Drug Interactions between dexamethasone / ketorolac / moxifloxacin and moexipril

MONITOR CLOSELY: Concomitant administration of corticosteroids may potentiate the risk of tendinitis and tendon rupture associated with fluoroquinolone treatment. The mechanism is unknown. Tendinitis and tendon rupture have most frequently involved the Achilles tendon, although cases involving the rotator cuff (the shoulder), the hand, the biceps, and the thumb have also been reported. Some have required surgical repair or resulted in prolonged disability. Tendon rupture can occur during or up to several months after completion of fluoroquinolone therapy.

MANAGEMENT: Caution is recommended if fluoroquinolones are prescribed in combination with corticosteroids, particularly in patients with other concomitant risk factors (e.g., age over 60 years; recipient of kidney, heart, and/or lung transplant). Patients should be advised to stop taking the fluoroquinolone, avoid exercise and use of the affected area, and promptly contact their physician if they experience pain, swelling, or inflammation of a tendon. In general, fluoroquinolones should only be used to treat conditions that are proven or strongly suspected to be caused by bacteria and only if the benefits outweigh the risks.

MONITOR: The combined use of corticosteroids and nonsteroidal anti-inflammatory drugs (NSAIDs) may increase the potential for serious gastrointestinal (GI) toxicity, including inflammation, bleeding, ulceration, and perforation. In a large, case-control study of elderly patients, those who used corticosteroids and NSAIDs concurrently had an estimated relative risk (RR) for peptic ulcer disease and GI hemorrhage of 14.6 compared to those who used neither. Corticosteroid use was associated with a doubling of the risk (estimated RR = 2.0), but the risk was confined to those who also used NSAIDs. It is possible that both categories of agents are ulcerogenic and have additive effects on the GI mucosa during coadministration. Some investigators have also suggested that the primary effect of corticosteroids in this interaction is to delay healing of erosions caused by NSAIDs rather than cause de novo ulcerations.

MANAGEMENT: Caution is advised if corticosteroids and NSAIDs are used together, especially in patients with a prior history of peptic ulcer disease or GI bleeding and in elderly and debilitated patients. During concomitant therapy, patients should be advised to take the medications with food and to immediately report signs and symptoms of GI ulceration and bleeding such as severe abdominal pain, dizziness, lightheadedness, and the appearance of black, tarry stools. The selective use of prophylactic anti-ulcer therapy (e.g., antacids, H2-antagonists) may be considered.

MONITOR: Corticosteroids may antagonize the effects of antihypertensive medications by inducing sodium and fluid retention. These effects may be more common with the natural corticosteroids (cortisone, hydrocortisone) because they have greater mineralocorticoid activity. Conversely, some calcium channel blockers such as diltiazem and verapamil may increase corticosteroid plasma levels and effects by inhibiting their clearance via CYP450 3A4 metabolism.

MANAGEMENT: Patients on prolonged (i.e., longer than about a week) or high-dose corticosteroid therapy should have blood pressure, electrolyte levels, and body weight monitored regularly, and be observed for the development of edema and congestive heart failure. The dosages of antihypertensive medications may require adjustment.

MONITOR: Nonsteroidal anti-inflammatory drugs (NSAIDs) may attenuate the antihypertensive effects of ACE inhibitors. The proposed mechanism is NSAID-induced inhibition of renal prostaglandin synthesis, which results in unopposed pressor activity producing hypertension. In addition, NSAIDs can cause fluid retention, which also affects blood pressure. Some NSAIDs may also alter the pharmacokinetics of certain ACE inhibitors. For example, oxaprozin has been shown to reduce the systemic exposure (AUC) of enalapril and its active metabolite, enalaprilat.

MONITOR: Concomitant use of NSAIDs and ACE inhibitors may cause deterioration in renal function, particularly in patients who are elderly or volume-depleted (including those on diuretic therapy) or have compromised renal function. Acute renal failure may occur, although effects are usually reversible. Chronic use of NSAIDs alone may be associated with renal toxicities, including elevations in serum creatinine and BUN, tubular necrosis, glomerulitis, renal papillary necrosis, acute interstitial nephritis, nephrotic syndrome, and renal failure. Additionally, in patients with prerenal conditions whose renal perfusion may be dependent on the function of prostaglandins, NSAIDs may precipitate overt renal decompensation via a dose-related inhibition of prostaglandin synthesis. ACE inhibitors can further worsen renal function by blocking the effect of angiotensin II-mediated efferent arteriolar vasoconstriction, thereby decreasing glomerular filtration.

MANAGEMENT: Patients receiving ACE inhibitors who require prolonged (greater than 1 week) concomitant therapy with an NSAID should have blood pressure monitored more closely following initiation, discontinuation, or change of dosage of the NSAID. Renal function should also be evaluated periodically during prolonged coadministration. The interaction is not expected to occur with low doses (e.g., low-dose aspirin) or intermittent short-term administration of NSAIDs.

MONITOR: Coadministration with nonsteroidal anti-inflammatory drugs (NSAIDs) may potentiate the risk of central nervous system toxicity sometimes associated with fluoroquinolone use. The interaction has been reported most often with enoxacin. It may occur with other fluoroquinolones as well, but is poorly documented. The exact mechanism of interaction is unknown. Some investigators suggest that the piperazine ring of fluoroquinolones may inhibit the binding of gamma-aminobutyric acid (GABA) to brain receptors and that NSAIDs may synergistically add to this effect. Patients with a history of seizures may be at greater risk.

MANAGEMENT: Clinical monitoring for signs of CNS stimulation such as tremors, involuntary muscle movements, hallucinations, or seizures is recommended if fluoroquinolone antibiotics are prescribed in combination with NSAIDs.