ABSTRACT Introduction: Zidovudine and Efavirenz are anti HIV drugs which are used in pregnancy to prevent maternal to child transmission. Material and Methods: Zidovudine and Efavirenz are given separately as well as together in dose of 50mg/kg to pregnant mice and its effect on fetal toxicity was recorded by measuring number of implants , live fetuses , resorption in a single mice. Weight of the fetus as well as its crown rump length was also recorded. Observation: There is decrease in number of implants, live fetus and increase in resorption from group I to IV. Also there is decrease in fetal weight and crown rump length from group I to IV. Conclusion: There is fetal toxicity induced by Zidovudine and Efavirenz and thus should be used with caution in 1st trimester of pregnancy ORIGINAL RESEARCH PAPER Anatomy ZIDOVUDINE AND EFAVIRENZ INDUCED FETAL TOXICITY IN SWISS ALBINO MICE KEY WORDS: INTRODUCTION Acquired immune deficiency syndrome (AIDS) is characterised by destruction of the host immune system, resulting in the development of opportunistic infections, rare neoplasm and death. The aetiological agent responsible for AIDS is the human immunodeficiency virus which can be transmitted congenitally, parenterally and by sexual contact. Use of antiretroviral drugs during pregnancy has increased since the demonstration of reduction of mother to child transmission (MTCT) of HIV-1 first with zidovudine monotherapy and more recently with highly active retro viral therapy regimens (HAART). Based on these recommendations many women are receiving HAART and may enter pregnancy already receiving multiple antiretroviral agents. Zidovudine (3-azido-3-deoxythymidine) is a synthetic thymidine analog with potent in vitro activity against a broad spectrum of retroviruses including HIV-1, HIV-2, and human T-cell 1 lymphotrophic viruses (HTLV) I and II. Zidovudine acts as against HIV virus by inhibiting its viral reverse transcriptase and by 2 inhibiting its viral DNA chain elongation. It is a constituent of HAART(Highly active antiretroviral therapy) used for preventing Maternal to child transmission(MTCT).It is classified as class C drug which means that it was found safe in animal studies but studies in human are inconclusive. Zidovudine has been demonstrated to be genotoxic in humans and exerts a dose related decrease of cell proliferation and differentiation, cytotoxic effects, metabolic disruption, increased cell mortality and mtDNA depletion on 3,4,5 human cells in vitro Efavirenz is non nucleoside reverse transcriptase inhibitor which binds to reverse transcriptase resulting in allosteric inhibition of RNA dependent DNA polymerase. Efavirenz has been classified as a class D drug (evidence of risk, use only when potential benefits st outweigh the risk). Use of Efavirenz in 1 trimester has shown to cause neural tube defects (anencephaly, Dandy Walker syndrome) and facial defects like microopthalmia, anopthalmia and cleft 6,7 palate in Cynomolgous monkey. The study is done to evaluate the risk benefit ratio of Zidovudine and Efavirenz as they are used as fixed dose combination to prevent maternal to child transmission of HIV virus during pregnancy MATERIAL AND METHODS Prior approval of Central Animal Ethical committee, IMS, BHU was taken before the start of this study. The study was carried out on Swiss Albino female mice of 3 months of age weighing 20-25 g, which were caged in air conditioned animal house of the Department of Anatomy. Animals were kept in polypropylene cage floored with paddy husk to provide them bed. Animals were provided with animal feed and water ad libitum maintained in 12 h 0 light/dark cycles at 26 ± 2 C. Female mice were kept in mating with male mice in the ratio of 2:1 overnight and were inspected next morning for the presence of vaginal plug. The day of vaginal plug seen was considered as day 0 of gestation (GD 0). Weight of each female mice was taken on GD 0 and placed in an individual cage. Pregnant Swiss albino mice had been divided into following three groups Control group (I): Mice treated with distilled water Group II: Mice treated with Zidovudine (ZDV) Group III: Mice treated with Efavirenz( EFV) Group IV : Mice treated with ZDV+EFV Group II was given ZDV in the dose of 50 mg/kg from day 6-15 of gestation by oral gavage. Similarly Group III was given EFV in the dose of 50 mg/kg again from 6-15 day of gestation by oral route. Group IV was given combined therapy of ZDV and EFV in the dose Dr Anand Mishra Professor, Department of Anatomy, Institute of Medical Sciences, Banaras Hindu University www.worldwidejournals.com 123 Dr Rakesh Gupta* Professor, Department of Anatomy, Rohilkhand Medical College, Bareilly *Corresponding Author Dr Amit Kumar Nayak Assistant Professor, Department of Anatomy, Institute of Medical Sciences, Banaras Hindu University Dr Kapil Kumar Malviya Assistant Professor, Department of Anatomy, Institute of Medical Sciences, Banaras Hindu University Dr Sashikant Pandey Professor, Department of Anatomy, Institute of Medical Sciences, Banaras Hindu University Dr Surendra Kumar Pandey Assistant Professor, Department of Forensic Medicine, Institute of Medical Sciences, Banaras Hindu University Dr Sashikant Verma PARIPEX - INDIAN JOURNAL OF RESEARCH Volume-7 | Issue-7 | July-2018 | PRINT ISSN No 2250-1991