Diuretic-induced [for example, by furosemide (Lasix)] reduction in blood potassium or magnesium levels may predispose patients to digoxin-induced abnormal heart rhythms.

Saquinavir (Invirase) and ritonavir (Norvir) increase the amount of digoxin in the body and may cause digoxin toxicity.

PREGNANCY: There are no adequate studies in pregnant women.

NURSING MOTHERS: Digoxin in secreted in breast milk at concentrations similar to concentrations in the mothers blood. However, the total amount of digoxin that will be absorbed from breast milk by the infant may not be enough to cause effects. Caution should be exercised by nursing mothers who are taking digoxin.

SIDE EFFECTS: Common side effects include nausea, vomiting, headache, dizziness, skin rash, and mental changes. Many digoxin side effects are dose dependent and happen when blood levels are over the narrow therapeutic range. Therefore, digoxin side effects can be avoided by keeping blood levels within the therapeutic level. Serious side effects associated with digoxin include heart block, rapid heartbeat, and slow heart rate. Digoxin has also been associated with visual disturbance (blurred or yellow vision), abdominal pain, and breast enlargement. Patients with low blood potassium levels can develop digoxin toxicity even when digoxin levels are not considered elevated. Similarly, high calcium and low magnesium blood levels can increase digoxin toxicity and produce serious disturbances in heart rhythm.

Reference: FDA Prescribing Information