termination of pregnancy in bitches - Jivaonline.net

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GENERAL ARTICLEprolong oviductal retention of embryos and secondlyoestrogen has direct degenerative effects on ova andmay alter the endometrium.1. OESTROGENSOestrogens are widely used to preventunwanted pregnancies. They act by altering thetransport time of zygotes and thus interfering withimplantation. In some bitches estrogens given duringoestrus results in early luteolysis and this effect maybe mediated either directly upon luteal progesteroneproduction or by inhibition of LH release which isluteotrophic.a. Diethyl Stilbesterol (DES)Injection of DES at a dose rate of 2mg/kgbody weight, up to 25mg once or twice within 5 daysof mating is found to be highly effective interminating pregnancy. However injectable DES isnot available for veterinary practice. Oral DES hasbeen recommended at a dosage of 1 to 2 mg/day for 7days after mating, but oral therapy has not been foundto be completely reliable.b. Oestradiol cypionateIt was an oestrogen compound commonlyused by veterinarians for the management ofunwanted mating. The treatment protocol involved isadministration of 0.25 to 1 mg total dose within 3days of mating. A dose rate of 0.04 mg /kg is 100percent successful in preventing pregnancy inbitches. The total dose should not exceed 1mg.Despite the potentially favourable action ontermination of pregnancy, it has major side effectssuch as permanent bone marrow suppression ordestruction resulting in severe anaemia, leukopenia,thrombocytopenia and death.c. Conjugated oestrogenConjugated oestrogens can be used for thetreatment of misalliance in dogs within 5 daysfollowing breeding. They are mainly isolated frommare's urine and hence it can be called as conjugatedequine oestrogen. Most commonly used for thetreatment of osteoporosis, atrophic vaginitis,atrophic urethritis etc as a complication ofmenopause in woman. Commonly availablepreparation is PREMARIN 0.625mg and 1.25mgtablets. Dosage 1.875mg daily for 3 daysHowever estrogens can result in thedevelopment of pyometra by causing cervicalrelaxation thus allowing the vaginal bacteria to enterthe uterus. Estrogens may also produce dose relatedbone marrow suppression. Diethyl stilbesterol,oestradiol benzoate and estradiol cypionate havebeen widely used to prevent implantation.But oestrogen preparations are notrecommended in veterinary practice because of theirharmful side effects. Oestrogen is thought topredispose pyometra in bitches by sensitizingprogesterone receptors and enhancing binding ofprogesterone to the endometrium. It has been alsoreported that excess serum estrogens can lead tooestrogen- induced bone marrow destruction.2. PROSTAGLANDINS ANDITS ANALOGUESPregnancy in the bitch depends onprogesterone secretion from corpora lutea. Manystudies indicate that bitches that have corpora luteaare relatively resistant to the luteolytic effects ofprostaglandins during the first 14 to 28 days ofpregnancy. PGF2 (Natural Prostaglandins ieDinoprost) is luteolytic and uterotonic, inducingintense uterine contractions due to the smoothmuscle contraction effects and may lead to adversereactions. Synthetic analogs (cloprostenol sodium)characterized by more specific activity on the corpusluteum and less on smooth muscle stimulationproperties have fewer side effects.A. Natural Prostaglandin: - Prostaglandins arefound to be highly effective for termination ofpregnancy in bitches after 30 days of gestation. Itsuse prior to 30 day is not recommended. Mostpreferred treatment protocol is 0.1 mg/kg s/c every 8hours for 2 days and then 0.2 mg/kg given s/c every 8hours until abortion complete, the average wasJIVA Vol. 10 Issue 1 April 201261
GENERAL ARTICLEJ. Ind. Vet. Assoc., Kerala. 10 (1)approximately 5-7 days (Feldman et.al, 1993 andRenukaradhya et.al, 2008). This protocol resulted inthe least side effects. After administration of drug,the dog should be observed for 30 minutes for anyside effects. The dog should be fed 1-2 hours afterprostaglandin injection so as to avoid vomiting. It hasbeen observed that plasma progesterone less than 2.0ng / ml result in pregnancy termination and pretreatment concentration of plasma progesterone ismore than 6ng/ml (Feldman et.al, 1993). Most of theanimals treated will exhibit some of the followingside effects like panting, respiratory distress, excesssalivation, vomiting, defecation, stranguria andurination. Normally these side effects start within 30seconds to 3 minutes and usually persist for 5-20minutes. Side effects are usually severe during thefirst few injections and side effects will bediminishing after each subsequent injection.Preparation - LUTALYSE 5ml &10ml vials areavailable. Concentration 5mg/mlb. Prostaglandin analogs:- It has greater luteolyticeffectiveness at relatively low doses and decreasesthe occurrence of myometrial contractions andseverity of side effects compared to naturalprostaglandins. It has much greater affinity for theprostaglandin receptors and has a longer half life thannatural prostaglandin. It can be given at the dose rateof 2.5µg/Kg body weight subcutaneously every 48hours for 3 to 4 times (Reddy et.al, 2010). In order toreduce the side effects atropine sulphate can be givenat the rate of 0.04 mg/kg body weight subcutaneously10-15 minutes prior to the administration of drug.Preparation Inj.Clostenol 2ml, Inj.Pragma2ml,Inj.Cyclix 2ml, Inj. Estropur 2ml Concentration-250µg/ml3. DOPAMINE AGONISTSDopaminergic agonists are ergotinederivativealkaloid compounds that exert an antiprolactinergiceffect. The ability of dopamineagonists to inhibit prolactin secretion makes themoptimal for milk suppression, either during overtpseudopregnancy episodes or in the post-partumperiod. It is well known that prolactin is a requiredluteotropic hormone during the second half of canineluteal phase. Therefore, anti-prolactins can also beused to suppress luteal function in progesteronedependent conditions such as pyometra, unwantedpregnancy and mammary tumors. Two of the mostwidely used dopamine agonists in dogs arebromocriptine and cabergoline, which have a directaction on D2-dopamine receptors of the lactotrophiccells of the anterior pituitary gland.a. Bromocriptine: - It has been reported to be aneffective abortifacient after 35 days of gestation butnot prior to day 30. Two different treatment protocolshave been adopted. In one protocol 0.1mg/kg bodyweight daily or BID for 6 consecutive daysbeginning on day 30 of gestation. In the secondprotocol, 0.03 mg/kg twice daily for 4 daysbeginning after day 30 of gestation. Bromocriptinecommonly causes inappetence, anorexia, vomitingand depression. Also the drug is not 100% effectivein terminating pregnancy. Emesis is presumably dueto interaction with dopaminergic elements in theemesis centre of the brain and the ability of the drugto cross the blood brain barrier. The emetic effectmay reduce the absorption of the total doseadministered, and thus compromise efficacy.Because of above reasons the drug has not been usedextensively. Preparation ENCRIPT 2.5 mg tab,PROCTINAL 1.25 & 2.5 mg tabs.b. Cabergoline: - It is a long acting dopaminereceptor agonist and prolactin inhibitor. It is highlyeffective orally and parenterally. A dose of 5µg/kgonce daily cause a sharp decline in serum prolactinconcentration and result in abortion without muchside effects (Reddy et.al, 2010).. The side effects ofcabergoline are milder (compared to those ofbromocriptine) presumably due to the fact that itappears to be a more specific D-2 dopamine receptoragonist and is less able to cross the blood-brainbarrier and have CNS effects.Preparation CABGOLIN Tab 0.25 & 0.5mg, CAMFORTE Tab 0.5 & 1mg62
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