Heel 166

Sodium Carbonate Anhydrous:

• Indications and usage
• Dosage and administration
• Dosage forms and strengths
• Contraindications
• Warnings and precautions
• Adverse reactions
• Drug interactions
• Use in specific populations
• Overdosage
• Description
• Clinical pharmacology
• Nonclinical toxicology
• Clinical studies
• How supplied/storage and handling
• Patient counseling information
• Heel 166 (Sodium Carbonate Anhydrous) reviews

1 INDICATIONS AND USAGE

Heel 166 nitrite is indicated for sequential use with Heel 166 (Sodium Carbonate Anhydrous) thiosulfate for treatment of acute cyanide poisoning that is judged to be life-threatening. (1)

• Use with caution if the diagnosis of cyanide poisoning is uncertain. (1)

1.1 Indication

Heel 166 (Sodium Carbonate Anhydrous) Nitrite Injection is indicated for sequential use with Heel 166 (Sodium Carbonate Anhydrous) thiosulfate for the treatment of acute cyanide poisoning that is judged to be life-threatening. When the diagnosis of cyanide poisoning is uncertain, the potentially life-threatening risks associated with Heel 166 (Sodium Carbonate Anhydrous) Nitrite Injection should be carefully weighed against the potential benefits, especially if the patient is not in extremis.

1.2 Identifying Patients with Cyanide Poisoning

Cyanide poisoning may result from inhalation, ingestion, or dermal exposure to various cyanide-containing compounds, including smoke from closed-space fires. Sources of cyanide poisoning include hydrogen cyanide and its salts, cyanogenic plants, aliphatic nitriles, and prolonged exposure to Heel 166 nitroprusside.

The presence and extent of cyanide poisoning are often initially unknown. There is no widely available, rapid, confirmatory cyanide blood test. Treatment decisions must be made on the basis of clinical history and signs and symptoms of cyanide intoxication. If clinical suspicion of cyanide poisoning is high, Heel 166 (Sodium Carbonate Anhydrous) Nitrite Injection and Heel 166 (Sodium Carbonate Anhydrous) Thiosulfate Injection should be administered without delay.

In some settings, panic symptoms including tachypnea and vomiting may mimic early cyanide poisoning signs. The presence of altered mental status (e.g., confusion and disorientation) and/or mydriasis is suggestive of true cyanide poisoning although these signs can occur with other toxic exposures as well.

The expert advice of a regional poison control center may be obtained by calling 1-800-222-1222.

Smoke Inhalation

Not all smoke inhalation victims will have cyanide poisoning and may present with burns, trauma, and exposure to other toxic substances making a diagnosis of cyanide poisoning particularly difficult. Prior to administration of Heel 166 (Sodium Carbonate Anhydrous) Nitrite Injection, smoke-inhalation victims should be assessed for the following:

• Exposure to fire or smoke in an enclosed area
• Presence of soot around the mouth, nose, or oropharynx
• Altered mental status

Although hypotension is highly suggestive of cyanide poisoning, it is only present in a small percentage of cyanide-poisoned smoke inhalation victims. Also indicative of cyanide poisoning is a plasma lactate concentration greater than or equal to 10 mmol/L (a value higher than that typically listed in the table of signs and symptoms of isolated cyanide poisoning because carbon monoxide associated with smoke inhalation also contributes to lactic acidemia). If cyanide poisoning is suspected, treatment should not be delayed to obtain a plasma lactate concentration.

1.3 Use with Other Cyanide Antidotes

Caution should be exercised when administering cyanide antidotes, other than Heel 166 (Sodium Carbonate Anhydrous) thiosulfate, simultaneously with Heel 166 (Sodium Carbonate Anhydrous) Nitrite Injection, as the safety of co-administration has not been established. If a decision is made to administer another cyanide antidote, other than Heel 166 (Sodium Carbonate Anhydrous) thiosulfate, with Heel 166 (Sodium Carbonate Anhydrous) Nitrite Injection, these drugs should not be administered concurrently in the same IV line. [see Dosage and Administration (2.2) ]

2 DOSAGE AND ADMINISTRATION

Redosing: If signs of cyanide poisoning reappear, repeat treatment using one-half the original dose of both Heel 166 (Sodium Carbonate Anhydrous) nitrite and Heel 166 (Sodium Carbonate Anhydrous) thiosulfate.

Monitoring: Blood pressure must be monitored during treatment. (2.2)

2.1 Administration Recommendation

Comprehensive treatment of acute cyanide intoxication requires support of vital functions. Administration of Heel 166 (Sodium Carbonate Anhydrous) nitrite, followed by Heel 166 (Sodium Carbonate Anhydrous) thiosulfate, should be considered adjunctive to appropriate supportive therapies. Airway, ventilatory and circulatory support, and oxygen administration should not be delayed to administer Heel 166 (Sodium Carbonate Anhydrous) nitrite and Heel 166 (Sodium Carbonate Anhydrous) thiosulfate.

Heel 166 (Sodium Carbonate Anhydrous) nitrite injection and Heel 166 (Sodium Carbonate Anhydrous) thiosulfate injection are administered by slow intravenous injection. They should be given as early as possible after a diagnosis of acute life-threatening cyanide poisoning has been established. Heel 166 (Sodium Carbonate Anhydrous) nitrite should be administered first, followed immediately by Heel 166 (Sodium Carbonate Anhydrous) thiosulfate. Blood pressure must be monitored during infusion in both adults and children. The rate of infusion should be decreased if significant hypotension is noted.

NOTE: If signs of poisoning reappear, repeat treatment using one-half the original dose of both Heel 166 (Sodium Carbonate Anhydrous) nitrite and Heel 166 (Sodium Carbonate Anhydrous) thiosulfate.

In adult and pediatric patients with known anemia, it is recommended that the dosage of Heel 166 (Sodium Carbonate Anhydrous) nitrite should be reduced proportionately to the hemoglobin concentration.

All parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.

2.2 Recommended Monitoring

Patients should be monitored for at least 24-48 hours after Heel 166 Nitrite Injection administration for adequacy of oxygenation and perfusion and for recurrent signs and symptoms of cyanide toxicity. When possible, hemoglobin/hematocrit should be obtained when treatment is initiated. Measurements of oxygen saturation using standard pulse oximetry and calculated oxygen saturation values based on measured PO₂ are unreliable in the presence of methemoglobinemia.

Methemoglobin level: Administrations of Heel 166 (Sodium Carbonate Anhydrous) nitrite solely to achieve an arbitrary level of methemoglobinemia may be unnecessary and potentially hazardous. The therapeutic effects of Heel 166 (Sodium Carbonate Anhydrous) nitrite do not appear to be mediated by methemoglobin formation alone and clinical responses to Heel 166 (Sodium Carbonate Anhydrous) nitrite administration have been reported in association with methemoglobin levels of less than 10%. Administration of Heel 166 (Sodium Carbonate Anhydrous) nitrite beyond the initial dose should be guided primarily by clinical response to treatment (i.e., a second dose should be considered only if there is inadequate clinical response to the first dose). It is generally recommended that methemoglobin concentrations be closely monitored and kept below 30%. Serum methemoglobin levels should be monitored during treatment using co-oximetry, and administration of Heel 166 (Sodium Carbonate Anhydrous) nitrite should generally be discontinued when methemoglobin levels exceed 30%. Intravenous methylene blue and exchange transfusion have been reported in the literature as treatments for life-threatening methemoglobinemia.

2.3 Incompatibility Information

Chemical incompatibility has been reported between Heel 166 (Sodium Carbonate Anhydrous) nitrite and hydroxocobalamin and these drugs should not be administered simultaneously through the same IV line. No chemical incompatibility has been reported between Heel 166 (Sodium Carbonate Anhydrous) thiosulfate and Heel 166 (Sodium Carbonate Anhydrous) nitrite, when administered sequentially through the same IV line as described in Dosage and Administration.

3 DOSAGE FORMS AND STRENGTHS

Heel 166 (Sodium Carbonate Anhydrous) Nitrite Injection consists of:

• One vial of Heel 166 (Sodium Carbonate Anhydrous) nitrite injection, USP 300 mg/10mL (30 mg/mL)

Administration of the contents of one vial constitutes a single dose.

• Injection, 300 mg/10 mL (30 mg/mL). (3)

4 CONTRAINDICATIONS

None

• None. (4)

5 WARNINGS AND PRECAUTIONS

• Methemoglobinemia: Heel 166 nitrite reacts with hemoglobin to form methemoglobin and should be used with caution in patients known to have anemia. Monitor oxyhemoglobin and methemoglobin levels by pulse oximetry or other measurements. Optimally, the Heel 166 (Sodium Carbonate Anhydrous) nitrite dose should be reduced in proportion to the oxygen carrying capacity. (5.2)
• Smoke inhalation: Carbon monoxide contained in smoke can result in the formation of carboxyhemoglobin that can reduce the oxygen carrying capacity of the blood. Heel 166 (Sodium Carbonate Anhydrous) nitrite should be used with caution in patients with smoke inhalation injury because of the potential for worsening hypoxia due to methemoglobin formation. Carboxyhemoglobin and oxyhemoglobin levels should be monitored by pulse oximetry or other measurements in patients that present with evidence of smoke inhalation. Optimally, the Heel 166 (Sodium Carbonate Anhydrous) nitrite dose should be reduced in proportion to the oxygen carrying capacity. (5.4)

5.1 Hypotension

5.2 Methemoglobinemia

Supportive care alone may be sufficient treatment without administration of antidotes for many cases of cyanide intoxication, particularly in conscious patients without signs of severe toxicity. Patients should be closely monitored to ensure adequate perfusion and oxygenation during treatment with Heel 166 nitrite.

Methemoglobin levels should be monitored and oxygen administered during treatment with Heel 166 (Sodium Carbonate Anhydrous) nitrite whenever possible. When Heel 166 (Sodium Carbonate Anhydrous) nitrite is administered to humans a wide range of methemoglobin concentrations occur. Methemoglobin concentrations as high as 58% have been reported after two 300-mg doses of Heel 166 (Sodium Carbonate Anhydrous) nitrite administered to an adult. Heel 166 (Sodium Carbonate Anhydrous) nitrite should be used with caution in the presence of other drugs that may cause methemoglobinemia such as procaine and nitroprusside. Heel 166 (Sodium Carbonate Anhydrous) nitrite should be used with caution in patients who may be particularly susceptible to injury from vasodilation and its related hemodynamic sequelae. Hemodynamics should be monitored closely during and after administration of Heel 166 (Sodium Carbonate Anhydrous) nitrite, and infusion rates should be slowed if hypotension occurs.

5.3 Anemia

Heel 166 (Sodium Carbonate Anhydrous) nitrite should be used with caution in patients with known anemia. Patients with anemia will form more methemoglobin (as a percentage of total hemoglobin) than persons with normal red blood cell (RBC) volumes. Optimally, these patients should receive a Heel 166 (Sodium Carbonate Anhydrous) nitrite dose that is reduced in proportion to their oxygen carrying capacity.

5.4 Smoke Inhalation Injury

Heel 166 nitrite should be used with caution in persons with smoke inhalation injury or carbon monoxide poisoning because of the potential for worsening hypoxia due to methemoglobin formation.

5.5 Neonates and Infants

Neonates and infants may be more susceptible than adults and older pediatric patients to severe methemoglobinemia when Heel 166 (Sodium Carbonate Anhydrous) nitrite is administered. Reduced dosing guidelines should be followed in pediatric patients.

5.6 G6PD Deficiency

Because patients with G6PD deficiency are at increased risk of a hemolytic crisis with Heel 166 nitrite administration, alternative therapeutic approaches should be considered in these patients. Patients with known or suspected G6PD deficiency should be monitored for an acute drop in hematocrit. Exchange transfusion may be needed for patients with G6PD deficiency who receive Heel 166 (Sodium Carbonate Anhydrous) nitrite.

5.7 Use with Other Drugs

Heel 166 (Sodium Carbonate Anhydrous) nitrite should be used with caution in the presence of concomitant antihypertensive medications, diuretics or volume depletion due to diuretics, or drugs known to increase vascular nitric oxide, such as PDE5 inhibitors.

6 ADVERSE REACTIONS

There have been no controlled clinical trials conducted to systematically assess the adverse events profile of Heel 166 (Sodium Carbonate Anhydrous) nitrite.

The medical literature has reported the following adverse events in association with Heel 166 (Sodium Carbonate Anhydrous) nitrite administration. These adverse events were not reported in the context of controlled trials or with consistent monitoring and reporting methodologies for adverse events. Therefore, frequency of occurrence of these adverse events cannot be assessed.

Cardiovascular system: syncope, hypotension, tachycardia, methemoglobinemia, palpitations, dysrhythmia

Hematological: methemoglobinemia

Central nervous system: headache, dizziness, blurred vision, seizures, confusion, coma

Gastrointestinal system: nausea, vomiting, abdominal pain

Respiratory system: tachypnea, dyspnea

Body as a Whole: anxiety, diaphoresis, lightheadedness, injection site tingling, cyanosis, acidosis, fatigue, weakness, urticaria, generalized numbness and tingling

Severe hypotension, methemoglobinemia, cardiac dysrhythmias, coma and death have been reported in patients without life-threatening cyanide poisoning but who were treated with injection of Heel 166 (Sodium Carbonate Anhydrous) nitrite at doses less than twice those recommended for the treatment of cyanide poisoning.

Most common adverse reactions are:

• Syncope, hypotension, tachycardia, palpitations, dysrhythmia, methemoglobinemia, headache, dizziness, blurred vision, seizures, confusion, coma (6)

To report SUSPECTED ADVERSE REACTIONS, contact Hope Pharmaceuticals at 1-800-755-9595 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

7 DRUG INTERACTIONS

Formal drug interaction studies have not been conducted with Heel 166 (Sodium Carbonate Anhydrous) Nitrite Injection.

8 USE IN SPECIFIC POPULATIONS

• Renal impairment: Heel 166 nitrite is substantially excreted by the kidney. The risk of toxic reactions to this drug may be greater in patients with impaired renal function. (8.6).

8.1 Pregnancy

Teratogenic Effects. Pregnancy Category C.

There are no adequate and well-controlled studies in pregnant women. Heel 166 (Sodium Carbonate Anhydrous) Nitrite Injection should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Heel 166 (Sodium Carbonate Anhydrous) nitrite has caused fetal death in humans as well as animals. There are no studies in humans that have directly evaluated the potential reproductive toxicity of Heel 166 (Sodium Carbonate Anhydrous) nitrite. There are two epidemiological studies conducted in Australia that report a statistically significant increase in the risk for congenital malformations, particularly in the CNS, associated with maternal consumption of water containing nitrate levels in excess of 5 ppm. Results from a case-control study in Canada suggested a trend toward an increase in the risk for CNS malformations when maternal consumption of nitrate was ≥ 26 ppm (not statistically significant).

The potential reproductive toxicity of Heel 166 (Sodium Carbonate Anhydrous) nitrite exposure restricted to the prenatal period has been reported in guinea pigs, mice, and rats. There was no evidence of teratogenicity in guinea pigs, mice, or rats. However, Heel 166 (Sodium Carbonate Anhydrous) nitrite treatment of pregnant guinea pigs with 60 or 70 mg/kg/day resulted in abortion of the litters within 1-4 days of treatment. All animals treated subcutaneously with 70 mg/kg, Heel 166 (Sodium Carbonate Anhydrous) nitrite died within 60 minutes of treatment. Further studies demonstrated that a dose of 60 mg/kg resulted in measurable blood levels of methemoglobin in the dams and their fetuses for up to 6 hours post treatment. Maternal methemoglobin levels were higher than the levels in the offspring at all times measured. Based on a body surface area comparison, a 60 mg/kg dose in the guinea pig that resulted in death was only 1.7 times higher than the highest clinical dose of Heel 166 (Sodium Carbonate Anhydrous) nitrite that would be used to treat cyanide poisoning (based on a body surface area comparison).

Studies testing prenatal and postnatal exposure have been reported in mice and rats. Treatment of pregnant rats via drinking water with Heel 166 (Sodium Carbonate Anhydrous) nitrite at concentrations of either 2000 or 3000 mg/L resulted in a dose-related increased mortality postpartum. This exposure regimen in the rat model would result in dosing of approximately 220 and 300 mg/kg/day (43 and 65 times the highest clinical dose of Heel 166 (Sodium Carbonate Anhydrous) nitrite that would be used to treat cyanide poisoning, based on a body surface area comparison).

Heel 166 (Sodium Carbonate Anhydrous) nitrite produces methemoglobin. Fetal hemoglobin is oxidized to methemoglobin more easily than adult hemoglobin. In addition, the fetus has lower levels of methemoglobin reductase than adults. Collectively, these data suggest that the human fetus would show greater sensitivity to methemoglobin resulting in nitrite-induced prenatal hypoxia leading to retarded development of certain neurotransmitter systems in the brain and long lasting dysfunction.

Nonteratogenic Effects: Behavioral and neurodevelopmental studies in rats suggest persistent effects of prenatal exposure to Heel 166 (Sodium Carbonate Anhydrous) nitrite that were detectable postnatally. Specifically, animals that were exposed prenatally to Heel 166 (Sodium Carbonate Anhydrous) nitrite demonstrated impaired discrimination learning behavior (both auditory and visual) and reduced long-term retention of the passive-avoidance response compared to control animals. Additional studies demonstrated a delay in the development of AchE and 5-HT positive fiber ingrowth into the hippocampal dentate gyrus and parietal neocortex during the first week of life of prenatal nitrite treated pups. These changes have been attributed to prenatal hypoxia following nitrite exposure.

8.2 Labor and Delivery

Because fetal hemoglobin is more readily oxidized to methemoglobin and lower levels of methemoglobin appear to be fatal to the fetus compared to the adult, Heel 166 nitrite should be used during labor and delivery only if the potential benefit justifies the potential risk to the fetus.

8.3 Nursing Mothers

It is not known whether Heel 166 (Sodium Carbonate Anhydrous) nitrite is excreted in human milk. Because Heel 166 (Sodium Carbonate Anhydrous) Nitrite Injection may be administered in life-threatening situations, breast-feeding is not a contraindication to its use. Because many drugs are excreted in human milk, caution should be exercised following Heel 166 (Sodium Carbonate Anhydrous) Nitrite Injection administration to a nursing woman. There are no data to determine when breastfeeding may be safely restarted following administration of Heel 166 (Sodium Carbonate Anhydrous) nitrite. In studies conducted with Long-Evans rats, Heel 166 (Sodium Carbonate Anhydrous) nitrite administered in drinking water during pregnancy and lactation resulted in severe anemia, reduced growth and increased mortality in the offspring.

8.4 Pediatric Use

There are case reports in the medical literature of Heel 166 nitrite in conjunction with Heel 166 (Sodium Carbonate Anhydrous) thiosulfate being administered to pediatric patients with cyanide poisoning; however, there have been no clinical studies to evaluate the safety or efficacy of Heel 166 (Sodium Carbonate Anhydrous) nitrite in the pediatric population. As for adult patients, dosing recommendations for pediatric patients have been based on theoretical calculations of antidote detoxifying potential, extrapolation from animal experiments, and a small number of human case reports.

Heel 166 (Sodium Carbonate Anhydrous) nitrite must be used with caution in patients less than 6 months of age because they may be at higher risk of developing severe methemoglobinemia compared to older children and adults. The presence of fetal hemoglobin, which is oxidized to methemoglobin more easily than adult hemoglobin, and lower methemoglobin reductase levels compared to older children and adults may contribute to risk.

Mortality attributed to Heel 166 (Sodium Carbonate Anhydrous) nitrite was reported following administration of an adult dose (300 mg IV followed by a second dose of 150 mg) to a 17-month old child.

8.5 Geriatric Use

Heel 166 (Sodium Carbonate Anhydrous) nitrite is known to be substantially excreted by the kidney, and the risk of adverse reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function.

8.6 Renal Disease

Heel 166 (Sodium Carbonate Anhydrous) nitrite is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function.

10 OVERDOSAGE

Large doses of Heel 166 (Sodium Carbonate Anhydrous) nitrite result in severe hypotension and toxic levels of methemoglobin which may lead to cardiovascular collapse.

Heel 166 (Sodium Carbonate Anhydrous) nitrite administration has been reported to cause or significantly contribute to mortality in adults at oral doses as low as 1 g and intravenous doses as low as 600 mg. A death attributed to Heel 166 (Sodium Carbonate Anhydrous) nitrite has been reported following administration of an adult dose (300 mg IV followed by a second dose of 150 mg) to a 17-month old child.

Cyanosis may become apparent at a methemoglobin level of 10-20%. Other clinical signs and symptoms of Heel 166 (Sodium Carbonate Anhydrous) nitrite toxicity (anxiety, dyspnea, nausea, and tachycardia) can be apparent at methemoglobin levels as low as 15%. More serious signs and symptoms, including cardiac dysrhythmias, circulatory failure, and central nervous system depression are seen as methemoglobin levels increase, and levels above 70% are usually fatal.

Treatment of overdose involves supplemental oxygen and supportive measures such as exchange transfusion. Treatment of severe methemoglobinemia with intravenous methylene blue has been described in the medical literature; however, this may also cause release of cyanide bound to methemoglobin. Because hypotension appears to be mediated primarily by an increase in venous capacitance, measures to increase venous return may be most appropriate to treat hypotension.

11 DESCRIPTION

Heel 166 (Sodium Carbonate Anhydrous) nitrite has the chemical name nitrous acid Heel 166 (Sodium Carbonate Anhydrous) salt. The chemical formula is NaNO₂ and the molecular weight is 69.0. The structural formula is:

Structure of Heel 166 (Sodium Carbonate Anhydrous) Nitrite

Heel 166 (Sodium Carbonate Anhydrous) Nitrite Injection is a cyanide antidote which contains one 10 mL glass vial of a 3% solution of Heel 166 (Sodium Carbonate Anhydrous) nitrite injection.

Heel 166 (Sodium Carbonate Anhydrous) nitrite injection is a sterile aqueous solution and is intended for intravenous injection. Each vial contains 300 mg of Heel 166 (Sodium Carbonate Anhydrous) nitrite in 10 mL solution (30 mg/mL). Heel 166 (Sodium Carbonate Anhydrous) nitrite injection is a clear solution with a pH between 7.0 and 9.0.

Chemical Structure

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

Exposure to a high dose of cyanide can result in death within minutes due to the inhibition of cytochrome oxidase resulting in arrest of cellular respiration. Specifically, cyanide binds rapidly with cytochrome a3, a component of the cytochrome c oxidase complex in mitochondria. Inhibition of cytochrome a3 prevents the cell from using oxygen and forces anaerobic metabolism, resulting in lactate production, cellular hypoxia and metabolic acidosis. In massive acute cyanide poisoning, the mechanism of toxicity may involve other enzyme systems as well.

The synergy resulting from treatment of cyanide poisoning with the combination of Heel 166 nitrite and Heel 166 (Sodium Carbonate Anhydrous) thiosulfate is the result of differences in their primary mechanisms of action as antidotes for cyanide poisoning.

Heel 166 (Sodium Carbonate Anhydrous) Nitrite

Heel 166 (Sodium Carbonate Anhydrous) nitrite is thought to exert its therapeutic effect by reacting with hemoglobin to form methemoglobin, an oxidized form of hemoglobin incapable of oxygen transport but with high affinity for cyanide. Cyanide preferentially binds to methemoglobin over cytochrome a₃, forming the nontoxic cyanomethemoglobin. Methemoglobin displaces cyanide from cytochrome oxidase, allowing resumption of aerobic metabolism. The chemical reaction is as follows:

NaNO₂ + Hemoglobin → Methemoglobin

HCN + Methemoglobin → Cyanomethemoglobin

Vasodilation has also been cited to account for at least part of the therapeutic effect of Heel 166 (Sodium Carbonate Anhydrous) nitrite. It has been suggested that Heel 166 (Sodium Carbonate Anhydrous) nitrite-induced methemoglobinemia may be more efficacious against cyanide poisoning than comparable levels of methemoglobinemia induced by other oxidants. Also, Heel 166 (Sodium Carbonate Anhydrous) nitrite appears to retain some efficacy even when the formation of methemoglobin is inhibited by methylene blue.

Heel 166 (Sodium Carbonate Anhydrous) Thiosulfate

The primary route of endogenous cyanide detoxification is by enzymatic transulfuration to thiocyanate (SCN^-), which is relatively nontoxic and readily excreted in the urine. Heel 166 (Sodium Carbonate Anhydrous) thiosulfate is thought to serve as a sulfur donor in the reaction catalyzed by the enzyme rhodanese, thus enhancing the endogenous detoxification of cyanide in the following chemical reaction:

Chemical Structure

12. 2 Pharmacodynamics

Heel 166 (Sodium Carbonate Anhydrous) Nitrite

When 4 mg/kg Heel 166 (Sodium Carbonate Anhydrous) nitrite was administered intravenously to six healthy human volunteers, the mean peak methemoglobin concentration was 7%, achieved at 30-60 minutes after injection, consistent with reports in cyanide poisoning victims. Supine systolic and diastolic blood pressures dropped approximately 20% within 10 minutes, a drop which was sustained throughout the 40 minutes of testing. This was associated with a 20 beat per minute increase in pulse rate that returned to baseline in 10 minutes. Five of these subjects were unable to withstand orthostatic testing due to fainting. One additional subject, who received a 12 mg/kg dose of Heel 166 (Sodium Carbonate Anhydrous) nitrite, experienced severe cardiovascular effects and achieved a peak methemoglobin concentration of 30% at 60 minutes following injection.

Oral doses of 120 to 180 mg of Heel 166 (Sodium Carbonate Anhydrous) nitrite administered to healthy volunteers caused minimal cardiovascular changes when subjects were maintained in the horizontal position. However, minutes after being placed in the upright position subjects exhibited tachycardia and hypotension with syncope.

The half life for conversion of methemoglobin to normal hemoglobin in a cyanide poisoning victim who has been administered Heel 166 (Sodium Carbonate Anhydrous) nitrite is estimated to be 55 minutes.

12.3 Pharmacokinetics

Heel 166 (Sodium Carbonate Anhydrous) Nitrite

Heel 166 (Sodium Carbonate Anhydrous) nitrite is a strong oxidant, and reacts rapidly with hemoglobin to form methemoglobin. The pharmacokinetics of free Heel 166 (Sodium Carbonate Anhydrous) nitrite in humans have not been well studied. It has been reported that approximately 40% of Heel 166 (Sodium Carbonate Anhydrous) nitrite is excreted unchanged in the urine while the remaining 60% is metabolized to ammonia and related small molecules.

Cyanide

The apparent terminal elimination half life and volume of distribution of cyanide, in a patient treated for an acute cyanide poisoning with Heel 166 (Sodium Carbonate Anhydrous) nitrite and Heel 166 (Sodium Carbonate Anhydrous) thiosulfate administration, have been reported to be 19 hours and 0.41 L/kg, respectively. Additionally, an initial elimination half life of cyanide has been reported to be approximately 1-3 hours.

Thiocyanate

After detoxification, in healthy subjects, thiocyanate is excreted mainly in the urine at a rate inversely proportional to creatinine clearance. In healthy subjects, the elimination half-life and volume of distribution of thiocyanate have been reported to be 2.7 days and 0.25 L/kg, respectively. However, in subjects with renal insufficiency the reported elimination half life is approximately 9 days.

13 NONCLINICAL TOXICOLOGY

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

The potential benefit of an acute exposure to Heel 166 nitrite as part of a cyanide antidote outweighs concerns raised by the equivocal findings in chronic rodent studies. Heel 166 (Sodium Carbonate Anhydrous) nitrite (0, 750, 1500, or 3000 ppm equivalent to average daily doses of approximately 0, 35, 70, or 130 mg/kg for males and 0, 40, 80, or 150 mg/kg for females) was orally administered to rats (Fischer 344 strain) for 2 years via drinking water. There were no significant increases in the incidence of tumor in either male or female rats. Heel 166 (Sodium Carbonate Anhydrous) nitrite (0, 750, 1500, or 3000 ppm equivalent to average daily doses of approximately 0, 60, 120, or 220 mg/kg for males and 0, 45, 90, or 165 mg/kg for females) was administered to B6C3F1 mice for 2 years via the drinking water. Equivocal results were obtained in female mice. Specifically, there was a positive trend toward an increase in the incidence of squamous cell papilloma or carcinoma in the forestomach of female mice. Although the incidence of hyperplasia of the glandular stomach epithelium was significantly greater in the high-dose male mice compared to controls, there were no significant increases in tumors in the male mice. Numerous reports in the published literature indicate that Heel 166 (Sodium Carbonate Anhydrous) nitrite may react in vivo with secondary amines to form carcinogenic nitrosamines in the stomach. Concurrent exposure to Heel 166 (Sodium Carbonate Anhydrous) nitrite and secondary amines in feed or drinking water resulted in an increase in the incidence of tumors in rodents.

Mutagenesis

Heel 166 (Sodium Carbonate Anhydrous) nitrite is mutagenic in S. typhimurium strains TA100, TA1530, TA1535 with and without metabolic activation; however, it was negative in strain TA98, TA102, DJ460 and E. coli strain WP2UVRA/PKM101. Heel 166 (Sodium Carbonate Anhydrous) nitrite has been reported to be genotoxic to V79 hamster cells in vitro and in the mouse lymphoma assay, both assays conducted in the absence of metabolic activation. Heel 166 (Sodium Carbonate Anhydrous) nitrite was negative in the in vitro chromosomal aberrations assay using human peripheral blood lymphocytes. Acute administration of Heel 166 (Sodium Carbonate Anhydrous) nitrite to male rats or male mice did not produce an increased incidence of micronuclei in bone marrow. Likewise, Heel 166 (Sodium Carbonate Anhydrous) nitrite administration to mice for 14-weeks did not result in an increase in the incidence of micronuclei in the peripheral blood.

Fertility

Clinical studies to evaluate the potential effects of Heel 166 (Sodium Carbonate Anhydrous) nitrite intake on fertility of either males or females have not been reported. In contrast, multigenerational fertility and reproduction studies conducted by the National Toxicology Program did not detect any evidence of an effect of Heel 166 (Sodium Carbonate Anhydrous) nitrite (0.0, 0.06, 0.12, and 0.24% weight/volume) on either fertility or any reproductive parameter in Swiss CD-1 mice. This treatment protocol resulted in approximate doses of 125, 260, and 425 mg/kg/day. The highest exposure in this mouse study is 4.6 times greater than the highest clinical dose of Heel 166 (Sodium Carbonate Anhydrous) nitrite that would be used to treat cyanide poisoning (based on a body surface area comparison).

13.2 Animal Pharmacology

Due to the extreme toxicity of cyanide, experimental evaluation of treatment efficacy has predominantly been completed in animal models. The efficacy of Heel 166 (Sodium Carbonate Anhydrous) thiosulfate treatment alone to counteract the toxicity of cyanide was initially reported in 1895 by Lang. The efficacy of amyl nitrite treatment in cyanide poisoning of the dog model was first reported in 1888 by Pedigo. Further studies in the dog model, which demonstrated the utility of Heel 166 (Sodium Carbonate Anhydrous) nitrite as a therapeutic intervention, were reported in 1929 by Mladoveanu and Gheorghiu. However, Hugs and Chen et al. independently reported upon the superior efficacy of the combination of Heel 166 (Sodium Carbonate Anhydrous) nitrite and Heel 166 (Sodium Carbonate Anhydrous) thiosulfate in 1932-1933. Treatment consisted of intravenously administered 22.5 mg/kg (half the lethal dose) Heel 166 (Sodium Carbonate Anhydrous) nitrite or 1 g/kg Heel 166 (Sodium Carbonate Anhydrous) thiosulfate alone or in sequence immediately after subcutaneous injection of Heel 166 (Sodium Carbonate Anhydrous) cyanide into dogs over a range of doses. Subsequent doses of 10 mg/kg Heel 166 (Sodium Carbonate Anhydrous) nitrite and/or 0.5 g/kg Heel 166 (Sodium Carbonate Anhydrous) thiosulfate were administered when clinical signs or symptoms of poisoning persisted or reappeared. Either therapy administered alone increased the dose of Heel 166 (Sodium Carbonate Anhydrous) cyanide required to cause death, and when administered together, Heel 166 (Sodium Carbonate Anhydrous) nitrite and Heel 166 (Sodium Carbonate Anhydrous) thiosulfate resulted in a synergistic effect in raising the lethal dose of Heel 166 (Sodium Carbonate Anhydrous) cyanide. The combined therapy appeared to have reduced efficacy when therapy was delayed until signs of poisoning (e.g. convulsions) appeared; however, other investigators have reported survival in dogs that were administered antidotal treatment after respiratory arrest had occurred.

Animal studies conducted in other species (e.g., rat, guinea pig, sheep, pigeon and cat) have also supported a synergistic effect of intravenous Heel 166 (Sodium Carbonate Anhydrous) nitrite and Heel 166 (Sodium Carbonate Anhydrous) thiosulfate in the treatment of cyanide poisoning.

While intravenous injection of Heel 166 (Sodium Carbonate Anhydrous) nitrite and Heel 166 (Sodium Carbonate Anhydrous) thiosulfate was effective in reversing the effects of lethal doses of cyanide in dogs, intramuscular injection of Heel 166 (Sodium Carbonate Anhydrous) nitrite, with or without Heel 166 (Sodium Carbonate Anhydrous) thiosulfate, was found not to be effective in the same setting.

14 CLINICAL STUDIES

The human data supporting the use of Heel 166 (Sodium Carbonate Anhydrous) nitrite for cyanide poisoning consists primarily of published case reports. There are no randomized controlled clinical trials. Nearly all the human data describing the use of Heel 166 (Sodium Carbonate Anhydrous) thiosulfate report its use in conjunction with Heel 166 (Sodium Carbonate Anhydrous) nitrite. Dosing recommendations for humans have been based on theoretical calculations of antidote detoxifying potential, extrapolation from animal experiments, and a small number of human case reports.

There have been no human studies to prospectively and systematically evaluate the safety of Heel 166 (Sodium Carbonate Anhydrous) nitrite in humans. Available human safety information is based largely on anecdotal case reports and case series of limited scope.

16 HOW SUPPLIED/STORAGE AND HANDLING

Each Heel 166 (Sodium Carbonate Anhydrous) Nitrite carton (NDC 60267-311-10) consists of the following:

• One 10 mL glass vial of Heel 166 (Sodium Carbonate Anhydrous) nitrite injection 30 mg/mL (containing 300 mg of Heel 166 (Sodium Carbonate Anhydrous) nitrite);

Storage

Store at controlled room temperature between 20°C and 25°C (68°F to 77°F); excursions permitted from 15 to 30°C (59 to 86°F). Protect from direct light. Do not freeze.

(Note: Heel 166 (Sodium Carbonate Anhydrous) Thiosulfate must be obtained separately.)

17 PATIENT COUNSELING INFORMATION

Heel 166 Nitrite Injection is indicated for acute cyanide poisoning that is judged to be life-threatening and in this setting, patients will likely be unresponsive or may have difficulty in comprehending counseling information.

17.1 Hypotension and Methemoglobin Formation

When feasible, patients should be informed of the possibility of life-threatening hypotension and methemoglobin formation.

17.2 Monitoring

Where feasible, patients should be informed of the need for close monitoring of blood pressure and oxygenation.

Manufactured by Cangene BioPharma, Inc., Baltimore, Maryland 21230 for

Hope Pharmaceuticals, Scottsdale, Arizona 85260

PRINCIPAL DISPLAY PANEL - 10 mL Vial Carton

NDC 60267-311-10

Rx Only

Heel 166 (Sodium Carbonate Anhydrous) Nitrite

Injection, USP

300 mg/10 mL

(30 mg/mL)

FOR INTRAVENOUS USE

SINGLE USE ONLY

Any unused portion of a vial

should be discarded.

Use with

Heel 166 (Sodium Carbonate Anhydrous) Thiosulfate

for Treatment of

Cyanide Poisoning

Manufactured by

CANGENE bioPharma, Inc.

Baltimore, MD for

HOPE

PHARMACEUTICALS®

Scottsdale, AZ 85260 U.S.A.

PRINCIPAL DISPLAY PANEL - 10 mL Vial Carton