Drug Interactions between Cymbalta and Painaid

MONITOR: The combined use of low-dose or high-dose aspirin with other nonsteroidal anti-inflammatory drugs (NSAIDs) may increase the potential for serious gastrointestinal (GI) toxicity, including inflammation, bleeding, ulceration, and perforation. Aspirin at anti-inflammatory dosages or higher may also decrease the plasma concentrations of many NSAIDs. The decreases have ranged from none or small (piroxicam, meloxicam, naproxen, tolmetin) to substantial (flurbiprofen, ibuprofen). However, the therapeutic response does not appear to be affected. Investigators theorize that aspirin may displace NSAIDs from plasma protein binding sites, resulting in increased concentration of unbound, or free, drug available for clearance. The increase in NSAID free fraction, and possibly some contributory anti-inflammatory effect from aspirin, may account for the lack of overall effect on therapeutic response.

MANAGEMENT: Caution is advised if aspirin, particularly at anti-inflammatory dosages, is used with other NSAIDs. Concomitant administration of NSAIDs is considered contraindicated or not recommended with aspirin at analgesic/anti-inflammatory dosages by many NSAID manufacturers. 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 abdominal pain, bloating, sudden dizziness or lightheadedness, nausea, vomiting, hematemesis, anorexia, and melena.

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MONITOR: Serotonin reuptake inhibitors (SRIs) may potentiate the risk of bleeding in patients treated with ulcerogenic agents and agents that affect hemostasis such as anticoagulants, platelet inhibitors, thrombin inhibitors, thrombolytic agents, or agents that commonly cause thrombocytopenia. The tricyclic antidepressant, clomipramine, is also a strong SRI and may interact similarly. Serotonin release by platelets plays an important role in hemostasis, thus SRIs may alter platelet function and induce bleeding. Published case reports have documented the occurrence of bleeding episodes in patients treated with psychotropic agents that interfere with serotonin reuptake. Bleeding events related to SRIs have ranged from ecchymosis, hematoma, epistaxis, and petechiae to life-threatening hemorrhages. Additional epidemiological studies have confirmed the association between use of these agents and the occurrence of upper gastrointestinal bleeding, and concurrent use of NSAIDs or aspirin was found to potentiate the risk. Preliminary data also suggest that there may be a pharmacodynamic interaction between SSRIs and oral anticoagulants that can cause an increased bleeding diathesis. Concomitant administration of paroxetine and warfarin, specifically, has been associated with an increased frequency of bleeding without apparent changes in the disposition of either drug or changes in the prothrombin time. Bleeding has also been reported with fluoxetine and warfarin, while citalopram and sertraline have been reported to prolong the prothrombin time of patients taking warfarin by about 5% to 8%. In the RE-LY study (Randomized Evaluation of Long-term anticoagulant therapy), SRIs were associated with an increased risk of bleeding in all treatment groups.

MANAGEMENT: Caution is advised if SRIs or clomipramine are used in combination with other drugs that affect hemostasis. Close clinical and laboratory observation for hematologic complications is recommended. Patients should be advised to promptly report any signs of bleeding to their physician, including pain, swelling, headache, dizziness, weakness, prolonged bleeding from cuts, increased menstrual flow, vaginal bleeding, nosebleeds, bleeding of gums from brushing, unusual bleeding or bruising, red or brown urine, or red or black stools.

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MONITOR: Coadministration with inhibitors of CYP450 1A2 may increase the plasma concentrations of duloxetine, which is a substrate of the isoenzyme. In 14 male study subjects, coadministration with 100 mg fluvoxamine, a potent CYP450 1A2 inhibitor, resulted in a 2.5-fold increase in duloxetine peak plasma concentration (Cmax), a nearly 6-fold increase in duloxetine systemic exposure (AUC), and an approximately 3-fold increase in duloxetine half-life. The interaction has not been studied with less potent CYP450 1A2 inhibitors such as mexiletine, propafenone, and zileuton. Theoretically, high plasma levels of duloxetine may increase the risk of serious adverse effects such as hypertension, hypertensive crisis, increased heart rate, orthostatic hypotension, syncope, and serotonin syndrome. Serotonin syndrome is a rare but serious and potentially fatal condition thought to result from hyperstimulation of brainstem 5-HT1A and 2A receptors. Symptoms may include mental status changes such as irritability, altered consciousness, confusion, hallucinations, and coma; autonomic dysfunction such as tachycardia, hyperthermia, diaphoresis, shivering, blood pressure lability, and mydriasis; neuromuscular abnormalities such as hyperreflexia, myoclonus, tremor, and ataxia; and gastrointestinal symptoms such as abdominal cramping, nausea, vomiting, and diarrhea.

MANAGEMENT: Caution is advised if duloxetine is used in combination with CYP450 1A2 inhibitors. Pharmacologic response to duloxetine should be monitored more closely whenever a CYP450 1A2 inhibitor is added to or withdrawn from therapy, and the dosage adjusted as necessary.

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MONITOR: Serotonin reuptake inhibitors (SRIs) may potentiate the risk of bleeding in patients treated with ulcerogenic agents and agents that affect hemostasis such as anticoagulants, platelet inhibitors, thrombin inhibitors, thrombolytic agents, or agents that commonly cause thrombocytopenia. The tricyclic antidepressant, clomipramine, is also a strong SRI and may interact similarly. Serotonin release by platelets plays an important role in hemostasis, thus SRIs may alter platelet function and induce bleeding. Published case reports have documented the occurrence of bleeding episodes in patients treated with psychotropic agents that interfere with serotonin reuptake. Bleeding events related to SRIs have ranged from ecchymosis, hematoma, epistaxis, and petechiae to life-threatening hemorrhages. Additional epidemiological studies have confirmed the association between use of these agents and the occurrence of upper gastrointestinal bleeding, and concurrent use of NSAIDs or aspirin was found to potentiate the risk. Preliminary data also suggest that there may be a pharmacodynamic interaction between SSRIs and oral anticoagulants that can cause an increased bleeding diathesis. Concomitant administration of paroxetine and warfarin, specifically, has been associated with an increased frequency of bleeding without apparent changes in the disposition of either drug or changes in the prothrombin time. Bleeding has also been reported with fluoxetine and warfarin, while citalopram and sertraline have been reported to prolong the prothrombin time of patients taking warfarin by about 5% to 8%. In the RE-LY study (Randomized Evaluation of Long-term anticoagulant therapy), SRIs were associated with an increased risk of bleeding in all treatment groups.

MANAGEMENT: Caution is advised if SRIs or clomipramine are used in combination with other drugs that affect hemostasis. Close clinical and laboratory observation for hematologic complications is recommended. Patients should be advised to promptly report any signs of bleeding to their physician, including pain, swelling, headache, dizziness, weakness, prolonged bleeding from cuts, increased menstrual flow, vaginal bleeding, nosebleeds, bleeding of gums from brushing, unusual bleeding or bruising, red or brown urine, or red or black stools.

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One study has reported that coadministration of caffeine and aspirin lead to a 25% increase in the rate of appearance and 17% increase in maximum concentration of salicylate in the plasma. A significantly higher area under the plasma concentration time curve of salicylate was also reported when both drugs were administered together. The exact mechanism of this interaction has not been specified. Physicians and patients should be aware that coadministration of aspirin and caffeine may lead to higher salicylate levels faster.

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