EFFICACY OF ATROPINE NASAL AEROSOL SPRAY AGAINST ORGANOPHOSPHOROUS POISONING

Transcription

1 Indian Journal of Pharmacology 2001; 33: SHORT COMMUNICATION ATROPINE NASAL SPRAY AGAINST OP POISONING EFFICACY OF ATROPINE NASAL AEROSOL SPRAY AGAINST ORGANOPHOSPHOROUS POISONING PRAVIN KUMAR, R. VIJAYARAGHAVAN, M. SINGH* Division of Pharmacology and Toxicology, Defence Research and Development Establishment, Jhansi Road, Gwalior *Defence Research and Development Organisation, DOM, B Wing, Sena Bhavan, New Delhi Manuscript Received: Revised: Accepted: ABSTRACT Objective: The study was aimed at investigating the antagonistic efficacy of atropine nasal aerosol spray against organophosphorous poisoning on cardiovascular and respiratory variables in rats. Methods: The effect of acetylcholine (1, 2, 4 µg and 1 mg, i.v.), before and after dichlorvos (11 mg/kg, equal to 0.5 LD 50, i.p.) administration in urethane anaesthetized and tracheostomised male rats, on cardiovascular and respiratory variables were studied. Atropine sulphate (10 mg/kg, i.p.) or one puff of atropine nasal aerosol spray (2 mg/puff) was delivered into the tracheal cannula followed by acetylcholine and dichlorvos in the same dose and sequence after 10 minutes. The resultant effects were recorded and analysed. Results: Dose related hypotensive and negative chronotropic action of acetylcholine was potentiated by dichlorvos. However, the respiratory variables were not influenced significantly. Administration of a massive dose of acetylcholine (1 mg, i.v.) after intraperitoneal injection of dichlorvos killed the animals. Ten minutes prior administration of either atropine sulphate (10 mg.kg -1, i.p.) or one puff of atropine nasal aerosol spray (2 mg/puff) completely blocked the hypotensive and negative chronotropic effects of both acetylcholine and dichlorvos. Conclusion: The present study showed that atropine nasal aerosol spray was as effective as parenteral administration of atropine sulphate for protecting against OP poisoning in anaesthetized rats. KEY WORDS Atropine nasal aerosol spray insecticides organophosphorous compounds INTRODUCTION Organophosphorous (OP) poisons inhibit the enzymatic hydrolysis of acetylcholine (ACh) which gets accumulated at nerve endings resulting in prolonged and intensified actions of ACh on the effector site 1,2. Accidental, suicidal and homicidal poisoning is common leading to loss of life all over the world 3. The conventional therapy in most instances is parenteral administration of atropine sulphate to alleviate the effects of excess acetylcholine 4. A majority of deaths due to OP poisoning may be avoided by using atropine sulphate well in time. Due to practical problems i.e. quick administration (intramuscular or intravenous) of atropine sulphate at the site of incidence is difficult in the absence of trained personnel. In the present study, the antidotal efficacy of inhalation of atropine nasal aerosol spray against intraperitoneally administered dichlorvos was examined on certain physiological parameters such as mean arterial blood pressure, heart rate, tidal volume and minute volume in anaesthetized rats. MATERIALS AND METHODS Adult male Wistar rats ( g) were fasted overnight prior to the experiment. The anaesthetized rat Correspondence: Pravin Kumar toxi@drde.8m.com

2 432 PRAVIN KUMAR et al. (1.6 g/kg, i.p. urethane) was dissected in the neck region to cannulate the trachea, right jugular vein and carotid artery. Intravenous administration was done through the jugular vein. The carotid artery was connected to the transducer (Statham, P23DC) filled with heparinized normal saline. The trachea was connected to the pneumotachograph (Fleisch tube). The cardiovascular and respiratory parameters were recorded on a eight channel polygraph (Grass Polygraph, USA, model 7). The heparinized normal saline filled cannula was connected to the transducer and signals from DC Driver amplifier recording were taken from J6 output to EKG Tachograph pre-amplifier, was used for the recording of heart rate. For nasal spray administration, the tracheal cannula was disconnected momentarily from pneumotachograph and the nozzle of the atropine spray bottle was positioned into the tracheal cannula. The manual depression given to plastic nozzle generated one puff of fine aerosol which directly entered into the trachea. After stabilization of blood pressure, heart rate and respiration responses of ACh were taken. Atropine sulphate diluted in normal saline was administered (10 mg.kg -1 ) intraperitoneally or one puff of atropine nasal aerosol spray (2 mg) was given ten minutes prior to administration of ACh or dichlorvos. Atropine Nasal Spray, an amber coloured bottle fitted with a plastic nozzle device capable of generating aerosols during its hand-operated depression. The size and shape of the plastic nozzle was so that it can suitably fit into the human nostrils. The bottle contents were under pressure and depression of the nozzle generated the aerosol. According to the manufacturer (M/s Sudhir Instruments, Hyderabad, India) one puff contained 2 mg of atropine sulphate. In another set of experiment dichlorvos was administered (11 mg.kg -1 calculated as dichlorvos, i.p. equal to 0.5 LD 50 ) and the animal was allowed for one hour for stabilization. As acetylcholine response was potentiated and sustained after the administration of dichlorvos, the next doses of ACh were given only after complete recovery. The following sets of experiments (all in triplicates) were carried out. The sequence of administration of acetylcholine (ACh, 1, 2, 4 µg and 1 mg, i.v., in all the sets), atropine sulphate (Aip, 10 mg.kg -1, i.p.), atropine nasal spray (Asp) and dichlorvos (11 mg.kg -1, i.p. equal to 0.5 LD 50 ) as follows: Set No.1:Control recording ACh Aip ACh. Set No.2: Control recording ACh Asp (1 puff) ACh. Set No.3:Control recording ACh Dichlorvos ACh animal died after 1 mg of ACh. Set No.4:Control recording ACh Dichlorvos ACh Aip ACh. Set No.5:Control recording ACh Dichlorvos ACh Asp (1 puff) ACh. The responses were converted as percent change for each animal and expressed as mean ± SEM. The data were analyzed by one way ANOVA with Dunnett s multiple comparisons. A probability value less than 0.05 was taken as statistically significant. RESULTS Table 1 indicates the effects of acetylcholine (ACh; i.v.) and atropine (i.p. and nasal spray) on blood pressure and heart rate (HR) in anaesthetized and tracheostomised rats. A significant and dose dependent fall in diastolic and decrease in HR was noted with ACh. Massive dose of ACh (1 mg) caused decrease by 25.3% of systolic, 61% of diastolic and 60.9% of HR. Ten minutes pretreatment either with atropine sulphate (Aip) or one puff of atropine nasal spray (Asp) significantly blocked these effects. A remarkable difference of 29.2% between the blocking efficacy of Aip and Asp was seen following administration of 1 mg of ACh on HR. Table 2 depicts effects of various doses of intravenously administered ACh before and after intoxication by dichlorvos, and also the antagonistic effect of Aip and Asp on and HR. Dichlorvos per se caused a significant increase both in systolic (66.1%) and diastolic (97.5%), and after 1 hour of dichlorvos administration a dose related potentiation in the response of ACh was noted i.e. 1, 2 and 4 µg ACh caused 16.8%, 15.4% and 22% decrease in systolic respectively. However, administration of 1 mg ACh after dichlorvos killed the animals. Administration of atropine sulphate (10 mg.kg -1, i.p.) after dichlorvos antagonised the combined parasympathomimetic effects of dichlorvos and higher dose of ACh (1mg). Administration of one puff Asp after dichlorvos also significantly antagonised the parasympathomimetic effects of 1 mg ACh, and prevented death.

3 ATROPINE NASAL SPRAY AGAINST OP POISONING 433 Table 1. Effects of acetylcholine (ACh; i.v.) and atropine (i.p. and nasal spray) on blood pressure () and heart rate (HR) in anaesthetized and tracheostomised rats. S. No. Group n Systolic Diastolic HR 1. Control ACh ± ± 4.9* 70.0 ± ACh ± ± 5.8* 67.6 ± ACh ± 3.3* 58.3 ± 6.1* 63.6 ± 6.4* 5. ACh ± 19.1* 39.0 ± 2.6* 39.1 ± 0.6* After atropinisation by intraperitoneal injection (Aip): 6. Aip (after 10 min) ± ± ± ACh ± ± ± ACh ± ± ± ACh ± ± ± ACh ± ± ± 14.9 After atropinisation by nasal spray (Asp): 11. Asp (after 10 min) ± ± ± ACh ± ± ± ACh ± ± ± ACh ± ± ± ACh ± ± ± 1.0 F P < < < Values are the mean % self control±sem. *Statistically significant from control by Dunnett s test. Control values (taken as 100%): systolic = 102.0±4.6 mm Hg; diastolic = 59.5±3.5 mm Hg; HR=355.9±10.9 beats.min -1 ; Aip = Atropine sulfate, intraperitoneal. Asp = Atropine sulphate nasal spray. ACh-1 = 1 µg; ACh-2 = 2 µg; ACh-4 = 4 µg; ACh-1000 = 1 mg. The other physiological variables viz. tidal volume and minute volume of the rats treated with ACh, dichlorvos, Aip and Asp remained unchanged as compared to that of control group. However, respiratory depression was apparent in the animals those died after administration of dichlorvos followed by higher dose (1 mg) of intravenous ACh (data not shown). DISCUSSION A quick intramuscular or intravenous administration of atropine sulphate at the site of OP poisoning is difficult without trained personnel, a number of deaths ensue, which could have otherwise been avoided. Due to this very reason, in most of the cases of anticholinesterases poisoning the life saving

4 434 PRAVIN KUMAR et al. Table 2. Effects of atropine (i.p. and nasal spray) on acetylcholine (ACh; i.v.) and dichlorvos (11 mg.kg -1, i.p. equal to 0.5 LD 50 ) induced changes in blood pressure () and heart rate (HR) in anaesthetized and tracheostomised rats. S. No. Group n Systolic Diastolic HR 1. Control ACh ± ± ± 6.2* 3. ACh ± ± ± 6.0* 4. ACh ± ± ± 6.4* 5. ACh ± ± 2.6* 39.1 ± 0.6* After 1 hr of dichlorvos administration: 6. Dichlorvos ± 17.8* ± 27.2* 84.3 ± 9.8 (after 1 hr) 7. ACh ± ± ± 11.5* 8. ACh ± ± ± 11.5* 9. ACh ± 11.3* 46.5 ± ± 7.9* 10. ACh Animals died After 1 hr of dichlorvos and atropinisation by intraperitoneal injection (Aip): 11. Aip (after 10 min) ± ± ± ACh ± ± ± ACh ± ± ± ACh ± ± ± ACh ± 2.2* 27.8 ± 5.6* 38.1 ± 0.4* After 1 hr of dichlorvos and atropinisation by nasal spray (Asp): 16. Asp (after 10 min) ± ± ± ACh ± ± ± ACh ± ± ± ACh ± ± ± ACh ± 7.4* 49.3 ± ± 3.0* F P < < < Values are the mean % self control ± SEM. *Statistically significant from control by Dunnett s test. Control values (taken as 100%): (systolic) = 102.0±4.6 mm Hg; (diastolic) = 59.5±3.5 mm Hg; HR = 355.9±10.9 beats.min -1 ; Aip = Atropine sulfate, intraperitoneal. Asp = Atropine sulphate nasal Spray. ACh-1 = 1 µg; ACh-2 = 2 µg; ACh-4 = 4 µg; ACh-1000 = 1 mg.

5 ATROPINE NASAL SPRAY AGAINST OP POISONING 435 potential of atropine sulphate is not fully utilized. It seems reasonable to state that an alternative route and easy method of administration of atropine sulphate is very much required and keeping this point in view the present study was carried out. In OP poisoning if atropine sulphate is administered by inhalation, can directly interact with the respiratory mucosa, thereby reducing the secretion as well as the bronchocon-striction. Now a days there is a general use of aerosols for the management of asthma. Atropine aerosols has been used successfully for a variety of conditions viz., asthma, bronchitis and chronic obstructive pulmonary disease 5. The beneficial effects of atropine inhalation is much better and prolonged compared to the parenteral injection 6. Systemic absorption of atropine is also faster through inhalation. Plasma concentration of atropine was comparable when it was given either as inhalation or as parenteral injection 7. Following intravenous injection of ACh, typical parasympathomimetic effects can be induced for a transient period of time as it is quickly hydrolysed by the action of cholinesterase enzymes 8. However, the transient action of ACh can be sustained and potentiated by prior administration of anticholinesterase 4. Keeping these points in view, in the present study, ACh and dichlorvos were used so as to quickly evaluate the blocking potential of atropine sulphate administered either by intraperitoneal or inhalation route. A sublethal dose of dichorvos which was equal to half of its LD 50 was selected so as to induce maximum cholinomimetic effects but not the death. It is reported that organophosphorous compounds, apart from other effects also cause hypertension and bradycardia 9. Administration of ACh after dichlorvos caused a significant negative chronotropic effect and animals died after administration of higher dose of ACh (1 mg). As expected prior intraperitoneal administration of atropine sulphate completely blocked the muscarinic effects of ACh i.e., hypotension and decrease in HR. Similar protective effects were also noted with animals pretreated with one puff of atropine nasal aerosol spray. Belladona alkaloids including atropine sulphate are absorbed rapidly from gastrointestinal tract and the absorption of atropine sulphate through mucous membranes also occurs readily 10. It is evident from the present findings that the atropine sulphate present in the nasal spray aerosols reached onto mucous membranes and was absorbed satisfactorily to protect against combined cholinomimetic effects of dichlorvos and ACh. Further, atropine sulphate as nasal spray has been found beneficial against methacholine-induced nasal secretions 11. Atropine has a wide safety margin and fatality due to atropine is very rare 10. In the case of doubtful OP insecticide or nerve agent poisoning it is better to give atropine, as the side effects are minimal, transient and may be compromised to the dangers of the OP compounds. Further, the atropine inhalation has greater margin of safety 12. In the present study the atropine aerosol used was for the nasal administration unlike the conventional oronasal route. The use of nasal spray has a definite advantage as this can be administered by an assistant in an unconscious victim and also in the presence of artificial respiration. Though, autoinjectors are in vogue for nerve agent attacks it has several limitations. Training is required for self administration and due to psychological fear sometimes it may not be used properly. Moreover, it is for one time use and for further doses another injector has to be used. The nasal spray may be used repeatedly for several doses and also for several victims. Autoinjectors are expensive and can not be provided for accidents arising from OP insecticides. The present study showed that atropine nasal aerosol spray was as effective as parenteral administration of atropine sulphate for protecting against OP poisoning in anaesthetized rats. ACKNOWLEDGEMENTS The authors are grateful to Dr. R.V.Swamy, Director, Defence R & D Establishment, Gwalior for his encouragement and keen interest in the present study. The authors also thank M/s Sudhir Instruments, Hyderabad, India for providing the atropine nasal spray. REFERENCES 1. Ramesh KP. Organophosphate poisoning. Indian J Clin Practice 1993;3: Namba T. Cholinesterase inhibition by organophophate compound and its clinical effects. Bulletin WHO 1971; 44:

6 436 PRAVIN KUMAR et al. 3. Tripathi KD. Essentials of Medical Pharmacology. 4th ed. New Delhi: Jaypee Brothers; Taylor P. Anticholinesterse agents. In: Gilman AG, Rall TW, Nies AS, Taylor P, editors. Goodman and Gilman s The Pharmacological Basis of Therapeutics. 8th ed. New York: Pergamon Press; p Lew DB, Herrod HG, Crawford LV. Combination of atropine and isoetharine aerosol therapy in pediatric acute asthma. Ann Allergy 1990;64: Gillett MK, Snashall PD. Measurement of pharmacological antagonism produced by atropine in bronchi of normal and asthmatic subjects. Eur Respir J 1988;1: Kradjan WA, Lakshminarayan S, Hayden PW, Larson SW, Marini JJ. Serum atropine concentration after inhalation of atropine. Am Rev Respir Dis 1981;123: Taylor P. Cholinergic agonists. In: Gilman AG, Rall TW, Nies AS, Taylor P, editors. The Pharmacological Basis of Therapeutics. 8th ed. New York: Pergamon Press; p Dube SN, Pravin Kumar, Kumar D, Das Gupta. Route-specific cardiorespiratory and neuromuscular changes following organophosphorous poisoning in rats. Arch Int Pharmacodyn 1993;321: Innes IR, Nickerson M. Atropine, scopolamine, and related antimuscarinic drugs. In: Goodman LS, Gilman A, Gilman AG, Koelle GB, editors. The Pharmacological Basis of Therapeutics. 5th ed. New York: Macmillan Publishing Co., Inc.; p Kaiser HB. Duration of action of intranasal atropine on methacholine-induced nasal secretions. Arch Otolaryngol Head Neck Surg 1996;122: Wilston SJ, Gravelyn, Sitrin RG. Prevention of bradycardic responses to endo-tracheal suctioning by prior administration of nebulized atropine. Crit Care Med 1987;15: CME : OMEGA-3 FATTY ACIDS IN HEALTH AND DISEASE Friday, 4 th January 2002 For further details please contact : Dr. Mrs. S.D. KULKARNI Organizing Secretary, CME : Omega-3, Professor & Head, Department of Pharmacology, Bharati Vidyapeeth Medical College, Katraj Dhankawadi, Pune Maharashtra, INDIA. sdk_cme@yahoo.com Phone : (O) , (R) Fax : (O)