Betaloc side effects can slow down the heart rate and cause weakness and cold extremities. However, in some people with an already slow heart rate, taking Betalac may cause continued slowing of the heart rate, as well as side effects that can lower blood pressure and cause bronchospasm and arteriosclerosis occlusion in both lower extremities. The side effects of Betalac on the central nervous system can cause dizziness, headache, vertigo, insomnia, and excessive dreaming. For the digestive system can cause nausea, vomiting, diarrhea, abdominal pain. Therefore, it is important to monitor heart rate when using Betalac. Betalactam may also affect blood sugar and blood lipids. For patients with more serious heart disease with a slowed heart rate, special attention must be paid when taking it, starting with a small dose and gradually increasing the dosage according to the condition, and always take the medication as prescribed by your doctor.