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When blood is deoxygenated and flowing back to the heart through the veins, it is dark reddish-blue in color. Blood in the arteries that is oxygenated and flowing out to the body is bright red. Whereas arterial blood comes out in spurts, venous blood flows.
The strongest synthetic topical retinoid drug available, tazarotene, is used to treat sun-damaged skin, acne, and psoriasis.
It is believed that the Incas used anesthesia. Evidence supports the theory that shamans chewed cocoa leaves and drilled holes into the heads of patients (letting evil spirits escape), spitting into the wounds they made. The mixture of cocaine, saliva, and resin numbed the site enough to allow hours of drilling.
Bisphosphonates were first developed in the nineteenth century. They were first investigated for use in disorders of bone metabolism in the 1960s. They are now used clinically for the treatment of osteoporosis, Paget's disease, bone metastasis, multiple myeloma, and other conditions that feature bone fragility.
Side effects from substance abuse include nausea, dehydration, reduced productivitiy, and dependence. Though these effects usually worsen over time, the constant need for the substance often overcomes rational thinking.

