Drug Interactions between dexamethasone / ketorolac / moxifloxacin and plazomicin

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: 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.

MONITOR: The nephrotoxic effect of aminoglycosides may be potentiated by nonsteroidal anti-inflammatory drugs (NSAIDs), particularly if the latter had been given in high dosages for prolonged periods. Four children with cystic fibrosis who had been receiving chronic ibuprofen developed acute renal insufficiency shortly after initiation of IV aminoglycoside therapy for pulmonary exacerbations. An adolescent with CF who received intermittent, standard-dose ibuprofen during treatment with IV gentamicin also developed renal failure in addition to severe vestibular toxicity. Animal models suggest that renal prostaglandins may play a role in maintaining normal renal blood flow and glomerular filtration rate during the development of aminoglycoside nephrotoxicity, thus inhibition of their production by NSAIDs may worsen the renal damage.

MANAGEMENT: Whenever feasible, NSAID use should preferably be discontinued prior to initiating IV aminoglycoside therapy. If concomitant administration is necessary, hydration status as well as renal and vestibular functions should be closely monitored.

MONITOR: In premature infants, NSAIDs may increase the plasma concentrations of aminoglycosides. The proposed mechanism is decreased aminoglycoside clearance due to NSAID reduction of glomerular filtration rate, which is already low in premature infants. In a study of 20 preterm infants who had been given at least three days of amikacin or gentamicin therapy, mean peak plasma concentration increased by 17% and 33%, and mean trough concentration increased by 29% and 48%, respectively, on day 1 following administration of IV indomethacin for patent ductus arteriosus. Serum creatinine increased by 17%, while urine output and serum sodium decreased. Six patients developed hyponatremia.

MANAGEMENT: It may be advisable to consider reducing the dosage of aminoglycoside prior to initiation of NSAID therapy in infants. During coadministration, plasma antibiotic concentrations and renal function should be closely monitored, and the antibiotic dosage further adjusted as necessary.