Individuals without methaemoglobinaemia
The administration of large intravenous doses (> 7 mg/kg) of Methylthioniniumchlorid Proveblue to individuals without methaemoglobinaemia induces nausea and vomiting, chest tightness, chest pain, tachycardia, apprehension, severe sweating, tremor, mydriasis, blue-green staining of the urine, blue staining of the skin and mucous membranes, abdominal pain, dizziness, paraesthesia, headache, confusion, hypertension, mild methaemoglobinaemia (up to 7%) and electrocardiogram changes (T wave flattening or inversion). These features resolve generally within 2-12 hours of the injection.
Individuals with methaemoglobinaemia
Cumulative doses of Methylthioninium chloride may lead to dyspnoea and tachypnoea, presumably related to reduced oxygen availability caused by methaemoglobinaemia, chest pain, tremor, cyanosis and haemolytic anaemia.
Haemolytic anaemia has also been reported in case of severe overdose (20-30 mg/kg) in infants and adults with methaemoglobinaemia caused by aniline or chlorates. Haemodialysis may be used in patients with severe haemolysis.
Paediatric population
Hyperbilirubinaemia has been observed in infants after administration of 20 mg/kg methylthioninium chloride.
Death occurred in 2 infants after administration of 20 mg/kg methylthioninium chloride. Both infants had complex medical circumstances and methylthioninium chloride was only partially responsible.
The patient should be maintained under observation, the methaemoglobin level should be monitored and appropriate supportive measures taken as necessary.
- Hypersensitivity to the active substance, or to any other thiazine dyes
- Patients with Glucose-6-phosphate dehydrogenase deficiency (G6PD) due to the risk of haemolytic anaemia
- Patients with nitrite-induced methaemoglobinaemia during treatment of cyanide poisoning
- Patients with methaemoglobinaemia due to chlorate poisoning
- Deficiency in NADPH (nicotinamide adenine dinucleotide phosphate) reductase.
It must especially not be mixed with sodium chloride 9 mg/ml (0.9%) solution for injection because it has been demonstrated that chloride reduces the solubility of methylthioninium chloride.
Summary of the safety profile
The most commonly reported adverse reactions observed during clinical trials are dizziness, paraesthesia, dysgeusia, nausea, skin discoloration, chromaturia, sweating, injection site pain and pain in extremity.
Intravenous injection of methylthioninium chloride has occasionally caused hypotension and cardiac arrhythmias, and such disorders might prove fatal on rare occasions.
Tabulated list of adverse reactions
The adverse reactions listed in the table below occur in adults, children and adolescents (aged 0 to 17 years old) after intravenous administration. The frequencies are not known (cannot be estimated from the available data). When indicated, the frequency is based on a very small sample size.
| System organ class | Adverse reactions | Frequency |
| Blood and lymphatic system disorders | Methaemoglobinaemia, | Not known |
| Hyperbilirubinaemia1 | Not known | |
| Haemolytic anaemia | Not known | |
| Immune system disorders | Anaphylactic reactions | Not known |
| Psychiatric disorders | Confusional state | Not known |
| Agitation | Not known | |
| Nervous system disorders | Dizziness | Very common |
| Headache | Common | |
| Anxiety | Common | |
| Tremor | Not known | |
| Fever | Not known | |
| Aphasia | Not known | |
| Paraesthesia | Very common | |
| Dysgeusia | Very common | |
| Serotonin Syndrome with concomitant use of serotonergic drugs. | Not known | |
| Eye disorders | Mydriasis | Not known |
| Cardiac disorders | Cardiac arrhythmia | Not known |
| Tachycardia | Not known | |
| Vascular disorders | Hypertension | Not known |
| Hypotension | Not known | |
| Respiratory, thoracic and mediastinal disorders | Dyspnoea | Not known |
| Tachypnoea | Not known | |
| Hypoxia | Not known | |
| Gastrointestinal disorders | Nausea | Very common |
| Vomiting | Common | |
| Abdominal pain | Common | |
| Faeces discoloration (blue-green) | Not known | |
| Skin and subcutaneous tissue disorders | Skin discoloration (blue) | Very common |
| Sweating | Very common | |
| Urticaria | Not known | |
| Phototoxicity / Photosensitivity | Not known | |
| Renal and urinary disorders | Chromaturia (blue-green) | Very common |
| General disorders and administration site conditions | Chest pain | Common |
| Local tissue necrosis at the injection site | Not known | |
| Injection site pain | Common | |
| Investigations | Haemoglobin decreased | Not known |
| Musculoskeletal and connective tissue disorder | Pain in extremity | Very common |
1 Reported in infants only
Paediatric population
Adverse reactions are the same as in adults (except hyperbilirubinaemia, reported in infants only).
Reporting of suspected adverse reactions
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via:
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Repeated dose toxicity
One-month repeated dose toxicity in dogs showed no macroscopic toxic effects.
Adverse reactions, seen at exposure levels similar to clinical exposure levels and with possible relevance to clinical use were moderate regenerative anaemia associated with increased mean platelet count and fibrinogen levels, a minimal increase in mean total bilirubin blood values and an increased incidence of moderate urine bilirubin levels.
Genotoxicity
Methylthioninium chloride was mutagenic in gene mutation assays in bacteria and mouse lymphoma cells but not in vivo mouse micronucleus assay when administered intravenously at 62 mg/kg.
Carcinogenicity
Some evidence of carcinogenic activity of methylthioniniul chloride has been shown in male mice and male rats. An equivocal evidence of carcinogenic activity was observed in female mice. No evidence of carcinogenic activity was observed in female rats.
Reproductive Toxicology
In vitro, methylthioninium chloride has been shown to reduce motility of human sperm in a dose dependant manner. It has also been shown to inhibit the growth of cultured two-cell mouse embryos and the production of progesterone in cultured human luteal cells.
In rats and rabbits, teratogenic effects have been reported, with foetal and maternal toxicity. In rats, increased resorption rates have been observed.
Acute symptomatic treatment of medicinal and chemical products-induced methaemoglobinaemia.
Methylthioniniumchlorid Proveblue is indicated in adults, children and adolescents (aged 0 to 17 years old).
Pharmacotherapeutic group: All other therapeutic products, antidotes, ATC code: V03AB17
In vivo, in low concentration, methylthioninium chloride speeds up the conversion of methaemoglobin to haemoglobin.
Methylthioniniumchlorid Proveblue has been observed to stain tissues selectively. Its use in parathyroid surgery (not indicated) has induced adverse CNS effects when administered concomitantly with serotonergic medicinal products.
Paediatric population
The efficacy of methylthioninium chloride for the treatment of methaemoglobinaemia in peadiatric population was demonstrated in two retrospective studies and one open randomised clinical trial. Case reports of efficacy are also available in literature.
After intravenous administration Methylthioniniumchlorid Proveblue is rapidly taken up by the tissues. It is also well absorbed by the oral route. The majority of the dose is excreted in the urine, usually in the form of leucomethylthioninium chloride.
The estimated terminal half-life of methylthioninium chloride after intravenous administration is 26.7h.
Methylthioniniumchlorid Proveblue is not an in vitro inducer of CYP2B6 and CYP3A4.
Methylthioniniumchlorid Proveblue is an in vitro inhibitor of P-gp.
Methylthioniniumchlorid Proveblue is not an in vitro substrate for BCRP or OCT2 and is not an in vitro inhibitor of BCRP, OAT1 or OAT3.
General
Methylthioniniumchlorid Proveblue must be injected very slowly over a period of 5 minutes to prevent high local concentrations of the compound from producing additional methaemoglobin.
It imparts a blue-green colour to urine, faeces and a blue colour to skin which may hinder a diagnosis of cyanosis.
In patients with aniline-induced methaemoglobinaemia, repeated doses of methylthioninium chloride may be required. Caution should be exercised in the course of treatment with methylthioninium chloride as this may exacerbate Heinz body formation and haemolytic anaemia. Lower doses should therefore be considered and total cumulative dose should not exceed 4 mg/kg.
Methylthioniniumchlorid Proveblue can exacerbate dapsone-induced haemolytic anemia because of the formation of the dapsone reactive metabolite hydroxylamine which oxidises haemoglobin. It is recommended not to exceed a cumulative dose for the course of treatment of 4 mg/kg in patients with dapsone-induced methaemoglobinaemia.
In cases of suspected methaemoglobinaemia, it is advisable to check the oxygen saturation by co-oximetry when available since pulse oximetry may provide a false estimation of oxygen saturation during administration of methylthioninium chloride.
Anaesthesiologists should be vigilant for methaemoglobinaemia in patients receiving dapsone therapy and for BIS (Bispectral Index) interference with Methylthioniniumchlorid Proveblue administration.
Electrocardiogram (ECG) and blood pressure should be monitored during and after treatment with Methylthioniniumchlorid Proveblue as hypotension and cardiac arrhythmia are potential adverse reactions.
Failure to respond to methylthioninium chloride suggests cytochrome b5 reductase deficiency, glucose-6- phosphate dehydrogenase deficiency or sulfhaemoglobinemia. Alternative treatment options should be considered.
Methylthioninium chloride may cause serious or fatal serotonergic syndrome when used in combination with serotonergic drugs. Avoid concomitant use of methylthioninium chloride with selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), and monoamine oxidase inhibitors.
Patients treated with methylthioninium chloride in combination with serotonergic drugs should be monitored for the emergence of serotonin syndrome. If symptoms of serotonin syndrome occur, discontinue use of methylthioninium chloride, and initiate supportive treatment.
Patients with hyperglycaemia or diabetes mellitus
If diluted in glucose 50 mg/ml (5%) solution for injection, methylthioninium chloride must be used with caution in patients with hyperglycaemia or diabetes mellitus, as these conditions may be exacerbated by the glucose solution.
Paediatric population
Extreme caution should be exercised when administering to newborns and infants below the age of 3 months due to lower concentrations of NADPH-methaemoglobin reductase necessary for reducing methaemoglobin to haemoglobin, making these infants more susceptible to methaemoglobinaemia produced by high doses of methylthioninium chloride.
Photosensitivity
Methylthioninium chloride may cause a cutaneous photosensitivity reaction when exposed to strong light sources, such as phototherapy, those found in operating theatres or locally from illuminating devices such as pulse oximeters.
Advise patients to take protective measures against exposure to light, because photosensitivity may occur after administration of methylthioninium chloride.
Methylthioninium chloride has moderate influence on the ability to drive and use machines. Indeed, driving can be affected due to confusional state, dizziness and possibly eye disturbances.
However, the risk is limited as the medicinal product is intended for acute administration only in emergency situations at hospital.
Methylthioniniumchlorid Proveblue is for administration by a healthcare professional.
Posology
Adults
The usual dose is 1 to 2 mg per kg body weight, i.e. 0.2-0.4 ml per kg body weight, given over a period of 5 minutes.
A repeat dose (1 to 2 mg/kg body weight, i.e. 0.2-0.4 ml/kg body weight) may be given one hour after the first dose in cases of persistent or recurrent symptoms or if methaemoglobin levels remain significantly higher than the normal clinical range.
Treatment does not usually exceed one day.
The maximum recommended cumulative dose for the course of treatment is 7 mg/kg and should not be exceeded, since Methylthioninium chloride administered above the maximum dose may cause methaemoglobinaemia in susceptible patients.
In the case of aniline- or dapsone-induced methaemaglobinaemia, the maximum recommended cumulative dose for the course of treatment is 4 mg/kg.
Too limited data are available to support a continuous infusion dose recommendation.
Special populations
Elderly
No dose adjustment is necessary.
Renal impairment
Methylthioninium chloride should be used with caution in patients with moderate to severe renal disease since there is limited data available and methylthioninium chloride is predominantly renally eliminated. Lower doses (<1 mg/kg) may be needed.
Hepatic impairment
There is no experience in patients with severe hepatic impairment.
Paediatric population
Infants above 3 months, children and adolescents:
Same posology as for adults.
Infants 3 months old or younger and newborn infants:
The recommended dose is 0.3-0.5 mg/kg body weight, i.e. 0.06 to 0.1 ml/kg body weight, given over a period of 5 minutes.
A repeat dose (0.3 to 0.5 mg/kg body weight, i.e. 0.06-0.1 ml/kg body weight) may be given one hour after the first dose in cases of persistent or recurrent symptoms or if methaemoglobin levels remain significantly higher than the normal clinical range (see section 4.4 for important safety information).
Treatment does not usually exceed one day.
Method of administration
For intravenous use.
Methylthioniniumchlorid Proveblue is hypotonic and may be diluted in 50 ml glucose 50 mg/ml (5%) solution for injection to avoid local pain, in particular in paediatric population.
It must be injected very slowly over a period of 5 minutes.
It must not be administered by subcutaneous or intrathecal injection.
For single use only
Methylthioniniumchlorid Proveblue may be diluted in 50 ml glucose 50 mg/ml (5%) solution for injection to avoid local pain, in particular in paediatric population.
Before any administration, it is recommended to inspect the parenteral solutions to verify that they are free of particles. Do not use Methylthioniniumchlorid Proveblue if the solution is discoloured, cloudy, turbid, or a precipitate or particles are present.
Any unused product or waste material should be disposed of in accordance with local requirements.
