medinfo (![[info]](http://l-stat.livejournal.com/img/userinfo.gif){kind=small} medinfo) wrote,@ 2005-10-28 05:59:00 |
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New oral drugs for erectile dysfunction.
New oral drugs for erectile dysfunction.
In 1998, we concluded that sildenafil (Viagra--fizer Ltd), a selective phosphodiesterase type 5 inhibitor, appeared to offer advantages over other medical approaches for erectile dysfunction in terms of ease of administration and cost. Oral drug treatment is now widely advocated as first-line therapy for erectile dysfunction, except where the cause is clearly psychological. In the past 4 years, three more oral preparations have been licensed in the UK for the treatment of men with erectile dysfunction. A sublingual preparation of the dopaminergic agonist apomorphine (Uprima--Abbott Laboratories Ltd) is the first centrally acting drug to be licensed. Tadalafil (Cialis--Eli-Lilly) and vardenafil (Levitra--Bayer PLC) are phosphodiesterase type 5 inhibitors. Here we review the place of these preparations for men with erectile dysfunction.
Journal ISSN: 0012-6543 Issue: 42-7 (2004) Pages: 49-52
Vardenafil: structural basis for higher potency over sildenafil in inhibiting cGMP-specific phosphodiesterase-5 (PDE5).
Vardenafil: structural basis for higher potency over sildenafil in inhibiting cGMP-specific phosphodiesterase-5 (PDE5).
Phosphodiesterase-5 (PDE5) inhibitors act by competing with the substrate, cGMP, for the catalytic site of the enzyme. Two commercialized PDE5 inhibitors, sildenafil and vardenafil, are being used to treat erectile dysfunction. These two compounds differ in the heterocyclic ring system used to mimic the purine ring of cGMP. They also differ in the substituent (ethyl/methyl) of a piperazine side chain. Although these are the only two structural differences, vardenafil has more than 20-fold greater potency than sildenafil for inhibiting purified PDE5. The molecular structural basis for the difference in potency of the two compounds was investigated by synthesizing an analog of sildenafil ("methyl-sildenafil") that contained the sildenafil ring system but with the appended ethyl group found in vardenafil, and an analog of vardenafil ("demethyl-vardenafil") that contained the vardenafil ring system but with the appended methyl group found in sildenafil. The IC50 of methyl-sildenafil for inhibiting PDE5 indicated that it was 64 times less potent than demethyl-vardenafil, which was similar to the finding that, based on IC50, sildenafil was 40 times less potent than vardenafil. Similarly, the EC50 of methyl-sildenafil for inhibiting [3H]vardenafil binding to PDE5 indicated that it was 84 times less potent than demethyl-vardenafil, while the EC50 for sildenafil indicated that it was 31 times less potent than vardenafil. It is concluded that the methyl/ethyl appended group on the piperazine moiety plays very little role in the difference in potency between sildenafil and vardenafil for inhibiting PDE5, whereas the differences in the ring systems play a critical role in higher potency of vardenafil over sildenafil.
Journal ISSN: 0197-0186 Issue: 45-6 (2004) Pages: 859-63
Urological manifestations of vascular disease.
Urological manifestations of vascular disease.
We have detailed several of the urological manifestations of vascular disease. With the aging of the North American population, urologists will encounter the urological complications of vascular disease with ever-increasing frequency.
Journal ISSN: 0094-0143 Issue: 30-1 (2003) Pages: 13-26
A new synthesis of carboxyterfenadine (fexofenadine) and its bioisosteric tetrazole analogs.
A new synthesis of carboxyterfenadine (fexofenadine) and its bioisosteric tetrazole analogs.
A new synthesis of carboxyterfenadine (4), based on the conversion of a alpha-halo-alkylarylketone into the corresponding substituted 2-arylalkanoic ester, is described. The enantioselective synthesis of its two bioisosteric tetrazole analogs together with preliminary biological results are reported.
Journal ISSN: 0014-827X Issue: 54-9 (1999) Pages: 600-10
Desloratadine has no clinically relevant electrocardiographic or pharmacodynamic interactions with ketoconazole.
Desloratadine has no clinically relevant electrocardiographic or pharmacodynamic interactions with ketoconazole.
OBJECTIVE: This study was performed to assess the electrocardiographic safety and pharmacokinetics of desloratadine in combination with the CYP3A4 inhibitor ketoconazole. DESIGN: A randomised, placebo-controlled, third-party-blind, 2-way crossover study. PARTICIPANTS: 24 healthy volunteers (12 men, 12 women; age 19 to 50 years). INTERVENTIONS: 7.5mg of desloratadine orally per day in combination with placebo or with 200mg of ketoconazole every 12 hours for 10 days. After a minimum 7-day washout period, participants received the alternative treatment. MAIN OUTCOME MEASURES: ECG parameters. RESULTS: Comparable maximum corrected QT (QT(c)) intervals were observed after coadministration of desloratadine and placebo or ketoconazole (431 and 435 msec, respectively). The desloratadine/ketoconazole combination did not induce any statistically significant or clinically relevant changes in QT(c), QT, PR or QRS intervals compared with desloratadine alone; ventricular rate was slightly slower when desloratadine was given with ketoconazole. At steady state, coadministration of ketoconazole resulted in no significant change in area under the desloratadine concentration-time curve (AUC) from 0 to 24 hours compared with desloratadine/placebo. Coadministration of desloratadine and ketoconazole resulted in a 1.3-fold increase in desloratadine maximum concentration (C(max)) that was not clinically relevant. The most common adverse event was headache, reported in 42 and 38% of individuals, respectively, after coadministration of desloratadine/placebo and desloratadine/ketoconazole. There were no reports of dizziness or syncope. CONCLUSION: Coadministration of desloratadine and ketoconazole was well tolerated and was associated with minimal increase in AUC and C(max). The combination did not induce any clinically relevant electrocardiographic changes.
Journal ISSN: 0312-5963 Issue: 41 Suppl 1- (2002) Pages: 37-44
