Drug Interaction Report

MONITOR CLOSELY: Lithium may enhance the pharmacologic effects of serotonin reuptake inhibitors (e.g., SSRIs, SNRIs, nefazodone, trazodone) and potentiate the risk of serotonin syndrome, which is a rare but serious and potentially fatal condition thought to result from hyperstimulation of brainstem 5-HT1A and 2A receptors. The exact mechanism by which lithium increases serotonergic activity is unknown. The interaction has been reported with selective serotonin reuptake inhibitors including fluoxetine and fluvoxamine and the serotonin-norepinephrine reuptake inhibitor venlafaxine. Symptoms of the serotonin syndrome 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, rigidity, and ataxia; and gastrointestinal symptoms such as abdominal cramping, nausea, vomiting, and diarrhea.

MANAGEMENT: Caution is advised if lithium is prescribed in combination with serotonin reuptake inhibitors. Patients should be closely monitored for symptoms of the serotonin syndrome during treatment. Particular caution is advised when increasing the dosages of these agents. The potential risk for serotonin syndrome should be considered even when administering serotonergic agents sequentially, as some agents may demonstrate a prolonged elimination half-life. For example, a 5-week washout period is generally recommended following use of fluoxetine before administering another serotonergic agent. If serotonin syndrome develops or is suspected during the course of therapy, all serotonergic agents should be discontinued immediately and supportive care rendered as necessary. Moderately ill patients may also benefit from the administration of a serotonin antagonist (e.g., cyproheptadine, chlorpromazine). Severe cases should be managed under consultation with a toxicologist and may require sedation, neuromuscular paralysis, intubation, and mechanical ventilation in addition to the other measures.

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MONITOR CLOSELY: Coadministration with nonsteroidal anti-inflammatory drugs (NSAIDs) may increase serum lithium levels and induce toxicity in some patients. The exact mechanism of interaction is unknown, but is thought to involve inhibition of renal prostaglandin synthesis by NSAIDs, resulting in decreased renal blood flow and lithium excretion. There have been numerous published reports of lithium toxicity, including severe cases, following the introduction of various NSAIDs including diclofenac, ibuprofen, indomethacin, ketorolac, mefenamic acid, piroxicam, and COX-2 inhibitors. However, pharmacokinetic studies have been somewhat inconsistent, with no significant effects reported for benoxaprofen and etodolac, and up to a 58% increase in serum lithium levels reported for indomethacin. Both decreased serum concentrations of lithium and no effect have been reported for sulindac and aspirin. The interaction is apparently subject to marked interpatient variability.

MANAGEMENT: Given the narrow therapeutic index of lithium, caution is advised during coadministration with NSAIDs, particularly in the elderly or patients with other risk factors (e.g., sodium restriction; renal impairment; congestive heart failure; dehydration; concomitant use of diuretics, ACE inhibitors, or angiotensin II receptor antagonists). Patients should have serum lithium levels checked every 4 to 5 days after starting an NSAID until the extent of any potential interaction can be evaluated. A reduction in lithium dosage may be needed in some cases. Renal function should also be monitored regularly. Patients should be advised to seek medical attention if they experience potential signs and symptoms of lithium toxicity such as drowsiness, dizziness, confusion, muscle weakness, vomiting, diarrhea, polydipsia, polyuria, tinnitus, tremor, ataxia, and blurred vision.

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GENERALLY AVOID: One case series has suggested that benzodiazepines may amplify the teratogenic effects of valproate in the offspring of epileptic women. Both drugs individually have been associated with adverse effects to the fetus. Another study has suggested that valproate may displace diazepam from plasma protein binding sites and inhibit its metabolism; however, the clinical significance has not been established. Other benzodiazepines may interact with valproate in a similar fashion.

MANAGEMENT: Both valproate and benzodiazepines should be avoided during pregnancy unless the potential benefits outweigh the risks to the fetus. In other patients, close observation for clinical evidence of benzodiazepine toxicity (excessive sedation) is recommended if valproate and a benzodiazepine must be used together.

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MONITOR: Central nervous system- and/or respiratory-depressant effects may be additively or synergistically increased in patients taking multiple drugs that cause these effects, especially in elderly or debilitated patients. Sedation and impairment of attention, judgment, thinking, and psychomotor skills may increase.

MANAGEMENT: During concomitant use of these drugs, patients should be monitored for potentially excessive or prolonged CNS and respiratory depression. Cautious dosage titration may be required, particularly at treatment initiation. Ambulatory patients should be counseled to avoid hazardous activities requiring mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

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MONITOR: Central nervous system- and/or respiratory-depressant effects may be additively or synergistically increased in patients taking multiple drugs that cause these effects, especially in elderly or debilitated patients. Sedation and impairment of attention, judgment, thinking, and psychomotor skills may increase.

MANAGEMENT: During concomitant use of these drugs, patients should be monitored for potentially excessive or prolonged CNS and respiratory depression. Cautious dosage titration may be required, particularly at treatment initiation. Ambulatory patients should be counseled to avoid hazardous activities requiring mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

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MONITOR: Central nervous system- and/or respiratory-depressant effects may be additively or synergistically increased in patients taking multiple drugs that cause these effects, especially in elderly or debilitated patients. Sedation and impairment of attention, judgment, thinking, and psychomotor skills may increase.

MANAGEMENT: During concomitant use of these drugs, patients should be monitored for potentially excessive or prolonged CNS and respiratory depression. Cautious dosage titration may be required, particularly at treatment initiation. Ambulatory patients should be counseled to avoid hazardous activities requiring mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

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MONITOR: Central nervous system- and/or respiratory-depressant effects may be additively or synergistically increased in patients taking multiple drugs that cause these effects, especially in elderly or debilitated patients. Sedation and impairment of attention, judgment, thinking, and psychomotor skills may increase.

MANAGEMENT: During concomitant use of these drugs, patients should be monitored for potentially excessive or prolonged CNS and respiratory depression. Cautious dosage titration may be required, particularly at treatment initiation. Ambulatory patients should be counseled to avoid hazardous activities requiring mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

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MONITOR: Central nervous system- and/or respiratory-depressant effects may be additively or synergistically increased in patients taking multiple drugs that cause these effects, especially in elderly or debilitated patients. Sedation and impairment of attention, judgment, thinking, and psychomotor skills may increase.

MANAGEMENT: During concomitant use of these drugs, patients should be monitored for potentially excessive or prolonged CNS and respiratory depression. Cautious dosage titration may be required, particularly at treatment initiation. Ambulatory patients should be counseled to avoid hazardous activities requiring mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

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MONITOR: The efficacy of anticonvulsants may be diminished during coadministration with selective serotonin reuptake inhibitors (SSRIs) or serotonin-norepinephrine reuptake inhibitor (SNRIs). Antidepressants including SSRIs and SNRIs can reduce seizure threshold. In clinical trials, convulsions have typically been reported in 0.1% to 0.3% of patients receiving SSRIs for major depressive disorders. There have been rare reports of prolonged seizures in patients on fluoxetine receiving electroconvulsive therapy (ECT).

MONITOR: Coadministration of SSRIs or SNRIs may potentiate the central nervous system (CNS) adverse effects of anticonvulsants such as somnolence and cognitive and psychomotor impairment.

MONITOR: Coadministration of SSRIs or SNRIs with some anticonvulsants, particularly carbamazepine, eslicarbazepine, oxcarbazepine and valproic acid, may increase the risk of hyponatremia. Treatment with SSRIs or SNRIs has been associated with hyponatremia, which may be due to the syndrome of inappropriate antidiuretic hormone secretion (SIADH) in many cases. While generally reversible following discontinuation of SSRI/SNRI treatment, cases with serum sodium lower than 110 mmol/L have been reported. Hyponatremia and SIADH may also result from treatment with some anticonvulsants. The risk appears to be dose-related, and elderly patients and patients who are volume depleted (e.g., diuretic use) may be at greater risk.

MANAGEMENT: SSRIs and SNRIs should be avoided in patients with unstable epilepsy, and used cautiously in patients with epilepsy controlled with anticonvulsant medications. Treatment with SSRIs and SNRIs should be discontinued if seizures develop or seizure frequency increases. Patients receiving SSRIs or SNRIs with anticonvulsants, particularly carbamazepine, eslicarbazepine, oxcarbazepine and/or valproic acid, should also have serum sodium levels measured regularly and monitored for development of hyponatremia, particularly when higher dosages of these medications are used. Signs and symptoms of hyponatremia include nausea, vomiting, headache, difficulty concentrating, memory impairment, confusion, malaise, lethargy, muscle weakness or spasms, and unsteadiness. In more severe and/or acute cases, hallucination, syncope, seizure, coma, respiratory arrest, and death may occur. Discontinuation of SSRIs and SNRIs should be considered in patients who develop symptomatic hyponatremia, and appropriate medical intervention instituted. All patients receiving concomitant therapy with SSRIs or SNRIs and anticonvulsants should be counseled against driving, operating machinery, or engaging in potentially hazardous activities requiring mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

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MONITOR: Central nervous system- and/or respiratory-depressant effects may be additively or synergistically increased in patients taking multiple drugs that cause these effects, especially in elderly or debilitated patients. Sedation and impairment of attention, judgment, thinking, and psychomotor skills may increase.

MANAGEMENT: During concomitant use of these drugs, patients should be monitored for potentially excessive or prolonged CNS and respiratory depression. Cautious dosage titration may be required, particularly at treatment initiation. Ambulatory patients should be counseled to avoid hazardous activities requiring mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

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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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Animal studies have suggested that oxazepam may inhibit the metabolism of acetaminophen. The clinical implications of this interaction for humans is unknown.

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Hypothermia has been reported in one patient receiving both diazepam and lithium. On rechallenge, the hypothermia was reproducible for the combination, but not for the drugs individually. It is not known whether other benzodiazepines will have similar interactions with lithium.

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GENERALLY AVOID: Chronic, excessive consumption of alcohol may increase the risk of acetaminophen-induced hepatotoxicity, which has included rare cases of fatal hepatitis and frank hepatic failure requiring liver transplantation. The proposed mechanism is induction of hepatic microsomal enzymes during chronic alcohol use, which may result in accelerated metabolism of acetaminophen and increased production of potentially hepatotoxic metabolites.

MANAGEMENT: In general, chronic alcoholics should avoid regular or excessive use of acetaminophen. Alternative analgesic/antipyretic therapy may be appropriate in patients who consume three or more alcoholic drinks per day. However, if acetaminophen is used, these patients should be cautioned not to exceed the recommended dosage (maximum 4 g/day in adults and children 12 years of age or older).

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GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

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GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

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GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

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GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of zolpidem. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

ADJUST DOSING INTERVAL: Administration of zolpidem with food may delay the onset of hypnotic effects. In 30 healthy subjects, administration of zolpidem 20 minutes after a meal resulted in decreased mean peak plasma drug concentration (Cmax) and area under the concentration-time curve (AUC) by 25% and 15%, respectively, compared to fasting. The time to reach peak plasma drug concentration (Tmax) was prolonged by 60%, from 1.4 to 2.2 hours.

MANAGEMENT: Patients receiving zolpidem should be advised to avoid the consumption of alcohol. For faster sleep onset, zolpidem should not be administered with or immediately after a meal.

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GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

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MONITOR: One study has suggested that caffeine withdrawal may significantly increase blood lithium levels. The mechanism may be involve reversal of a caffeine-induced increase in renal lithium excretion.

MANAGEMENT: When caffeine is eliminated from the diet of lithium-treated patients, caution should be exercised. When caffeine consumption is decreased, close observation for evidence of lithium toxicity and worsening of the psychiatric disorder is recommended. Patients should be advised to notify their physician if they experience symptoms of possible lithium toxicity such as drowsiness, dizziness, weakness, ataxia, tremor, vomiting, diarrhea, thirst, blurry vision, tinnitus, or increased urination.

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The recommended maximum number of medicines in the 'Central Nervous System (CNS) Drugs' category to be taken concurrently is usually three. Your list includes four medicines belonging to the 'Central Nervous System (CNS) Drugs' category:

• oxazepam
• Ambien (zolpidem)
• Effexor (venlafaxine)
• Valproate Sodium (valproic acid)

Note: In certain circumstances, the benefits of taking this combination of drugs may outweigh any risks. Always consult your healthcare provider before making changes to your medications or dosage.