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Drug Interactions between OraVerse and sildenafil

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

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Interactions between your drugs

Moderate

phentolamine sildenafil

Applies to: OraVerse (phentolamine) and sildenafil

MONITOR: Concurrent use of a phosphodiesterase-5 (PDE5) inhibitor with phentolamine may result in additive adverse effects resulting from both medications acting as vasodilators. Additional factors may affect the severity of this interaction including the route of administration, dosing regimen, amount of each medication absorbed systemically, presence of intravascular depletion, and use of other medications with hypotensive effects. Reductions of systolic BP ranging from 2.5 mmHg to greater than 30 mmHg from baseline have been reported with alfuzosin, doxazosin, tamsulosin and/or terazosin. However, data are not available for all formulations of phentolamine. There are studies which evaluate the combination of intracavernosal injections (ICIs) containing phentolamine with an oral PDE5 inhibitor for erectile dysfunction (ED). In one case series, 93 patients were treated for ED with sildenafil monotherapy or sildenafil in combination with ICI triple-therapy after failing a trial of ICI (monotherapy or triple therapy). Those who received sildenafil in combination with ICI triple-therapy (n=41) reported an increase in adverse effects (e.g., dizziness, syncope) when compared to monotherapy (49% with combination therapy vs. 31% with ICI alone and 37% with sildenafil alone).

MANAGEMENT: Caution and clinical monitoring for adverse effects (e.g., hypotension, dizziness, syncope, priapism) are advised if phentolamine is used in combination with a PDE5 inhibitor. Some manufacturers (both of PDE5 inhibitors as well as of phentolamine) advise against combining treatments for ED due to a lack of safety and efficacy data. However, there are guidelines specific to the treatment of ED which contain guidance for using an oral PDE5 inhibitor with ICIs containing phentolamine (though this may be an off-label indication for phentolamine). The severity of this interaction may be affected by additional factors listed above. In general, most product labeling recommends stabilizing a patient on either alpha-blocker therapy or PDE5 inhibitor therapy first and then initiating the other medication with the knowledge that increases in dosage may result in further lowering of blood pressure. If combination therapy is used, consultation with product labeling and relevant treatment guidelines as well as counseling the patient on potential adverse effects is recommended.

References

  1. "Product Information. Adcirca (tadalafil)." United Therapeutics Corporation (2009):
  2. "Product Information. Stendra (avanafil)." Vivus Inc (2012):
  3. "Product Information. Staxyn (vardenafil)." Merck & Co., Inc (2014):
  4. "Product Information. Liqrev (sildenafil)." Carolina Medical Products Company (2023):
  5. "Product Information. Silcap (sildenafil)." iX Biopharma Pty Ltd (2021):
  6. "Product Information. Revatio (sildenafil)." Pfizer Ltd (2023):
  7. "Product Information. Invicorp (aviptadil-fentolamin)." Evolan Pharma AB (2023):
  8. Dhir RR, Lin HC, Canfield SE, Wang R "Combination therapy for erectile dysfunction: an update review." Asian J Androl 13 (2011): 382-90
  9. Al-Adl AM, Abdel-Wahab O, El-Karamany T, Aal AA "Combined intracavernous vasoactive drugs and sildenafil citrate in treatment of severe erectile dysfunction not responding to on-demand monotherapy." Arab J Urol 9 (2011): 153-8
  10. Karakus S, Burnett AL "The medical and surgical treatment of erectile dysfunction: a review and update. https://www.canjurol.com/abstract.php?ArticleID=&version=1.0&PMID=32876000" (2024):
  11. Burnett AL, Nehra A, Breau RH, et al. "Erectile Dysfunction: AUA Guideline." J Urol 200 (2018): 633-41
  12. Hackett G, Kirby M, Wylie K, et al. "British society for sexual medicine guidelines on the management of erectile dysfunction in men - 2017." J Sex Med 15 (2018): 430-57
  13. Lowy M, Ramanathan V "Erectile dysfunction: causes, assessment and management options. https://australianprescriber.tg.org.au/articles/erectile-dysfunction-causes-assessment-and-management-options.html" (2024):
  14. Domes T, Najafabadi BT, Roberts M, et al. "Canadian urological association guideline: erectile dysfunction." Can Urol Assoc J 10 (2021): 310-22
View all 14 references

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Drug and food interactions

Moderate

sildenafil food

Applies to: sildenafil

GENERALLY AVOID: Coadministration with grapefruit juice may slightly increase the oral bioavailability and delay the onset of action of sildenafil. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. In a randomized, crossover study with 24 healthy male volunteers, ingestion of 250 mL of grapefruit juice one hour before and concurrently with a 50 mg dose of sildenafil increased the mean area under the plasma concentration-time curve (AUC) of sildenafil and its pharmacologically active N-desmethyl metabolite by 23% and 24%, respectively, compared to water. Peak plasma concentrations (Cmax) were unaltered, but the time to reach sildenafil Cmax was prolonged by 0.25 hour. The observed increase in sildenafil bioavailability is unlikely to be of clinical significance in most individuals. However, pharmacokinetic interactions involving grapefruit juice are often subject to a high degree of interpatient variability and may be significant in the occasional susceptible patient. Indeed, one subject in the study had a 2.6-fold increase in sildenafil concentrations.

MANAGEMENT: It may be advisable to avoid administration of sildenafil with grapefruit juice to prevent potential toxicity and delay in onset of action.

References

  1. Jetter A, Kinzig-Schippers M, Walchner-Bonjean M, et al. "Effects of grapefruit juice on the pharmacokinetics of sildenafil." Clin Pharmacol Ther 71 (2002): 21-29

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Moderate

phentolamine food

Applies to: OraVerse (phentolamine)

MONITOR: Many psychotherapeutic and CNS-active agents (e.g., anxiolytics, sedatives, hypnotics, antidepressants, antipsychotics, opioids, alcohol, muscle relaxants) exhibit hypotensive effects, especially during initiation of therapy and dose escalation. Coadministration with antihypertensives and other hypotensive agents, in particular vasodilators and alpha-blockers, may result in additive effects on blood pressure and orthostasis.

MANAGEMENT: Caution and close monitoring for development of hypotension is advised during coadministration of these agents. Some authorities recommend avoiding alcohol in patients receiving vasodilating antihypertensive drugs. Patients should be advised to avoid rising abruptly from a sitting or recumbent position and to notify their physician if they experience dizziness, lightheadedness, syncope, orthostasis, or tachycardia.

References

  1. Sternbach H "Fluoxetine-associated potentiation of calcium-channel blockers." J Clin Psychopharmacol 11 (1991): 390-1
  2. Shook TL, Kirshenbaum JM, Hundley RF, Shorey JM, Lamas GA "Ethanol intoxication complicating intravenous nitroglycerin therapy." Ann Intern Med 101 (1984): 498-9
  3. Feder R "Bradycardia and syncope induced by fluoxetine." J Clin Psychiatry 52 (1991): 139
  4. Ellison JM, Milofsky JE, Ely E "Fluoxetine-induced bradycardia and syncope in two patients." J Clin Psychiatry 51 (1990): 385-6
  5. Rodriguez de la Torre B, Dreher J, Malevany I, et al. "Serum levels and cardiovascular effects of tricyclic antidepressants and selective serotonin reuptake inhibitors in depressed patients." Ther Drug Monit 23 (2001): 435-40
  6. Cerner Multum, Inc. "Australian Product Information." O 0
  7. Pacher P, Kecskemeti V "Cardiovascular side effects of new antidepressants and antipsychotics: new drugs, old concerns?" Curr Pharm Des 10 (2004): 2463-75
  8. Andrews C, Pinner G "Postural hypotension induced by paroxetine." BMJ 316 (1998): 595
View all 8 references

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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

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