Drug Interactions between Chewable Calcium with Vitamin D and erlotinib

Calcium absorption may be increased by taking it with food. However, foods high in oxalic acid (spinach or rhubarb), or phytic acid (bran and whole grains) may decrease calcium absorption. Calcium may be taken with food to increase absorption. Consider spacing calcium administration for at least 2 hours before or after consuming foods high in oxalic acid or phytic acid. Talk to your doctor if you have any questions or concerns. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Treatment with ergocalciferol may require you to adjust your dietary intake of foods which contain natural or added calcium, phosphate (organic and inorganic), and vitamin D. Ingesting too much vitamin D or having elevated calcium and/or phosphorus levels in the blood and urine can lead to toxic effects, such as having an irregular heart rhythm, seizures, kidney stones, and eventual calcification of your blood vessels, cornea and/or the soft tissues in your body. Your doctor will monitor the levels of calcium and phosphorus in your blood during treatment with ergocalciferol. Please speak with your healthcare team to determine if you require a specialized diet, particularly if you have reduced kidney function, and to discuss any other questions or concerns you have. You may require additional monitoring or a dose adjustment of ergocalciferol if your diet changes. Fortified foods will state on their labeling how much calcium, phosphate, and/or vitamin D has been added. The National Institutes of Health, Office of Dietary Supplements also provides information on which foods contain calcium, phosphorus, and vitamin D. You should avoid abrupt changes in your dietary calcium intake and seek medical attention if you experience early symptoms of vitamin D intoxication such as weakness, fatigue, headache, drowsiness, vertigo, ringing in the ears, loss of appetite, nausea, vomiting, constipation, dry mouth, metallic taste, muscle pain, bone pain, muscle incoordination, and low muscle tone. Late symptoms may include frequent urination, excessive thirst, weight loss, conjunctivitis ("pink eye"), light sensitivity, runny nose, itching, increased body temperature, and irregular heart rhythm. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Erlotinib should be taken on an empty stomach at least 1 hour before or 2 hours after a meal and at the same time each day unless otherwise directed by your doctor. You should also avoid grapefruit and grapefruit juice while taking erlotinib. Food and grapefruit juice can increase the absorption of erlotinib from the gastrointestinal tract, which may lead to higher blood levels of the medication and possibly increased side effects. If you are a smoker, you should try to quit as soon as you can. Cigarette smoking can reduce the blood levels of erlotinib, which may make the medication less effective in treating your cancer. It is best to avoid smoking during erlotinib therapy. Talk to a healthcare professional if you have any questions or concerns. If you start smoking or undergo smoking cessation, your doctor may need to adjust your dose of erlotinib. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.