other drugs. Blood products require a separate IV access point, preferably in the opposite arm.
Due to the emergency nature of cyanide poisoning treatment, formal drug interaction studies in the conventional sense are limited. However, significant physical and chemical incompatibilities have been identified between hydroxocobalamin and several commonly used resuscitation medications. These incompatibilities can result in precipitation, inactivation, or unpredictable chemical reactions when the substances come into contact.
Administration Precautions
The following precautions are critical when administering Cyanokit alongside other treatments:
- Separate IV lines: Cyanokit must never be administered through the same intravenous line as other medications. A dedicated IV access should be established for hydroxocobalamin infusion.
- Blood products: If whole blood, packed red blood cells, platelet concentrate, or fresh frozen plasma need to be given simultaneously with hydroxocobalamin, separate intravenous access points should be used, preferably in contralateral extremities (opposite arms).
- Compatible diluents only: Cyanokit may only be reconstituted with sodium chloride 9 mg/mL (0.9%) injection solution. If 0.9% saline is unavailable, lactated Ringer's solution or 5% glucose (dextrose) injection solution may be used as alternatives.
Known Incompatibilities
| Drug / Substance | Type of Incompatibility | Clinical Recommendation |
|---|---|---|
| Sodium thiosulfate | Chemical incompatibility | Do not mix or co-administer via same IV line; use separate IV access |
| Sodium nitrite | Chemical incompatibility | Do not mix or co-administer via same IV line; use separate IV access |
| Resuscitation drugs (various) | Physical/chemical incompatibility | Must not be given through the same IV access as hydroxocobalamin |
| Blood products | Potential interference | Administer via separate IV access, preferably in opposite arm |
| Non-approved diluents | Physical incompatibility | Use only 0.9% NaCl, lactated Ringer's, or 5% glucose for reconstitution |
When a decision is made to administer another cyanide antidote (such as sodium thiosulfate) alongside Cyanokit, these medications must not be given simultaneously through the same intravenous line. Separate IV access points and staggered administration are required. The treating physician will determine the most appropriate combination therapy based on the clinical situation and available resources.
What Is the Correct Dosage of Cyanokit?
The initial adult dose of Cyanokit is 5 g (two vials) given as an intravenous infusion over 15 minutes. For children, the initial dose is 70 mg/kg body weight up to a maximum of 5 g. A second dose may be given if clinically indicated. The maximum total dose is 10 g for adults and 140 mg/kg for children.
Cyanokit is always administered by healthcare professionals as an intravenous infusion. Each vial contains 2.5 g of hydroxocobalamin as a lyophilized powder, which must be reconstituted with 100 mL of diluent before administration. The reconstituted solution has a concentration of 25 mg/mL. The dosing strategy is based on the severity of the poisoning and the patient's clinical response.
Adults
Adult dosing
- Initial dose: 5 g (200 mL of reconstituted solution from 2 vials), administered as an intravenous infusion over 15 minutes
- Second dose: An additional 5 g may be given depending on the severity of poisoning and clinical response
- Infusion rate for second dose: 15 minutes (for extremely unstable patients) to 2 hours, based on the patient's condition
- Maximum total dose: 10 g
Children (Infants, Children, and Adolescents 0–18 years)
Pediatric dosing
- Initial dose: 70 mg/kg body weight, up to a maximum of 5 g
- Second dose: 70 mg/kg body weight, up to a maximum of 5 g, if clinically indicated
- Maximum total dose: 140 mg/kg body weight, up to a maximum of 10 g
| Body Weight (kg) | Initial Dose (g) | Volume to Infuse (mL) |
|---|---|---|
| 5 | 0.35 | 14 |
| 10 | 0.70 | 28 |
| 20 | 1.40 | 56 |
| 30 | 2.10 | 84 |
| 40 | 2.80 | 112 |
| 50 | 3.50 | 140 |
| 60 | 4.20 | 168 |
Special Populations
No dose adjustment is required for patients with renal (kidney) impairment or hepatic (liver) impairment. In the emergency context of cyanide poisoning, the standard weight-based dosing applies regardless of underlying kidney or liver function.
Preparation and Administration
Each vial of Cyanokit must be reconstituted with 100 mL of 0.9% sodium chloride (normal saline) injection using the sterile transfer spike provided in the kit. If 0.9% saline is unavailable, lactated Ringer's solution or 5% glucose solution may be used. The vial should be gently rocked or inverted for at least 30 seconds to mix — do not shake, as this may cause foaming that makes it difficult to verify dissolution. The reconstituted solution is a dark red liquid and must be administered through the IV infusion set included in the kit, which contains an appropriate in-line filter.
Overdose
Limited data are available regarding overdose of hydroxocobalamin. In clinical use, doses up to 15 g have been administered without unexpected serious adverse effects beyond those described for standard therapeutic doses. Management of overdose is supportive, focusing on monitoring renal function and managing blood pressure changes. Hemodialysis may assist in clearing hydroxocobalamin from the body, but cannot be initiated until at least 5.5 to 6.5 days after treatment due to the risk of machine shutdown.
What Are the Side Effects of Cyanokit?
The most predictable effects of Cyanokit include temporary red discoloration of the skin and urine, which occurs in virtually all patients. Other possible side effects include blood pressure changes, headache, nausea, skin eruptions, and allergic reactions. The frequency of many side effects cannot be precisely estimated from available data.
Like all medicines, Cyanokit can cause side effects, although not everybody gets them. It is important to note that because Cyanokit is used in life-threatening emergencies, many of the observed effects may be related to the cyanide poisoning itself rather than the medication. The following side effects have been reported; their exact frequency cannot be calculated from the available clinical data.
Skin and Urine Discoloration
- Dark red discoloration of urine for 1–3 days (may persist up to 35 days)
- Red discoloration of skin and mucous membranes (may persist up to 15 days)
- Red-colored plasma (may affect laboratory test readings)
Heart and Blood Pressure Problems
- Increased blood pressure (particularly at the end of infusion, usually resolves within hours)
- Decreased blood pressure (also related to cyanide poisoning itself)
- Increased heart rate (tachycardia)
- Irregular heartbeat
- Facial flushing (hot flushes)
Skin Reactions
- Pustular rash (blister-like eruptions), mainly on face and neck — may persist for several weeks
- Inflammation at the infusion site
Gastrointestinal Problems
- Nausea
- Vomiting
- Diarrhea
- Stomach discomfort and indigestion
- Difficulty swallowing (dysphagia)
Allergic Reactions (Hypersensitivity)
- Swelling around the eyes, lips, tongue, throat, or hands (angioedema)
- Breathing difficulties, hoarseness, or difficulty speaking
- Skin redness, hives (urticaria), or itching
Respiratory and Chest Problems
- Pleural effusion (fluid in the chest cavity)
- Breathing difficulties (dyspnea)
- Tightness in the throat
- Dry throat
- Chest tightness
Kidney and Urinary Problems
- Acute kidney injury (renal impairment)
- Crystals in urine (crystalluria)
Other Side Effects
- Headache
- Dizziness
- Memory problems
- Restlessness
- Eye swelling, irritation, and redness
- Swollen ankles (peripheral edema)
- Changes in white blood cell counts (lymphocytes)
Swelling of the face, lips, tongue, or throat; difficulty breathing or speaking; widespread hives or severe itching. These may be signs of a serious allergic reaction requiring urgent treatment. In practice, because Cyanokit is administered in a medical facility during an emergency, healthcare providers will already be monitoring for these reactions.
The red discoloration of urine and skin is a normal and expected effect of hydroxocobalamin and does not indicate a medical problem. It occurs because of the natural deep red color of the compound. Patients should be reassured that this effect is temporary and harmless, even though the appearance can be alarming. Urine discoloration is typically most pronounced during the first three days and gradually fades.
How Should You Store Cyanokit?
Cyanokit should be stored at or below 25°C (77°F) and kept out of the reach of children. For ambulance and field use, it can withstand short-term temperature variations during transport. The reconstituted solution should be used immediately or within 6 hours if stored at 2–8°C.
Proper storage of Cyanokit is essential to maintain the efficacy and safety of the medication. The following storage guidelines apply to both hospital pharmacy settings and pre-hospital emergency services:
- Temperature: Store at or below 25°C (77°F)
- Light and moisture: Keep the vials in the original carton to protect from light
- Expiry date: Do not use after the expiration date printed on the vial, inner carton, and outer carton
- Children: Keep out of the sight and reach of children
Transport and Field Use Conditions
Because Cyanokit is frequently carried by ambulance services and emergency response teams, the product has been tested for stability under various transport conditions:
- Normal transport: 15 days at temperatures ranging from 5°C to 40°C (41°F to 104°F)
- Desert transport: 4 days at temperatures ranging from 5°C to 60°C (41°F to 140°F)
- Freeze/thaw cycles: 15 days at temperatures ranging from −20°C to 40°C (−4°F to 104°F)
Reconstituted Solution
Once reconstituted with 0.9% sodium chloride, the solution has been shown to be chemically and physically stable for up to 6 hours at temperatures between 2°C and 40°C. From a microbiological perspective, the product should be used immediately after reconstitution. If not used immediately, in-use storage times should not exceed 6 hours at 2°C to 8°C (refrigerated), and the user assumes responsibility for storage conditions.
Do not dispose of unused Cyanokit via household waste or sewage systems. Return any unused or expired kits to a pharmacy or appropriate facility for proper disposal in accordance with local regulations.
What Does Cyanokit Contain?
Each Cyanokit vial contains 2.5 g of hydroxocobalamin as the active ingredient. The only other ingredient is hydrochloric acid for pH adjustment. Each package contains two vials, sterile transfer spikes, an IV infusion set with filter, and a short catheter for pediatric administration.
Active Ingredient
The active substance is hydroxocobalamin. Each glass vial contains 2.5 g of hydroxocobalamin as a dark red, crystalline powder. When reconstituted with 100 mL of diluent, each milliliter of the resulting solution contains 25 mg of hydroxocobalamin.
Other Ingredient
The only excipient is hydrochloric acid, which is used for pH adjustment of the reconstituted solution.
Package Contents
Each Cyanokit package is designed as a complete emergency treatment kit containing:
- Two glass vials, each containing 2.5 g hydroxocobalamin powder (each vial is individually packaged in a cardboard carton)
- Two sterile transfer spikes (for reconstitution)
- One sterile intravenous infusion set with in-line filter
- One short sterile catheter for pediatric administration
The vials have bromobutyl rubber stoppers and aluminum seals with plastic caps. The complete kit provides enough medication for a full initial adult dose of 5 g (using both vials). For a second dose, an additional Cyanokit package is required.
Appearance
The hydroxocobalamin powder is dark red and crystalline in appearance. When reconstituted, it forms a dark red solution. Due to the intense color of the solution, small undissolved particles may be difficult to see visually, which is why the included IV infusion set contains a filter to catch any particulate matter.
Frequently Asked Questions About Cyanokit
Cyanokit (hydroxocobalamin) is used exclusively as an antidote for the treatment of known or suspected cyanide poisoning. Cyanide poisoning most commonly occurs from smoke inhalation during fires, but can also result from industrial exposure to cyanide-containing chemicals, ingestion of certain substances, or skin contact with cyanide compounds. Cyanokit works by binding cyanide ions in the blood to form the non-toxic compound cyanocobalamin (vitamin B12), which is then eliminated by the kidneys.
Cyanokit begins working immediately upon administration as it enters the bloodstream during the 15-minute infusion. Hydroxocobalamin binds to cyanide ions on contact, and clinical improvement may be observed during or shortly after the infusion. The rapid onset of action is critical in cyanide poisoning, where cellular oxygen utilization is blocked and delays in treatment can be fatal. The first dose is typically administered over 15 minutes to provide rapid detoxification of circulating cyanide.
The red discoloration is caused by the natural deep red color of hydroxocobalamin itself. As the substance circulates through the body and is deposited in tissues, it temporarily stains the skin and mucous membranes. The kidneys excrete the compound and its metabolites, causing the urine to turn distinctly dark red. This effect is entirely harmless and temporary — skin redness typically resolves within 15 days, while urine discoloration fades within 35 days. Patients should be reassured that this is an expected and normal effect of the medication.
Yes, Cyanokit is approved for use in patients of all ages, including infants, children, and adolescents. The pediatric dose is weight-based at 70 mg/kg body weight, with a maximum of 5 g for the initial dose. A second dose of 70 mg/kg (max 5 g) may be given if needed. The maximum total dose for children is 140 mg/kg, not exceeding 10 g. The Cyanokit package includes a short sterile catheter specifically designed for pediatric administration.
Yes, Cyanokit can significantly interfere with various blood and urine laboratory tests due to its intense deep red color. The compound affects colorimetric assays, potentially producing falsely elevated or decreased readings for several laboratory parameters. This interference may persist for several days after treatment. It is essential to inform all healthcare providers that you have received Cyanokit before any laboratory testing is performed, so that results can be interpreted correctly or alternative testing methods can be used.
Cyanokit contains hydroxocobalamin, which is a precursor form of vitamin B12. While hydroxocobalamin is indeed used in much lower doses as a vitamin B12 supplement for treating B12 deficiency, Cyanokit provides it in vastly higher concentrations (5 g compared to the typical B12 supplement dose of 1 mg). At these high antidote doses, hydroxocobalamin exploits its chemical affinity for cyanide to detoxify the poison. The product of this reaction is cyanocobalamin, which is the most common form of vitamin B12 found in supplements.
References
This article is based on the following peer-reviewed sources and official medical guidelines:
- European Medicines Agency (EMA). Cyanokit — Summary of Product Characteristics (SmPC). Last updated November 2025. Available at: EMA Cyanokit EPAR.
- U.S. Food and Drug Administration (FDA). Cyanokit (hydroxocobalamin for injection) Prescribing Information. Meridian Medical Technologies / SERB.
- Borron SW, Baud FJ, Barriot P, Imbert M, Bismuth C. Prospective study of hydroxocobalamin for acute cyanide poisoning in smoke inhalation. Annals of Emergency Medicine. 2007;49(6):794–801. doi:10.1016/j.annemergmed.2007.01.026.
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- Shepherd G, Velez LI. Role of hydroxocobalamin in acute cyanide poisoning. Annals of Pharmacotherapy. 2008;42(5):661–669. doi:10.1345/aph.1K559.
- World Health Organization (WHO). Model List of Essential Medicines. 23rd List, 2023. Geneva: WHO.
- Baud FJ. Cyanide: critical issues in diagnosis and treatment. Human & Experimental Toxicology. 2007;26(3):191–201. doi:10.1177/0960327107070566.
- Hamel J. A review of acute cyanide poisoning with a treatment update. Critical Care Nurse. 2011;31(1):72–82. doi:10.4037/ccn2011799.
- British National Formulary (BNF). Hydroxocobalamin — Emergency treatment of poisoning. NICE, 2025.
- Megarbane B, Delahaye A, Goldgran-Toledano D, Baud FJ. Antidotal treatment of cyanide poisoning. Journal of the Chinese Medical Association. 2003;66(4):193–203.
Editorial Team
This article has been written and reviewed by the iMedic Medical Editorial Team, consisting of licensed physicians and pharmacists with specialist expertise in emergency medicine, clinical toxicology, and pharmacology.
iMedic Medical Editorial Team — Specialists in emergency medicine and clinical toxicology. All content is based on current EMA SmPC, FDA prescribing information, peer-reviewed research, and international clinical guidelines.
iMedic Medical Review Board — Independent panel of board-certified physicians who verify medical accuracy, evidence quality, and clinical relevance according to the GRADE framework and international standards.
Evidence standard: All medical claims in this article are supported by Level 1A evidence (systematic reviews and randomized controlled trials) or official regulatory documents (EMA SmPC, FDA prescribing information). We follow the GRADE evidence framework and adhere to WHO, EMA, and BNF guidelines.
Conflict of interest: The iMedic editorial team has no financial relationships with pharmaceutical companies. This content is entirely independent and not sponsored by any commercial entity.