Symptoms
Symptoms of over dosage include malaise, nausea, vomiting, lacrimation and salivation, burning sensation of lips, mouth, throat and eyes with headache. A sense of constriction of the throat and chest. Increased blood pressure maximal after 15-20 minutes. Transient effects lasting about four hours.
Management
Treatment consists of the subcutaneous administration of diphenhydramine 50 mg or ephedrine 30 mg or ephedrine in a dosage of 30-60 mg orally if time permits.
Poisoning by iron, cadmium, or selenium.
Impaired hepatic function unless due to arsenic poisoning.
Not applicable.
Side effects are relatively frequent, but at the therapeutic dosage employed, are seldom severe enough to warrant cessation of treatment and are almost invariably reversible. There is some evidence to indicate that 30-60 mg of ephedrine sulphate by mouth, given half an hour before each injection of Dimercaprol Amdipharm, will reduce these reactions. Also, a minimum interval of four hours between doses appears to reduce side effects.
Dimercaprol Amdipharm may cause the following side effects, particularly at the higher dosage levels:
Blood and lymphatic system disorders
Haemolysis, transient reductions in leukocyte count have also been reported.
Psychiatric disorders
Anxiety, restlessness
Nervous system disorders
Headache, tingling of the hands and other extremities, tremor. High doses have produced hypertensive encephalopathy with convulsions and coma.
Eye disorders
Burning sensation of the eyes, lacrimation, conjunctivitis, blepharospasm
Cardiac disorders
Elevation of blood pressure accompanied by tachycardia
Respiratory, thoracic and mediastinal disorders
Rhinorrhoea, a feeling of constriction in the chest and throat
Gastrointestinal disorders
Nausea and possibly vomiting, salivation, abdominal pain, burning sensation of the lips, mouth and throat
Hepatobiliary disorders
Hepatotoxicity/liver injury
Skin and subcutaneous tissue disorders
Sweating of the forehead and hands
Musculoskeletal and connective tissue disorders
Muscle pain and spasm, pain in jaw
Renal and urinary disorders
Renal impairment
Reproductive system and breast disorders
Burning sensation in the penis
General disorders and administration site conditions
Local pain may occur at the site of injection and gluteal abscess has occasionally been encountered. Pyrexia.
Investigations
Activated partial thromboplastin time prolonged, blood zinc decreased
Paediatric population
A side effect apparently peculiar to children is a fever which develops after the second or third injection, and persists until treatment with Dimercaprol Amdipharm is terminated.
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 the Yellow Card Scheme (website: www.mhra.gov.uk/yellowcard).
None stated.
Dimercaprol Amdipharm Injection is indicated in adults and children for the treatment of acute poisoning by certain heavy metals, arsenic, mercury, gold, bismuth, antimony and possibly thallium. Although Dimercaprol Amdipharm has not been successful in the treatment of lead poisoning when used alone, there is evidence that used in conjunction with sodium calcium edetate, it can be used successfully in the treatment of lead poisoning, particularly in children.
Pharmacotherapeutic group: Antidote
ATC code: V03AB
Dimercaprol Amdipharm is a chelating agent used in the treatment of acute poisoning by heavy metals.
Mechanism of action
The sulphydryl groups of Dimercaprol Amdipharm compete with endogenous sulphydryl groups on proteins such as enzymes to combine with these metals; chelation by Dimercaprol Amdipharm therefore prevents or reverses any inhibition of the sulphydryl enzymes by the metal and the Dimercaprol Amdipharm-metal complex formed is readily excreted by the kidney.
Absorption
After intramuscular injection, maximum plasma concentrations of Dimercaprol Amdipharm may be attained within one hour.
Distribution
Dimercaprol Amdipharm is widely distributed to all body tissues, with the highest concentrations found in the kidneys and liver.
Biotransformation
Dimercaprol Amdipharm is rapidly metabolised and the metabolites and Dimercaprol Amdipharm-metal chelates are excreted in the urine and bile.
Elimination
Elimination is essentially complete within four hours of a single dose.
Dimercaprol Amdipharm Injection should be used with care in patients with hypertension or impaired renal function. It should be discontinued or continued with extreme caution if acute renal insufficiency develops during therapy. Dimercaprol Amdipharm Injection may not be effective in cases of concomitant renal failure, e.g. in arsine poisoning and some cases of arsenic poisoning. Any abnormal reaction (e.g. pyrexia) occurring after the initial injection of Dimercaprol Amdipharm should be assessed before continuing treatment. The use of Dimercaprol Amdipharm Injection does not eliminate the need for the general treatment of poisoning due to the particular heavy metal.
A reaction apparently peculiar to children is fever which may persist during therapy. It occurs in approximately 30% of children.
A transient reduction of the percentage of polymorphonuclear leukocytes may also be observed.
Dimercaprol Amdipharm has been reported to induce hemolysis (which may be severe) in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency. Therefore, high-risk individuals should be screened for G6PD deficiency, and susceptible patients should be monitored for hemolysis during therapy with Dimercaprol Amdipharm.
Dimecaprol Injection contains Arachis oil (peanut oil)
Dimercaprol Amdipharm Injection should not be given to patients known to be allergic to peanut. As there is a possible relationship between allergy to peanut and allergy to Soya, patients with Soya allergy should also avoid Dimercaprol Amdipharm Injection.
Dimercaprol Amdipharm Injection contains benzyl benzoate
May increase the risk of jaundice in newborn babies.
No adverse effects known.
Posology
Adults
400 - 800 mg, in divided doses, on the first day.
200 - 400 mg, in divided doses, on the second and third days.
100 - 200 mg, in divided doses, on the subsequent days.
Within the above dose range, individual dosage should be calculated on a bodyweight basis and will depend upon the severity of symptoms and the causative agent. As a general guide, single doses should not exceed 3 mg per kg bodyweight. However, in severe acute poisoning, single doses up to 5 mg per kg bodyweight may be required initially.
Paediatric population
Dimercaprol Amdipharm Injection is well tolerated by children and the dosage should be calculated on the basis of bodyweight, using the same unit dose per kg of bodyweight as for an adult under similar clinical circumstances.
Elderly
There are no specific data on the use of Dimercaprol Amdipharm in the elderly but since it is eliminated via the kidney, it should be used with caution in this age group.
Method of administration
For intramuscular injection.
Special precautions for disposal: react with weak aqueous solution (up to 15% of calcium hypochlorite). Leave for 24 hours. Neutralise and discharge to drain with copious quantities of water.
