Following oral administration, peak plasma concentrations are reached within 50-75 minutes. Caffeine is distributed rapidly to all body tissues and readily crosses the blood-brain and placental barriers. It is distributed into breast milk. The drug is partially metabolized in the liver, and unchanged drug and metabolites are excreted in the urine. Caffeine should not be consumed by patients suffering from insomnia, nor should it be consumed prior to retiring because it can cause insomnia.
Caffeine is relatively contraindicated in patients with cardiac disease.
Caffeine can stimulate the force of contraction and can increase heart rate. Patients who have angina or a history of cardiac arrhythmias should not receive or should minimize their intake of caffeine. Caffeine should be used cautiously in patients with hepatic disease or hepatic impairment. Caffeine clearance may be delayed, leading to toxicity. Patients with hypertension should not receive or should minimize their intake of caffeine.