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Drug Interactions between riociguat and tadalafil

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

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Interactions between your drugs

Major

tadalafil riociguat

Applies to: tadalafil and riociguat

CONTRAINDICATED: Coadministration of riociguat with phosphodiesterase (PDE) inhibitors may cause significant hypotension. The mechanism involves peripheral vasodilation secondary to enhanced levels of cyclic guanosine monophosphate (cGMP) in vascular smooth muscle cells, as PDE inhibitors prevent degradation of cGMP while riociguat promotes its synthesis by stimulating soluble guanylate cyclase (sGC), an enzyme in the cardiopulmonary system that binds with nitric oxide (NO) to catalyze the synthesis of cGMP. In seven study patients with pulmonary arterial hypertension (PAH) on stable sildenafil treatment (20 mg three times a day), coadministration of single doses of riociguat (0.5 mg and 1 mg sequentially) demonstrated additive hemodynamic effects. One death has been reported in clinical studies of PAH patients on stable sildenafil treatment receiving riociguat 1 to 2.5 mg three times a day, and there was a high rate of discontinuation for hypotension. Riociguat does not affect the pharmacokinetics of sildenafil.

MANAGEMENT: Concomitant use of riociguat with PDE inhibitors, including specific PDE-5 inhibitors (e.g., avanafil, sildenafil, tadalafil, vardenafil) or nonspecific PDE inhibitors (e.g., dipyridamole, theophylline), is considered contraindicated. Riociguat should be discontinued at least 24 hours before administering a PDE-5 inhibitor, and avoidance of riociguat administration within 24 hours after sildenafil or within 48 hours after tadalafil is recommended. Limited data exists for other PDE inhibitors.

References

  1. Cerner Multum, Inc. "UK Summary of Product Characteristics."
  2. Cerner Multum, Inc. "Australian Product Information."
  3. (2013) "Product Information. Adempas (riociguat)." Bayer Pharmaceutical Inc

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Drug and food interactions

Moderate

tadalafil food

Applies to: tadalafil

GENERALLY AVOID: Additive hypotensive effects may occur when phosphodiesterase-5 (PDE5) inhibitors such as tadalafil are used with alcohol, as both are mild systemic vasodilators. In clinical pharmacology studies, more subjects administered alcohol at a dose of 0.7 g/kg (equivalent to approximately 6 ounces of 80-proof vodka in an 80-kg male; consumed within 10 minutes in study subjects, providing blood alcohol levels of 0.08%) in combination with tadalafil 10 or 20 mg single doses had clinically significant decreases in blood pressure than with alcohol alone. There were reports of postural dizziness, and orthostatic hypotension was observed in some. When tadalafil 20 mg was administered with alcohol at a lower dose of 0.6 g/kg (equivalent to approximately 4 ounces of 80-proof vodka in an 80-kg male), orthostatic hypotension was not observed, dizziness occurred with similar frequency relative to alcohol alone, and the hypotensive effects of alcohol were not potentiated. Neither tadalafil nor alcohol affected the plasma concentrations of the other.

GENERALLY AVOID: Coadministration with grapefruit juice is likely to increase the plasma concentrations of tadalafil, which is primarily metabolized by CYP450 3A4. However, the interaction has not been studied. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit.

MANAGEMENT: Patients taking tadalafil should avoid consuming large amounts of alcohol (for example, 5 units or more), which may increase the potential for orthostatic signs and symptoms including increase in heart rate, decrease in standing blood pressure, dizziness, and headache. It may also be appropriate to avoid consuming large amounts of grapefruit juice.

References

  1. (2003) "Product Information. Cialis (tadalafil)." Lilly, Eli and Company
  2. (2009) "Product Information. Adcirca (tadalafil)." United Therapeutics Corporation

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Moderate

riociguat food

Applies to: riociguat

ADJUST DOSE: Smoking may decrease the plasma concentrations of riociguat. The proposed mechanism is induction of the CYP450 1A1-mediated metabolism of riociguat by polycyclic aromatic hydrocarbons present in cigarette smoke. CYP450 1A1 is responsible for the formation of the major active metabolite, M1, which has just 1/3 to 1/10 the pharmacologic activity of riociguat. According to the product labeling, plasma concentrations of riociguat are reduced by 50% to 60% in smokers compared to nonsmokers.

MANAGEMENT: Riociguat dosages higher than 2.5 mg three times a day may be considered in cigarette smokers, if tolerated, so as to match the exposure seen in nonsmoking patients. However, safety and effectiveness of higher dosages have not been established. A dosage reduction should be considered in patients who stop smoking during treatment with riociguat.

References

  1. (2013) "Product Information. Adempas (riociguat)." Bayer Pharmaceutical Inc

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Therapeutic duplication warnings

Therapeutic duplication is the use of more than one medicine from the same drug category or therapeutic class to treat the same condition. This can be intentional in cases where drugs with similar actions are used together for demonstrated therapeutic benefit. It can also be unintentional in cases where a patient has been treated by more than one doctor, or had prescriptions filled at more than one pharmacy, and can have potentially adverse consequences.

Duplication

Agents for pulmonary hypertension

Therapeutic duplication

The recommended maximum number of medicines in the 'agents for pulmonary hypertension' category to be taken concurrently is usually one. Your list includes two medicines belonging to the 'agents for pulmonary hypertension' category:

  • riociguat
  • tadalafil

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.

See also

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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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