Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.
Breathing conditions: If you have asthma and certain other breathing problems, you should not, in general, take beta-blockers such as atenolol. Low doses of atenolol may be taken by people with asthma who do not respond to, or cannot tolerate, alternative treatment but they should be monitored by their doctor.
Cholesterol levels: Increases in cholesterol and triglyceride levels may occur when taking chlorthalidone. Talk to your doctor about whether you need to have your cholesterol levels tested.
Diabetes: Chlorthalidone may make it more difficult for people with diabetes to control their blood sugar. The signs of low blood sugar may not be as noticeable when taking atenolol. Dose adjustment of diabetes medications, including insulin, may be required. If you have diabetes and take insulin or other medications that work by affecting the sugar in the blood, you should monitor your blood sugar carefully while taking this medication.
Drowsiness/reduced alertness: Dizziness or fatigue may occur when starting treatment with this medication. This may impair your ability to drive or operate machinery. Exercise caution with these activities until you find out whether the medication affects you in this way.
Fluid and electrolyte balance: The levels of electrolytes such as potassium, sodium, magnesium, and chloride can be reduced by the use of chlorthalidone. The doctor will periodically check to see whether these are in balance. A potassium supplement may be necessary when taking this medication.
Gout: High levels of uric acid may occur in the blood or gout may be brought on in certain people receiving chlorthalidone.
History of heart failure: If you have a history of heart failure, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.
Hyperthyroidism (high level of thyroid hormones): People with hyperthyroidism should be monitored by their doctor while taking this medication as it may reduce the symptoms of this condition giving a false impression of improvement.
Kidney disease: People with kidney disease should be monitored by their doctor while taking this medication as they are at increased risk of experiencing side effects.
Liver function: People with reduced liver function or progressive liver disease should be monitored by their doctor while taking this medication.
Prinzmetal's angina: Atenolol may increase the number and duration of angina attacks in people with Prinzmetal's angina. If you have this condition, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.
Severe allergies: If you have allergies severe enough to cause anaphylaxis (a severe allergic reaction where swelling of the face, lips, and throat make it difficult to breathe), discuss with your doctor about what to do if you have an allergic reaction. Atenolol may make it more difficult to treat your allergic reaction with epinephrine.
Stopping usage: Atenolol should not be stopped suddenly if you have angina. There have been reports of severe worsening of angina and of heart attack or abnormal heart rhythms occurring in people with angina pectoris who have done this.
Surgery: If you are scheduled for surgery, inform all doctors involved in your care that you are taking a medication that contains atenolol.
Systemic lupus erythematosus: People with systemic lupus erythematosus should be monitored by their doctor while taking chlorthalidone as it may worsen this condition.
Pregnancy: This medication should not be used during pregnancy. If you become pregnant while taking this medication, contact your doctor immediately.
Breast-feeding: Atenolol and chlorthalidone both pass into breast milk. Women who take this medication should not breast-feed.
Children: The safety and effectiveness of using this medication have not been established for children. It is not recommended for use by children.