1.Investigating the degradation of the sympathomimetic drug phenylephrine by electrospray ionisation-mass spectrometry.
Trommer H1, Raith K, Neubert RH. J Pharm Biomed Anal. 2010 Jun 5;52(2):203-9. doi: 10.1016/j.jpba.2010.01.024. Epub 2010 Jan 20.
The frequently used sympathomimetic drug phenylephrine has been studied by electrospray ionisation-mass spectrometry. The stability of the adrenoceptor agonist was examined by investigations of the pharmaceutically used salts phenylephrine hydrochloride and phenylephrine bitartrate. Photostability has been studied by use of an irradiation equipment emitting a solar radiation spectrum. The experiments were carried out by analysis of aqueous drug solutions before and after irradiation treatment. The phenylephrine derivative with unsaturated side chain originating from the drug by loss of one water molecule has been detected as the major degradation product of both phenylephrine salts the hydrochloride and the bitartrate. Further degradation and oxidation products were detectable already in the full scan mode demonstrating a low stability of the drug. Tandem mass spectrometry and multiple stage mass spectrometry experiments enabled the establishment of fragmentation schemes of both salts for the first time.
2.[Effects of testosterone on smooth muscle in the isolated rabbit corpus cavernosum penis].
Baba K1. Nihon Hinyokika Gakkai Zasshi. 1993 Oct;84(10):1783-90.
It has been reported that there is no relationship between serum testosterone level and erectile function and that testosterone mainly acts on the brain and not on the penis. However, we have found that erectile dysfunction in some patients with low serum testosterone improved after androgen replacement therapy. We therefore studied the effects of testosterone on the contraction and relaxation of the corpus cavernosum penis. Four groups of rabbits were studied over a similar time span. The testosterone group were non-operated and received testosterone propionate 10 mg/day for 14 days before sacrifice. Two groups (castration+testosterone group and castration group) were castrated 28 days before sacrifice. The castration group received sesame oil for 14 days, and the castration+testosterone group received testosterone 10 mg/day for 14 days. Entire penis were removed immediately after death by desanguination and dissected to obtain corpus cavernosum strips.
3.Alpha-adrenoceptors in equine digital veins: evidence for the presence of both alpha1 and alpha2-receptors mediating vasoconstriction.
Elliott J1. J Vet Pharmacol Ther. 1997 Aug;20(4):308-17.
Rings of equine digital vein examined under conditions of isometric tension recording constricted to alpha-adrenoceptor agonists with an order of potency of 5-bromo-6-[2-imidazolin-2-yl-amino]-quinoxaline bitartrate (UK 14304) = noradrenaline > 6-Allyl-2-amino-5,6,7,8-tetrahydro-4H-thiazolo-(4,5-d) azepine (BHT-920) > phenylephrine > dopamine > methoxamine. The maximum force generated was greatest for the non-selective agonist noradrenaline and lowest for the alpha2-selective agonist BHT-920 with the other agonists between these two extremes. Selective inactivation of alpha1-adrenoceptors (achieved by treating yohimbine-protected tissues with phenoxybenzamine) reduced the maximum responses of all agonists, the EC50 values of UK 14304, BHT-920 and noradrenaline and increased the EC50 values of phenylephrine and methoxamine. Prazosin (30 nM) had no inhibitory effect on responses to low concentrations of BHT-920 and UK 14304 and caused competitive inhibition of responses to phenylephrine and noradrenaline giving pKb values of 8.
4.Cold, cough, allergy, bronchodilator, and antiasthmatic drug products for over-the-counter human use; amendment of monograph for OTC nasal decongestant drug products. Final rule.
Fed Regist. 2006 Aug 1;71(147):83358[sic., should be 43358]-63.
The Food and Drug Administration (FDA) is issuing a final rule to amend the final monograph (FM) for over-the-counter (OTC) nasal decongestant drug products (drug products used to relieve nasal congestion due to a cold, hay fever, or other upper respiratory allergies) to add phenylephrine bitartrate (PEB), both individually and in combination drug products in an effervescent dosage form, as generally recognized as safe and effective (GRASE). An effervescent dosage form is intended to be dissolved in water before taking by mouth. This final rule is part of FDA's ongoing review of OTC drug products.