Drug Interactions between dexamethasone / ketorolac / moxifloxacin and troglitazone

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 troglitazone may decrease the plasma concentrations of drugs that are substrates of the CYP450 3A4 isoenzyme. The mechanism is accelerated clearance due to induction of CYP450 3A4 activity by troglitazone.

MANAGEMENT: Caution is advised if troglitazone must be used concomitantly with medications that undergo metabolism by CYP450 3A4, particularly those with a narrow therapeutic range. Dosage adjustments as well as clinical and laboratory monitoring may be appropriate for some drugs whenever troglitazone is added to or withdrawn from therapy.

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: Quinolone antibiotics may interfere with the therapeutic effects of insulin and other antidiabetic agents. The use of quinolones has been associated with disturbances in blood glucose homeostasis possibly stemming from effects on pancreatic beta cell ATP-sensitive potassium channels that regulate insulin secretion. Both hyperglycemia and hypoglycemia have been reported, usually in diabetic patients receiving concomitant treatment with an oral hypoglycemic agent (e.g., sulfonylurea) or insulin. Although hyperglycemia is significantly more common and infection itself may be an underlying risk factor, hypoglycemia may cause greater morbidity and mortality. An internal safety review conducted by the U.S. Food and Drug Administration (FDA) identified at least 67 reports of severe hypoglycemia associated with quinolone use resulting in coma, death, or permanent and disabling injuries, primarily in elderly and diabetic patients with renal impairment and/or complicated infections. This is in addition to the numerous cases that have been reported for gatifloxacin, which led to its withdrawal from the U.S. market in 2008. Of the five quinolones that the FDA reviewed, levofloxacin had the most cases (44), followed by ciprofloxacin (12), moxifloxacin (9), ofloxacin (2), and gemifloxacin (0). Other quinolones such as nalidixic acid and norfloxacin, as well as some others that have never been marketed or are no longer marketed such as clinafloxacin and temafloxacin, have also been associated with dysglycemia, thus it is generally believed to be a class effect, albeit with varying risks amongst the individual agents. Available data also seem to indicate different time frames for the development of hypo- and hyperglycemia, with the former generally occurring within 1 to 3 days following quinolone initiation and the latter within 4 to 10 days later.

MANAGEMENT: Blood glucose should be closely monitored whenever quinolones are prescribed to diabetic patients, especially if they are elderly, have renal impairment, or are severely ill. Patients should be apprised of the increased risk of dysglycemia and be particularly alert to potential signs and symptoms of hypoglycemia such as headache, dizziness, drowsiness, nervousness, confusion, tremor, hunger, weakness, perspiration, palpitation, and tachycardia. If hypoglycemia occurs, patients should initiate appropriate remedial therapy immediately, discontinue the quinolone, and contact their physician. Alternative antibiotics may need to be considered.