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Drug Interactions between macitentan / tadalafil and sodium nitrite

This report displays the potential drug interactions for the following 2 drugs:

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Interactions between your drugs

Major

sodium nitrite tadalafil

Applies to: sodium nitrite and macitentan / tadalafil

When use of sodium nitrite is required, the doctor should be told if you have been receiving treatment with tadalafil. Sodium nitrite can cause hypotension (low blood pressure), and the risk may be greater when combined with other medications that decrease blood pressure such as tadalafil. Excessively low blood pressure can lead to shock, collapse, coma, or even death. Your doctor will need to monitor you closely and possibly take extra precautions for you to safely use these medications together. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Major

sodium nitrite macitentan

Applies to: sodium nitrite and macitentan / tadalafil

Consumer information for this interaction is not currently available.

MONITOR CLOSELY: Coadministration with antihypertensive agents, diuretics, vasodilators, or phosphodiesterase-5 (PDE5) inhibitors may potentiate the hypotensive effect of sodium nitrite. Since sodium nitrite can cause serious hypotension and methemoglobin formation, patients may be at increased risk for complications related to inadequate perfusion and oxygenation. In healthy volunteers, oral doses of 120 to 180 mg caused minimal cardiovascular changes when subjects were maintained in the horizontal position. However, subjects exhibited tachycardia and hypotension with syncope within minutes after being placed in the upright position. A wide range of methemoglobin concentrations may occur following sodium nitrite administration. Methemoglobin concentrations as high as 58% have been reported after administration of two 300 mg doses to an adult. There have been reports of severe hypotension, methemoglobinemia, cardiac dysrhythmias, coma, and death in patients without life-threatening cyanide poisoning but who were treated with injection of sodium nitrite at dosages less than twice those recommended for the treatment of cyanide poisoning.

MANAGEMENT: Sodium nitrite should be used with caution and close monitoring in the presence of concomitant antihypertensive agents, diuretics, vasodilators, or PDE5 inhibitors. Hemodynamics should be monitored during and after administration of sodium nitrite, and the infusion rate decreased if significant hypotension occurs. In addition, methemoglobin levels should be monitored and oxygen administered during treatment whenever possible.

Minor

tadalafil macitentan

Applies to: macitentan / tadalafil and macitentan / tadalafil

Information for this minor interaction is available on the professional version.

Drug and food/lifestyle interactions

Moderate

tadalafil food/lifestyle

Applies to: macitentan / tadalafil

Tadalafil can lower blood pressure, and combining it with alcohol may further increase this effect. You may be more likely to experience symptoms such as dizziness, lightheadedness, fainting, flushing, headache, and heart palpitations. You should avoid or limit the use of alcohol to not more than 4 alcohol-containing drinks during a small period of time while being treated with tadalafil, and use caution when getting up from a sitting or lying position. You may also want to avoid drinking large amounts of grapefruit juice, since it may increase the blood levels and effects of tadalafil. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Moderate

macitentan food/lifestyle

Applies to: macitentan / tadalafil

Consumer information for this interaction is not currently available.

GENERALLY AVOID: Coadministration with grapefruit juice may increase the plasma concentrations of macitentan, which is primarily metabolized by CYP450 3A4. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. The interaction has not been studied with grapefruit juice but has been reported for ketoconazole, a potent CYP450 3A4 inhibitor. In ten healthy subjects, coadministration of a single 10 mg oral dose of macitentan on day 5 of treatment with ketoconazole (400 mg daily for 24 days) resulted in an approximately 2-fold increase in macitentan systemic exposure compared to administration alone. However, the clinical significance of the interaction is unclear. In general, the effect of grapefruit juice is concentration-, dose- and preparation-dependent, and can vary widely among brands. Certain preparations of grapefruit juice (e.g., high dose, double strength) have sometimes demonstrated potent inhibition of CYP450 3A4, while other preparations (e.g., low dose, single strength) have typically demonstrated moderate inhibition. Pharmacokinetic interactions involving grapefruit juice are also subject to a high degree of interpatient variability, thus the extent to which a given patient may be affected is difficult to predict.

MANAGEMENT: Until further information is available, patients receiving macitentan therapy should avoid the consumption of grapefruit or grapefruit juice.

Therapeutic duplication warnings

No warnings were found for your selected drugs.

Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.

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Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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