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Drug Interactions between trimethaphan camsylate and Viagra

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

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Interactions between your drugs

Moderate

trimethaphan camsylate sildenafil

Applies to: trimethaphan camsylate and Viagra (sildenafil)

MONITOR: Phosphodiesterase-5 (PDE5) inhibitors may potentiate the blood pressure-lowering effect of antihypertensive medications, including vasodilators. These agents inhibit PDE5-mediated degradation of cyclic guanosine monophosphate (cGMP), which in vascular smooth muscles can lead to peripheral vasodilation and thus blood pressure (BP) reduction. For example, when sildenafil (100 mg) was coadministered with amlodipine (5 mg or 10 mg) to hypertensive patients, the mean additional reduction in supine BP was 8/7 mmHg. Likewise, in a group of patients whose hypertension was controlled with nifedipine slow-release (30 mg or 60 mg) once daily, the addition of vardenafil (20 mg) produced a mean additional supine BP reduction of 6/5 mmHg compared to placebo. When coadministered with amlodipine (5 mg) daily or enalapril (20 mg) daily, a single dose of avanafil (200 mg) produced a mean maximum decrease in supine systolic BP of 1.2 mmHg (amlodipine) and supine BP of 1.8/3.5 mmHg (enalapril) compared to placebo.

MANAGEMENT: Caution is advised if PDE5 inhibitors are prescribed in combination with antihypertensive agents. Patients receiving the combination should be advised to avoid rising abruptly from a sitting or recumbent position, especially following treatment initiation or a dosage increase, and to contact their doctor if they experience symptoms of hypotension such as dizziness, lightheadedness, fainting, or tachycardia.

References

  1. "Product Information. Viagra (sildenafil)." Pfizer U.S. Pharmaceuticals PROD (2001):
  2. "Product Information. Levitra (vardenafil)." Bayer (2003):
  3. "Product Information. Stendra (avanafil)." Vivus Inc (2012):

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Drug and food interactions

Moderate

sildenafil food

Applies to: Viagra (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

trimethaphan camsylate food

Applies to: trimethaphan camsylate

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.

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

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