Composition that comprises at least one oxime and its use in therapeutics

This invention relates to a composition that comprises at least one oxime and its use for the treatment of respiratory poisoning caused by organophosphorus compounds.

The organophosphates (OP) constitute a big family of chemical compounds that have been synthesized since the 1940\'s and that have been introduced as highly effective pesticides (P. Taylor, Anticholinesterase Agents in: Goodman, A.; Goodman, L. S.; Rall, T. W.; Murad, F. (eds.), The Pharmacological Basis of Therapeutics, 1985, 7^th Ed. MacMillan, New York, pp. 100-119). These substances pose a high risk for public health due to the high frequency of poisonings: according to data from the World Health Organization, there are more then 3 million cases of severe poisoning by organophosphorus compounds and more than 220,000 deaths annually (WHO, Public Health Impact of Pesticides Used in Agriculture, Geneva 1990; WHO, Officina San itaria Panamericana, Plaguicidas y Salud en las Americas, Serie Ambiental 12, Washington D.C., 1993; Segura et al., Arch. Pharmacol., 1999, 360: 699-710). The organophosphates that are widely used in agriculture and veterinary medicine as insecticides and antihelminthic compounds are inhibitors of cholinesterases (acetylcholinesterase, butyrylcholinesterase, carboxyesterase). The inhibition of acetyleholinesterase in the central and peripheral nervous tissues causes the accumulation of the cholinergic neuromediator, acetylcholine, at the level of cholinergic synapses, which induces hyperactivation of muscarinic, nicotinic and central receptors followed by their desensitization. The hyperactivation of the postganglionic nicotinic receptors stimulates the neurotransmission in the sympathetic and parasympathetic fibers. The stimulation of the postganglionic muscarinic receptors of the parasympathetic fibers induces the appearance of the muscarinic syndrome (hypersalivation, watering of the eye, sweating, rhinorrhea, bronchorrhea, dyspnea, bronchial spasm, myosis, accommodation paralysis, abdominal pains, vomiting, diarrhea, involuntary urination, hypotension, bradycardia, and auriculoventricular conduction problems). The hyperactivation of the postsynaptic nicotinic receptors at the neuromuscular junction induces the nicotinic syndrome (fasciculations, asthenia, and muscular paralysis). Sympathetic hyperstimulation is responsible for sinus tachycardia, myocardial hyperexcitability, hypertensive episodes and hypokalemia. At the level of the central nervous system, the accumulation of acetylcholine can cause various effects such as anxiety, confusion, speech problems, convulsions, ataxia, and coma (Namba et al. Am. J Med., 1971, 50: 475-492; T. Namba, Med. Times, 1972, 100: 100-126; W. J. Hayes, Jr., Pesticides Studied in Man, 1982, Williams and Wilkins, Baltimore, Md., pp. 284-435; D. J. Humphreys, Veterinary Toxicology, 1988, 3^rd Ed. Bailliere Tindall, Philadelphia; Landier et al. Urgences [Emergencies], 1995, XIV: 213-215). Certain organophosphorus compounds also bring about the phosphorylation of another type of esterase: the neuropathy target esterase (ITE) (Aldrige and Barnes, Biochem Pharmacol, 1966, 15: 549-554), whose inhibition is contemporaneous with a central and peripheral ascending distal axonopathy that takes place two to five weeks after the poisoning (M. B. Abou-Donia, Science, 1979, 205: 713-715).

It has been documented that the major cause of death, in the event of severe and acute poisoning by an organophosphorus compound, is due to a respiratory depression of central origin or to a peripheral respiratory insufficiency, resulting from the paralysis of the diaphragm muscle; death may also be due to cardiac arrest (Durham and Hayes, Arch. Environ Health, 1962, 5: 27-53; Humphreys, 1988, supra; Lerman and Gutman, Med. Hypotheses, 1988, 26: 267-269; M. Yamashita, Vet. Human Toxicol., 1997, 39: 84; Poinsindex, CD-ROM Edition, 2000, Vol. 103, Micromedex). The respiratory problems caused by poisoning with the organophosphorus compounds are highly complex: they are the result of the combination of muscarinic syndromes (bronchial spasms, bronchorrhea), nicotinie syndromes (paresis and paralysis of respiratory muscles) (Lund and Monteagudo, S. Afr. Med., 1986, 69: 6; Dive et al., Human Exp Toxicol., 1994, 13: 271-274; Betrosian et al., J. Toxicol. Clin. Toxicol., 1995, 33: 257-260; Thompson and Stocks, Arch. Otolaryngol.—Head Neck Surg., 1997, 123; 93-96) and central syndromes (coma with obstructive apnea), whereby the latter is not specific to poisoning but common to all the coma states.

Studies of electrophysiology and histology in vitro have shown that the inhibitors of the cholinesterases depress the diaphragmatic contractility in rats (J. G. Clément, Eur. J. Pharmacol., 1979, 53: 135-141; French et al., Eur. J. Pharmacol., 1983, 91: 399-409; A. P. Smith, J. Pharm. Pharmacol., 1993, 45: 176-181), and certain recent studies even show a partial necrosis of muscular fibers (J. De Bleecker, J. Toxicol.—Clin. Toxicol., 1995, 33: 683-686; Cavalière et al, Rev Saude Publica, 1998, 30: 267-272). In vivo studies in men (De Bleecker 1995, supra) and in rats (De Bleecker et al., Neurotoxicology, 1994, 15: 331-340; De Bleecker 1995, supra; Dongren et al., Toxicol Letters, 1999, 107: 249-254) have shown that the late-onset syndromes during poisoning with weakness and paralysis of the upper and lower members are combined with an alteration of the electromyographic parameters of peripheral, muscular fibers. However, there do not exist, to our knowledge, works that have studied the respiratory effects in vivo of an organophosphate poisoning, whereas this device seems to be the essential target of these poisons.

The antidote that is conventionally used against poisoning with organophosphates consists of atroprine. However, the administered doses should be very high and should be repeated for at least 24 hours so that the patient has a reduction of symptoms without the definitive return to a normal state being ensured. The administration of this antidote is systematically combined with measures for decontamination and symptomatic treatments (tracheal incubation, bronchial inhalations and treatment of convulsions, in particular by diazepam).

There is therefore a real need for means for more effective treatment of respiratory poisoning caused by organophosphates that are present in particular in pesticides, and in particular means for allowing patients to recover very quickly and sustainably the respiratory capacity they had before being poisoned.

The filing company, after much research, has had the great advantage of finding that it was possible to improve the recovery of a patient who has been poisoned by organophosphates by blocking the specific organic cation transporters at the renal level of the poisoned patient and by administering to the patient an effective amount of an oxime or a mixture of oximes with preferential renal elimination.

In this invention, the term “patients” covers human beings and animals. The term “oxime” is used to refer to an oxime or a mixture of oximes with preferential renal elimination. The oxime can be used as such or in the form of its salts and pharmaceutically acceptable hydrates. By way of example of oxime, it is possible to cite in particular pralidoxime, obidoxime, Hi-6 and mixtures thereof. By way of example of pharmaceutically acceptable salts, it is possible to cite methyl sulfate, iodide, chloride, and methanesulfonate. The term “blocking of the OCT [organic cationic transporter]” is used in this description to designate the blocking of specific organic cation transporters at the renal level.

Under pathological conditions, the blocking of the OCT may be due to renal insufficiency of the patient, in which case only oxime is administered to the patient.

The blocking of the OCT can also be caused by the administration of a chemical substance. The blocking of the OCT is then temporary.

The patient who has undergone poisoning caused by organophosphates whose OCT have been blocked and to whom at least one oxime has been administered quickly and sustainably recovers all his respiratory functions.

Thus, the invention relates to the use of at least one oxime in an effective amount for the treatment of the poisoning by organophosphorus compounds of patients whose OCT have been blocked.

The invention relates to the use of at least one oxime for the preparation of a medication that is intended for the treatment of the poisoning of patients whose OCT have been blocked.

The OCT1, 2 and 3 can all be blocked or else at least OCT 1 and 2 are blocked.

The patients whose OCT have been blocked can be patients that have renal insufficiency (pathological conditions) or else patients in whom the blocking of the OCT has been brought about in particular by administration of a chemical agent.

The poisoning suffered by the patients that the invention has as its object to treat is a poisoning caused by organophosphorus compounds (which are referred to in the text either as organophosphorus compounds or organophosphates). These organophosphorus compounds are active substances that are used as pesticides in agriculture. By way of examples of such organophosphorus compounds, it is possible to cite in particular paraoxon, dichlorvos, chlorpyrifos, fenthion, and dimethoate.

According to a particular embodiment of the invention, the administration of oxime and the agent that blocks the OCT can be done sequentially, simultaneously or successively. According to an advantageous embodiment, the administration of the agent blocking the OCT is done before the administration of oxime. The administration of the blocking agent can be done in approximately 60 minutes, preferably approximately 30 minutes, and, more preferably still, approximately 15 minutes before the oxime is administered.

The administration can be done orally or parenterally. The oxime can be administered, for example, by injection, and the agent that blocks the OCT can be administered orally.

The amount of oxime will be determined by the doctor on the basis in particular of weight, the condition of the patient to be treated, the method of administration and/or the extent of the poisoning. In general, a loading dose on the order of 1 to 10, preferably 5 mg/kg of body weight, is administered, then so-called maintenance doses on the order of 20 to 100, preferably 25 to 50 mg/kg of body weight and per day, are administered regularly, for example every hour for 12 to 48 hours.

The amount of agent blocking the OCT will be determined by the doctor on the basis in particular of weight, condition, age, and sex of the patient to be treated as well as the method of administration and the duration of the temporary condition desired.

Another object of the invention is a medication that comprises at least one oxime and at least one agent that blocks the OCT as active ingredients.

This invention also relates to a pharmaceutical composition that comprises at least one oxime and at least one agent that blocks the OCT as active ingredients as well as at least one pharmaceutically acceptable vehicle.

The pharmaceutical composition according to the invention can be administered sequentially, simultaneously or successively and comprises at least one oxime, optionally with at least a first vehicle, and at least one agent that blocks the OCT, optionally with at least a second vehicle, whereby the first vehicle can be identical to the second vehicle.