Is Phentolamine Stable in Solution with Papaverine

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Abstract
Although the intracorporeal injection of mixtures of phentolamine and papaverine is used commonly in the diagnosis and treatment of erectile dysfunction, pharmacological data relating to the stability of such drug mixtures are lacking. The stability of phentolamine mesylate in aqueous solution and in solution with papaverine (0.83 mg. per cc phentolamine and 25 mg. per cc papaverine) was ascertained by high performance liquid chromatography and gas chromatography with mass spectrometry. No degradation of phentolamine occurred during 40 days whether the drug or drug combination was refrigerated or stored at room temperature. Phentolamine is stable for at least 40 days when mixed with papaverine.