Complications of the kissing disease might be more serious than the condition itself. Mono may lead to enlargement of the spleen. In the worst case, the organ might rupture causing sharp pain in the left side of the upper abdomen. The affected person needs medical care immediately, and probably even surgery.
Other complications could include liver problems, e.g. hepatitis and jaundice, and at times, anemia, heart problems, swollen tonsils (which can result in breathing problems) as well as thrombocytopenia, meningitis, encephalitis, etc.
However, in people with a weakened immune system and in patients who must take drugs to suppress immunity after an organ transplant, the Epstein-Barr virus may lead to a much more serious condition.
Regarding medicaments, there might be a risk of rash with some medications, such as Amoxicillin and other penicillin derivatives. A few people with mono who take one of these drugs might develop a rash. They should rather use other antibiotics that treat infections that sometimes accompany kissing disease.