Nära relation mellan människor och sällskapsdjur har många fördelar. Men det finns risk för överföring av zoonotiska parasiter. Hittills finns det inga praktiska metoder för att minimera antalet ägg i miljön, så antiparasitära medel är fortsatt ett värdefullt verktyg. De förekommer i många olika beredningsformer, varumärken och olika kombinationer av substanser. Men hur säkra och effektiva är egentligen de här substanserna som finns ute på marknaden? I detta litteraturarbete har fokus lagts på en ny kombination av ett endo- och ekto- antiparasitärt medel i syftet att utvärdera hur effektivt och säkert det är mot gastrointestinala nematoder hos hundar. Läkemedlet heter NexGard Spectra®  och innehåller det anthelmintiska medlet, milbemycinoxim och en insekticid substans, afoxolaner. Arbetet har omfattat en litteratursökning och granskning av publicerade forskningsresultat från 12 olika länder. Fyra kvantitativa studier som analyserade effekt av afoxolaner i kombination med milbemycinoxim valdes som grund till arbetet. Resultat av litteraturstudien visar att tuggtablett NexGard Spectra®  har en adekvat reducerande effekt mot ett brett spektrum av parasitiska nematoder hos hundar. Det är en säker och effektiv behandling. Inga interaktioner mellan de två aktiva substanser eller negativ påverkan på djurens hälsa har rapporterades. Denna kunskap kan användas vid klinisk behandling av gastrointestinala nematodinfektioner hos hundar, vid samtidigt ekto- och endoparasitangrepp. / Research have shown positive effects of close relationships between humans and pets also known as the human-animal bond. Companion animals not only can influence socialization and mental abilities positively, but also improve physical well-being. Alongside of these advantages there are some zoonotic hazards which mustn't be underestimated. Drug treatment to reduce parasites has been used since anti parasitic substances were introduced in the mid-1900s. Now there are many different products, in different forms and in a variety of compounds. As studies haven’t shown any practical methods to minimize the level of eggs in the environment and prevent contamination, antiparasitic agents are our most important tool to control parasites and consequently to improve animal and public health. This thesis focuses on a quite new combination of an endo- and ectoparasite agent. NexGard Spectra®  contains the anthelmintic agent milbemycin oxime, combined with an insecticidal substance, afoxolaner. The aim of this literature work was to investigate how effective and safe this “combination” is against gastrointestinal nematodes in dogs. This study is a literature review. Articles were selected from PubMed article database, Primo and Science Direct after searches with different key terms. Through different combinations of keywords scientific articles that coordinated with the studies aim were selected for critical appraisal. A series of studies about efficacy of NexGard Spectra®  which were conducted in a wide range of different countries such as USA, South Africa and some countries in Europe have been analyzed. Five randomized double-blind studies are chosen as a basis for the thesis. Furthermore, an overview of the Swedish Board of Agricultures report on drugs sale for treatment of animals is also included. The results of the literature reviews show that NexGard Spectra®  chewable tablet, containing the two substances milbemycin oxime and afoxolaner, is a safe and effective treatment for dogs who are infected with a wide range of nematodes. No pharmacological interaction between the two active substances or serious negative influence on animal health has been reported. Detection of parasite occurrence has showed high efficacy of the product against most gastrointestinal nematodes. Conclusions that can be drawn from this study are that NexGard Spectra®  can be considered as a safe and effective treatment against gastrointestinal nematodes in dog. The fact that nematode infections in dogs could be prevented or treated by NexGard Spectra® can be just because of the endoparasitic substance, milbemycine oxim. Nevertheless, because NexGard Spectra®  is basically an anti endo- ectoparasite product, its efficacy against both endo- and ectoparasites requires better methods to analyze and determine efficacy of  NexGard Spectra® against both endo and ectoparasites and clearer guidelines to justify usage of it.