The allergy medicine cyproheptadine does not carry a high risk of known serious side effects. Cyproheptadine side effects that are most common, though, produce a wide variety of medical issues. These range from sleepiness or restlessness to headaches and dry throat, but normally these are not serious and are merely temporary. Potentially serious effects include allergy, mental disturbances and seizures, but these occur only rarely.
Generally cyproheptadine is taken by mouth, either as a tablet or as a liquid. It is an antihistamine, which means that it reduces the effect of high histamine levels in the body, which normally produce inflammation, redness and irritation. Antihistamines in general are useful against medical conditions that involve an overactive immune system, such as hayfever or skin rashes. Although they cannot cure allergies, they can improve the symptoms and make the patient more comfortable.
Gastrointestinal issues are some of the most common cyproheptadine side effects, and include upset stomach and constipation. Patients may also develop a larger appetite, and can put on weight while using the drug. Alertness can also be adversely affected, with consumers developing an unusual sleepiness, and the list of common cyproheptadine side effects can also include a deterioration in coordination or muscle strength and dizziness. Unusual displays of excitement or of nervousness may also be due to the use of the drug.
Cyproheptadine can also affect the mucus production in the airways, which can be beneficial for people suffering from flu-like symptoms as a result of their allergies, but can also be detrimental when it produces undesirable effects. Normally, the interior membranes of the throat, mouth and nose have a protective damp quality and mucus, but one of the cyproheptadine side effects is to dry out these areas. Alternatively, people who take cyproheptadine may find that the mucus in the throat or nose becomes thicker and harder to clear than normal.
Rarer side effects of the drug can be serious enough to require emergency medical attention. These include allergies, which produce symptoms like facial swelling and problems breathing. Effects on the brain can alter the way the person acts or thinks, and can even produce confusion or hallucinations. Liver damage can produce a yellowing of the skin and eyes; if the kidneys are damaged by the drug, the person can experience a darkening of the urine. More possible dangerous side effects include blurring of the vision or severe vomiting, and these all require a doctor's examination.