The slight mobility of these arches when weight is applied to and removed from the foot makes walking and running more economical in terms of energy. As can be examined in a footprint, the medial longitudinal arch curves above the ground. This arch stretches from the heel bone over the "keystone" ankle bone to the three medial metatarsals. In contrast, the lateral longitudinal arch is very low. With the cuboid serving as its keystone, it redistributes part of the weight to the calcaneus and the distal end of the fifth metatarsal. The two longitudinal arches serve as pillars for the transverse arch which run obliquely across the tarsometatarsal joints. Excessive strain on the tendons and ligaments of the feet can result in fallen arches or flat feet. Muscles
The muscles acting on the foot can be classified into extrinsic muscles, those originating on the anterior or posterior aspect of the lower leg, and intrinsic muscles, originating on the dorsal (top) or plantar (base) aspects of the foot. Extrinsic
All muscles originating on the lower leg except the popliteus muscle are attached to the bones of the foot. The tibia and fibula and the interosseous membrane separate these muscles into anterior and posterior groups, in their turn subdivided into subgroups and layers. Anterior group
Extensor group: the tibialis anterior originates on the proximal half of the tibia and the interosseous membrane and is inserted near the tarsometatarsal joint of the first digit. In the non-weight-bearing leg, the tibialis anterior dorsiflexes the foot and lift its medial edge (supination).
Due to the low tolerance and completion rate of nifurtimox, benznidazole is now being more considered for those who have Chagas disease and require long-term treatment.In the United States nifurtimox is indicated in children and adolescents (birth to less than 18 years of age and weighing at least 2.5 kilograms (5.5 lb) for the treatment of Chagas disease (American Trypanosomiasis), caused by Trypanosoma cruzi.Nifurtimox has also been used to treat African trypanosomiasis (sleeping sickness), and is active in the second stage of the disease (central nervous system involvement). When nifurtimox is given on its own, about half of all patients will relapse, but the combination of melarsoprol with nifurtimox appears to be efficacious. Trials are awaited comparing melarsoprol/nifurtimox against melarsoprol alone for African sleeping sickness.Combination therapy with eflornithine and nifurtimox is safer and easier than treatment with eflornithine alone, and appears to be equally or more effective. It has been recommended as first-line treatment for second-stage African trypanosomiasis. Pregnancy and breastfeeding
Use of nifurtimox should be avoided in pregnant women due to limited use. There is limited data shown that nifurtimox doses up to 15 mg/kg daily can cause adverse effects in breastfed infants. Other authors do not consider breastfeeding a contraindication during nifurtimox use. Side effects
Side effects occur following chronic administration, particularly in elderly people. Major toxicities include immediate hypersensitivity such as anaphylaxis and delayed hypersensitivity reaction involving icterus and dermatitis.