Drug Interactions between fosinopril / hydrochlorothiazide and levomilnacipran

MONITOR: Although they are frequently combined in clinical practice, diuretics and angiotensin converting enzyme (ACE) inhibitors may have additive effects. Coadministration makes hypotension and hypovolemia more likely than does either drug alone. Some ACE inhibitors may attenuate the increase in the urinary excretion of sodium caused by some loop diuretics. Some patients on diuretics, especially those on dialysis or a dietary salt restriction, may experience acute hypotension with lightheadedness and dizziness after receiving the first dose of the ACE inhibitor. In addition, ACE inhibitors may cause renal insufficiency or acute renal failure in patients with sodium depletion or renal artery stenosis.

MANAGEMENT: Monitoring of blood pressure, diuresis, electrolytes, and renal function is recommended during coadministration. The possibility of first-dose hypotensive effects may be minimized by initiating therapy with small doses of the ACE inhibitor, or either discontinuing the diuretic temporarily or increasing the salt intake approximately one week prior to initiating an ACE inhibitor. Alternatively, the patient may remain under medical supervision for at least two hours after the first dose of the ACE inhibitor, or until blood pressure has stabilized.

MONITOR: Coadministration with diuretics may potentiate the risk of hyponatremia associated with the use of selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs). The mechanism by which SSRIs and SNRIs produce hyponatremia has not been clearly established. In many cases, the hyponatremia appears to be secondary to the syndrome of inappropriate antidiuretic hormone secretion (SIADH). Cases with serum sodium lower than 110 mmol/L have been reported. These events are generally reversible following discontinuation of therapy and/or medical intervention. Elderly patients and patients taking diuretics or who are otherwise volume-depleted may be at greater risk of developing hyponatremia with SSRIs and SNRIs.

MONITOR: Antihypertensive agents such as diuretics may potentiate the orthostatic effect that is occasionally observed upon the initiation of SSRI or SNRI therapy. Syncope and orthostatic hypotension tend to occur within the first week of SNRI/SSRI therapy but can occur at any time during treatment, particularly after a dosage increase. The use of SSRIs or SNRIs may also cause sustained increases in blood pressure and heart rate, which may antagonize the therapeutic effects of antihypertensive medications. Cases of elevated blood pressure requiring immediate treatment have been reported in postmarketing experience.

MANAGEMENT: Caution is recommended if SSRIs or SNRIs are prescribed in combination with diuretics, particularly in the elderly. Patients should be advised to seek medical attention if they experience potential signs and symptoms of hyponatremia such as nausea, vomiting, headache, malaise, lethargy, irritability, difficulty concentrating, memory impairment, confusion, weakness, muscle spasm, and unsteadiness (which may lead to falls). More severe and/or acute cases may include hallucination, syncope, seizure, coma, respiratory arrest, and death. Discontinuation of SSRI/SNRI therapy should be considered in patients who develop symptomatic hyponatremia, and appropriate medical intervention instituted as necessary. Patients should also have their blood pressure and pulse monitored before and during SSRI/SNRI therapy, especially during the first few weeks and following a dosage increase. Patients should be advised to avoid rising abruptly from a sitting or recumbent position and to notify their doctor if they experience dizziness, lightheadedness, syncope, orthostasis, or tachycardia. Patients should also avoid driving or operating hazardous machinery until they know how the medications affect them. Dose reduction or drug discontinuation should be considered in patients who experience a sustained increase in blood pressure or pulse rate during SSRI or SNRI therapy.