Archives
Safety and drug interactions
As with every PDE5 inhibitor, tadalafil is absolutely contraindicated with nitrate medications for angina pectoris secondary to the potentiated hypotensive effect the drugs can have together. Because of the longer half-life, treatment with nitrate medications must be deferred for at least 48 hours after ingestion of tadalafil, compared with 24 hours for sildenafil (Viagra) and [...]
Adverse events
A large study of 2102 men from 11 different multicentered, randomized, double-blind, placebo controlled trials of tadalafil reported the drug is well tolerated overall. Fifty-one percent of men using tadalafil 20 mg had at least one adverse event (AE), but only 3.2% discontinued treatment. The most common AEs reported with the 20 mg dose were [...]
Difficult-to-treat ED
In the two trials mentioned in the previous section, the patient population was largely a primary care population of relatively healthy men with ED of varying severities and etiologies. To the contrary, a multicentered, randomized, double-blind, placebo controlled trial evaluated how tadalafil 20 mg improved ED in men presenting to tertiary care centers with more [...]
Metabolism and excretion
The metabolism of generic tadalafil is via the hepatic enzyme cytochrome P450 34A (CYP34A) to a catechol metabolite, which undergoes further metabolism to its primary circulating metabolite, methylcatechol glucuronide, a 10,000-fold less potent molecule than tadalafil. The CYP34A metabolism pathway of tadalafil was verified with studies using a CYP34A inhibitor ketoconazole and a CYP34A inducer [...]
The general ED population
The most frequently referenced study supporting the efficacy of tadalafil is an integrated analysis of 5 randomized, double-blind, placebo controlled, multicentered phase III trials from 1112 men at 74 centers worldwide. The average age was 59, and the etiology of ED was 61% organic, 9% psychogenic, and 31% mixed. The ED severity at baseline was [...]
Duration of action
Among the three PDE5 inhibitors, the half-life and thus duration of action is the pharmacologic parameter that is the most strikingly dissimilar. The half-life of tadalafil is 17.5 hours in normal healthy men and 21.6 hours in elderly men, while the half-lives of sildenafil and vardenafil are similar at 4 hours. This longer half-life provides [...]
Dosing and absorption Tadalafil (Cialis)
Recommended starting doses of tadalafil are 10 mg for on-demand dosing and 2.5 mg for once-daily dosing, and these doses can then be titrated up or down according to the efficacy and tolerability. It is absorbed as a low-solubility and high-permeability, or Class 2, drug within the FDA Biopharmaceuticals Classification System. With oral ingestion, after [...]
