Cetin, Nazmi

Emre, B.

Sagmanligil, V.

Sireli, M.

Guinea pigs were used to observe the possible side effects of ivermectin (500 μg/kg b.w.) on the heart by  recording their electrocardiograms (ECG) at 24, 48 and 72 hours after its injection (experimental groups).  Significant effects of ivermectin on the electrocardiographic parameters belong to limb lead II were compared  to those of the control group. These were: the increases in amplitudes of P, S (only at 24 hours) and  T waves, and also the lengthening (or “prolongation”) in the durations of P and T waves, QRS complex  (only at 24 and 48 hours) and PR and QTc intervals at 24, 48 and 72 hours. As a consequence of the prolonged  durations mentioned above, statistically significant decreases of heart beats were found on the electrocardiograms  recorded at 24 and 48 hours after ivermectin injection (p&lt;0.05). In conclusion, the weak  conductance in the heart of guinea pigs as an indicator of the prolongation in durations and intervals (negatively  dromotropic) induced by ivermectin can be interpreted as its inhibitory effect on the sarcoplasmic  reticulum Ca2+ -ATPase pump causing a late Ca2+ accumulation after systole due to the reduced amount of  Ca2+.

Sireli, M

Sagmanligil, V

Çetin, N

Emre, B

Journals from University of Tartu

IntroductionIvermectin has been used against many endopara-sitic and ectoparasitic species in all domestic ani-mals for almost two decades and in humans for thetreatment of certain filarial tropical diseases (Fisher& Helmut, 1992). The effects of ivermectin arebased on the glutamate-gated CI- channel that hasonly been found in certain invertebrates includingnematodes (Martin et al., 1997). Although iver-mectin is well tolerated in both human and animal,toxic effects may appear after using high doses(Doody, 1997). Some dog breeds, like the Collie,seem to be more susceptible to ivermectin toxicity.Common symptoms of ivermectin toxicity are vom-iting, depression, mydriasis, ataxia, blindness, comaand sometimes death (Edwards, 2003). The use ofivermectin in the treatment of ectoparasitism in rab-bits and guinea pigs has been studied by Mc Kellaret al. (1992).Unfortunately few investigations about the sideeffects of ivermectin on the hearts of animals wereconducted and they showed negative effects such asbradycardia in dogs (Button et al., 1988) and tachy-cardia in calves Basudde, 1989). The purpose ofthis electrocardiographic study is to examine thepossible side effects of ivermectin on the heart ofguinea pigs secondary to its common use in domes-tic animals for the treatment of ectoparasitism.Materials & MethodsTen male albino guinea pigs (Dunkin Hartley, RefikSaydam Hygiene Center, Ankara, Turkey) eachweighing 300-350 g were used in this study. Theywere given food (Pellet, Purina, Istanbul,Turkey)and water ad libitum. Any anaesthetics were notapplied during the processes. The limb leads wereapplied by means of a specially designed plateimmobilising the animal in the supine position andScand. J. Lab. Anim. Sci. 2008 Vol. 35 No. 1Published in the Scandinavian Journal of Laboratory Animal Science - an international journal of laboratory animal scienceElectrocardiographic Changes Induced by Ivermectin in Guinea Pigsby M. Şireli1, V. Sağmanligil1, N Çetin2,* &  B. Emre11Department of Physiology, Veterinary Faculty, Ankara University, Ankara, Turkey2Department of Physiology, Veterinary Faculty, Erciyes University, Kayseri, TurkeySummaryGuinea pigs were used to observe the possible side effects of ivermectin (500 µg/kg b.w.) on the heart byrecording their electrocardiograms (ECG) at 24, 48 and 72 hours after its injection (experimental groups).Significant effects of ivermectin on the electrocardiographic parameters belong to  limb lead II were com-pared to those of the control group. These were: the increases in amplitudes of P, S (only at 24 hours) andT waves, and also the lengthening (or “prolongation”) in the durations of P and T waves, QRS complex(only at 24 and 48 hours) and PR and QTc intervals at 24, 48 and 72 hours. As a consequence of the pro-longed durations mentioned above, statistically significant decreases of heart beats were found on the elec-trocardiograms recorded at 24 and 48 hours after ivermectin injection (p<0.05). In conclusion, the weakconductance in the heart of guinea pigs as an indicator of the prolongation in durations and intervals (neg-atively dromotropic) induced by ivermectin can be interpreted as its inhibitory effect on the sarcoplasmicreticulum Ca2+ -ATPase pump causing a late Ca2+ accumulation after systole due to the reduced amount ofCa2+. *Correspondence: Nazmi Çetin, Assoc. Prof. Dr.Department of Physiology, Veterinary Faculty, ErciyesUniversity, 38090 Kocasinan, Kayseri, Turkey.Tel: +90 352 338 00 06Fax: +90 352 337 27 40E-mail: cetin@erciyes.edu.tr45Scand. J. Lab. Anim. Sci. 2008 Vol. 35 No. 146enabling good contact between three active elec-trodes and the neutral electrode with the limbs ofthe animal (Cieślar et al., 1986). A better contactbetween electrode surface and the skin of the limbwas achieved by moistening the limb with gel (Ber-kim, Sonotact, Ultrasound Jell). Electrocardio-graphic recordings were made using CardiofaxECG-6851 K (Nihon Kohden, Tokyo, Japan) at thespeed of 50 mm/sec  and sensitivity of 1 mV = 1cm.  Electrocardiograms of the animals were firstrecorded before any injection (control group). Theythen received a subcutaneously injection of iver-mectin (Ivomek–Topkim Drug Co Ltd, Turkey) atthe dose of 500 µg/kg b.w. and the electrocardio-gram was recorded at 24, 48 and 72 hours afterinjection (experimental group).Quantitative measurements such as; heart rates,amplitudes of P, R, S and T waves, duration of P andT waves, QRS complex and finally duration of PRand QTc (Corrected QT) (Piotrovsky, 2005) inter-vals were evaluated from limb lead II.The control animals data were statistically com-pared with those from the experimental groupsrecorded at 24, 48 and 72 hours after injection ofivermectin and the experimental groups data werealso compared together using repeated measuresanalysis of variance (Mendenhall, 1971). Meanswere considered significantly different at p< 0.05.Data were expressed as means ± SEM.ResultsMeasurements in limb lead II belong from the con-trol animals and ivermectin (500 µg/kg b.w.) inject-ed animals recorded at 24, 48 and 72 hours afterinjection are presented in Table 1. Representative electrocardiograms from guineapigs prior to drug injection (A), and 24 (B), 48 (C)and 72 hours (D) after injection are shown in Fig 1.Table1. The electrocardiographic parameters of limb lead II taken before (control group) and after iver-mectin (500 µg/kg b.w.) injection at 24, 48 and 72 hours (experimental groups) in the guinea pigs (n=10).Data were given as mean± SEM. Parameters Control           After drug administration         24 h                           48 h                         72 h P wave duration (sec)   0.025 ± 0.002a    0.043 ± 0.005b    0.048 ± 0.004b  0.040 ± 0.003 bP wave amplitude (mV)   0.150 ± 0.011a     0.210 ± 0.007b    0.205 ± 0.017b   0.195 ± 0.016 bPR interval duration (sec)    0.050 ± 0.002 a    0.064 ± 0.003 b    0.065 ± 0.002b   0.060 ± 0.001bQRS comp. duration (sec)     0.018 ± 0.001a    0.027 ± 0.003b   0.028 ± 0.003b    0.023 ± 0.002 R wave amplitude (mV)     0.560 ± 0.047    0.620 ± 0.042      0.670 ± 0.052    0.601 ± 0.066 S wave amplitude (mV)  0.085 ± 0.010a    0.195 ± 0.036 b    0.155 ± 0.026     0.155 ± 0.024 T wave duration (sec)  0.024 ± 0.003a     0.043 ± 0.003 b    0.051 ± 0.004b  0.044 ± 0.003 bT wave amplitude (mV)     0.105 ± 0.016a     0.191 ± 0.024 b    0.185 ± 0.018b  0.160 ± 0.016 bQTc interval duration(sec)   0.274 ± 0.0028a    0.313 ± 0.0035b  0.309 ±0.0031c  0.296 ± 0.034 dHeart rate (beat/min)         274.50 ± 13.4a       243.80 ± 7.1b    243.00 ± 5.8b    251.40 ± 7.4p<0.05: different letters in the same line indicate significant differences. Scand. J. Lab. Anim. Sci. 2008 Vol. 35 No. 1The amplitudes and duration of P and T waves atthree different times after ivermectin injection werestatistically higher than those from the controlgroup (p<0.05).The comparison of the amplitude of the S wavesshowed that they were significantly (p<0.05) higherin the 24h-experimental group compared to con-trols. The S wave amplitudes measured 48 and 72hours after injection were higher than that of thecontrol group but the difference was not statistical-ly significant.The duration of PR and QTc intervals lengthenedwhen examined at 24, 48 and 72 hours after iver-mectin injections and were statistically longer(p<0.05) than that of the control group. In additionthere were significant decreases (p<0.05) in theQTc duration recorded at 72 hours compared tothose obtained at 24 and 48 hours.Regarding QRS complex duration, statistically sig-nificant differences were seen only between thecontrols and those animals recorded at 24 and 48hours after injection (p<0.05). The heart rate wassignificantly (p<0.05) decreased at 24 and 48 hoursafter ivermectin application compared to the  con-trol group. DiscussionIn this study, one single dose of 500 µg/kg b.w. iver-mectin was administered subcutaneously to guineapigs, as studied by McKellar et al. (1992) who werelooking for the clinical and pharmacological char-acteristics of ivermectin. Recording time of theelectrocardiograms was set at 24, 48 and 72 hoursafter injection since the maximum effectiveness ofthe drug in the plasma of guinea pigs was found tobe at 72 hours (Mc Kellar et al., 1992). However,the results here showed that significant differencesin the electrocardiographic values were mainly seenat 24 and 48 hours after ivermectin injections. Inaddition, the reason for not using any anaestheticsin this research was their negative effects such as alengthening in the duration of P wave, PR and QTintervals and a decrease in the duration of QRScomplex (Pişkin et al., 1999).The electrocardiographic data obtained from thecontrol group showed similar patterns to those pub-lished by Cieślar et al. (1986). The differences inthe duration and amplitude of P and T wavesobserved at each of the three times after injection(24, 48 and 72h) compared to those of the controlgroup meant the changes in illustrate transmissioncaused by the drug. The increase in amplitude andprolongation in duration of the P wave can be inter-preted as having a strengthened systole and return-ing to the late depolarisation respectively.Moreover, it would be interesting to observe thechanges in cellular Ca2+ level, which is regulatedduring normal contraction-relaxation cycle, espe-cially in cardiac myocytes since they are considered47Figure 1. Representative electrocardiograms (limbleads II) of guinea pigs prior to treatment with iver-mectin (A), and at 24 (B), 48 (C) and 72 hours (D)after treatment. (standardization, 1mV= 10 mm;chart speed, 50 mm/s).Scand. J. Lab. Anim. Sci. 2008 Vol. 35 No. 148to play an important role in both mechanical dys-function and arrythmogenesis associated with con-gestive heart failure (Bers, 2000). There have beenvarious studies showing a decline in cardiac forcedue to a decreased Ca2+ sensitivity of the myofila-ments and/or a deterioration of the Ca2+ signals(Niggli, 1999). During membrane depolarisation,Ca2+ flows across the membrane into the cardiacmuscle fiber after being regeneratively releasedfrom the sarcoplasmic reticulum causing anincrease in the concentration of free Ca2+ in themyoplasm (Reuter, 1974).It can be suggested that, the inhibitory effect ofivermectin, like several macrocyclic lactone com-pounds (i.e. tacrolismus (FK506), ascomycin,rapamycin), on the sarcoplasmic reticulum Ca2+ -ATPase (SERCA) pump (Ahern et al., 1999;Bultynck et al., 2000) is a crucial point in explain-ing the changes of the contraction-relaxation cyclesince SERCA was shown to be one of the mostimportant transporters which remove Ca2+ from thecytosol (Bers, 2000). Thus, the reason of the pro-longed and enlarged depolarisation with a late Ca2+accumulation after systole (Frank et al., 2002)might possibly be the result of the reduced amountof Ca2+ secondary to the decreased activation ofSERCA. Similarly, the late loading of Ca2+ duringsystole would also be seen by the removing of Ca2+during diastole (T wave), again because of thedecreased activation of SERCA. According to our results, vermectin significantlychanged all ECG parameters after 24h except the Rwave amplitude and this effect continued at 48h and72h for most of them although they tended to revertto the control level McKellar et al. (1992) foundthat the level of ivermectin in the plasma was max-imum at 72h and lower then in other species; theyalso mentioned that the differences in metabolismof ivermectin in guinea-pigs were either more rapidor slower than the others. Considering their meas-urement, which was only done at 72h for guinea-pigs, and other literature like Minematsu et al.(1999, 2001) showing that FK506, which is amacrocyclic lactone similar to ivermectin causedQTc lengthening and reached the maximum level at90 mins. in whole blood and plasma as well as ven-tricular myocytes; however, it was decreased inplasma and whole blood rapidly while was continu-ing to effect the myocardium. This was probably thelogical explanation of the sustained effect of iver-mectin on some ECG parameters found in thisstudy after 72h.In this research, the lengthening of PR and QTcintervals and duration of P and T waves, and alsothe decrease in the heart rate, might be the indicatorof the weak conductance (negatively dromotropic)depending on ivermectin-caused hyperpolarizationby opening the chloride channels. There are severalreferences showing various ivermectin receptors inmammalian and invertebrates (Fisher & Helmut,1992). Opening the glutamate-gated Cl– channels isthe only certain known mechanism of ivermectin(Cully et al., 1994), although this can not be themechanism seen here due to the absence of thesechannels in vertebrates (Gerard et al., 2000).Although its efficacy and easy use at different dosesand routes in guinea pigs were reported by Webb(1992), its toxicity in the rodents (Campbell, 1989)and the negative effects of ivermectin on the heartof guinea pigs suggested in this research must betaken into consideration while evaluating its safetywhen using this drug even at treatment doses. ReferencesAhern GP, PR Junankar, SM Pace, S Curtis, JAMould & AF Dulhunty. Effects of ivermectinand midecamycin on ryanodine receptors andthe Ca2+ -ATPase in sarcoplasmic reticulum ofrabbit and rat skeletal muscle. J Physiol, 1999,514, 313-326.Basudde CD. Clinical signs and biochemicalchanges in calves caused by injection of iver-mectin. Vet Quart, 1989, 11, 29-32.Bers DM. 2000. Calcium fluxes involved in controlof cardiac myocyte  contradiction. Review CircRes, 2000, 18, 275-281.Bultynck G, PD Smet, AF Weidema, MV Heyen, KMaes, G Callewaert, L Misslaen, JB Parys &Scand. J. Lab. Anim. Sci. 2008 Vol. 35 No. 149HD Smedt. Effects of the immunosuppressantFK 506 on intracellular Ca2+ release and Ca2+accumulation mechanisms. J Physiol, 2000,523, 681-693.Button C, R Barton, P Honey & P Rickford.Avermectin toxicity in calves and evaluation ofpicrotoxin as an antidote. Aust Vet J, 1988, 65,157-158.Campbell WC. Ivermectin and Abemectin.Springer-Verlag, New York. 1989, 89-112.Cieślar G, A Sieron, E Rzepka, J Zmudzinski & AFranek. 1986. Normal electrocardiogram inguinea pig. Acta Physiol Pol, 1986, 37, 139-149.Cully DF, DK Vassilatis, KK Liu, PS Paress, LHTVanderploeg, JM Schaeffer & JP Arena.Cloning of an avermectin-sensitive glutamate-gated chloride channel from caenorhabditis ele-gans. Nature, 1994, 371, 707-711.Doody GM. Avermectin toxicity in the dog. Vet Rec,1997, 7, 611-612.Edwards G. 2003. Ivermectin: does P-glycoproteinplay a role in neurotoxicity. Review. Filaria J,2003, 2, Suppl 1, 8-9. Fisher MH & M Helmut. The chemistry and phar-macology of avermectins. Annu Rev PharmacolToxicol, 1992, 32, 537-553.Frank KF, B Bolck, K Brixius, EG Kranias & RHSchwinger. Modulation of SERCA: implica-tions for the failing human heart. Basic ResCardiol, 2002, 97, 172-178.Gerard RD, KA Wafford, A Smith, GR Marshall, PJBayley, JM Schaeffer, PT Meinke & RMMckernan. Anticonvulsant and adverse effectsof avermectin analogs in mice are mediatedthrough the y-aminobutyric acid receptor. JPharmacol Exp Ther, 2000, 295, 1051-1060.Martin RJ, AP Robertson, & H Bjorn. Target sites ofanthelmintics. Parasitology, 1997, 114, 111-124.Mc Kellar QA, DM Midgley, EA Galbraith, EWScoot & A Bradley. Clinical and pharmacologi-cal properties of ivermectin in rabbits andguinea pigs. Vet Rec, 1992, 25, 71-73.Mendenhall WS. Introduction to probability and sta-tistics, third edition. Belmont: WadsworthPublishing Co. Inc. 1971.MinematsuT, H Ohtani, H Sato & T Iga. SustainedQT prolongation induced by tacrolismus inguinea pigs. Life Sciences, 1999, 65, 197-202.MinematsuT, H Ohtani, Y Yamada, Y Sawada, HSato & T Iga. Quantitative relationship betweenmyocardial concentration of tacrolismus andQT prolongation in guinea pigs:Pharmacokinetic/pharmacodynamic modelincorporating a site of adverse effect. Journal ofPharmacokinetics and Pharmacodynamics,2001, 28, 533-554.Niggli E. Ca2+ Sparks in cardiac muscle: is there lifewithout them? News. Physiol Sci, 1999, 14,129-134.Piotrovsky V. Pharmacokinetic-pharmacodynamicmodeling in the data analysis and interpretationof drug-induced QT/QTc prolongation. TheAAPSJ, 2005, 7, 609-624.Pişkin I, M Ş ireli1, V Sağmanligil & B Emre. Theeffects of some anaesthetics on electrocardio-grams of guinea pigs. Tr J Vet Anim Sci, 1999,23,  161-166.Reuter H. Exchange of calcium ions in mammalianmyocardium. Brief Reviews. Circ Res, 1974,34, 599-605.Webb RA. Ivermectin in guinea pigs. Vet Rec, 1992,4, 307.

Electrocardiographic changes induced by ivermectin in guinea pigs

Abstract

Similar works

Full text

Available Versions

Journals from University of Tartu

Erciyes University - AVESIS