Synthroid is the brand name for the drug levothyroxine and is prescribed to treat hypothyroidism. MedlinePlus, an online medical encyclopedia provided by the U.S. National Library of Medicine, reports that hypothyroidism is a disorder where the thyroid does not produce enough of the hormone thyroxine. The symptoms of hypothyroidism are, according to MedlinePlus: weight gain, loss of hair, skin that is thick and dry and increased sensitivity to cold temperatures. Generic Synthroid can reverse these symptoms but may cause certain side effects.
Gastrointenstinal Effects
MedlinePlus reports that generic Synthroid may cause certain gastrointestinal side effects. These side effects include nausea, vomiting, diarrhea, stomach cramps and increased appetite. Despite the increased appetite, generic Synthroid may actually cause unintentional weight loss.
Temperature Sensitivity
While one of the symptoms of hypothyroidism is excessive sensitivity to cold temperatures, MedlinPlus reports that generic Synthroid may cause the opposite side effect--increased sensitivity to the heat. Synthroid may also cause excessive sweating.
Effects on Breathing and Heart Beat
Synthroid may also cause changes changes in lung and cardiovascular function, though these side effects, according to the Mayo Clinic, are less common. For example, generic Synthoid may cause breathing to become difficult or irregular and may cause wheezing. Generic Synthroid also has the potential to cause changes in the way the heart beats. The heart rate may feel excessively fast or slow or may feel irregular. The heart beat may feel very strong, like it is pounding in the chest, and the blood pressure may increase. In severe cases, the heart may even stop beating. The Mayo Clinic also notes that generic Synthroid may cause the veins in the neck to become bigger. Because of these changes in breathing and heartbeat may reduce the amount of oxygen that reaches the brain, dizziness or fainting may occur. If any of these side effects are experienced, the Mayo Clinic advises seeking immediate medical attention.
Other Side Effects
Generic Synthroid may cause multiple varied but rare side effects. Drugs.com reports that generic Synthroid may cause joint pain and cramping of the muscles in the legs. If the person taking generic Syntrhoid is allergic to the drug, he may have an allergic reaction. Symptoms of an allergic reaction include a rash or hives, itching, flushing, tightness in the chest, a hoarse voice and swelling in the mouth, tongue, lips or face. Drugs.com also reports that generic Synthroid may cause changes in mood, anxiety, nervousness and irritability.
