STAXYN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for STAXYN (STAXYN).
Selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5). By inhibiting PDE5, sildenafil increases intracellular cGMP levels in the corpus cavernosum, enhancing the relaxant effect of nitric oxide (NO) on smooth muscle cells, thereby facilitating penile erection in response to sexual stimulation.
| Metabolism | Primarily metabolized by hepatic CYP3A4 (major) and CYP2C9 (minor) isoenzymes. The major metabolite is N-desmethyl sildenafil, which has a PDE5 selectivity profile similar to the parent drug and contributes to the pharmacological activity. |
| Excretion | Renal (approximately 90% as metabolites, <2% unchanged); fecal (10%) |
| Half-life | Terminal elimination half-life is approximately 4-5 hours; clinically, no accumulation with once-daily dosing |
| Protein binding | 96% bound to plasma proteins (albumin and alpha-1 acid glycoprotein) |
| Volume of Distribution | Approximately 2 L/kg; suggests extensive tissue distribution |
| Bioavailability | 41% (oral); increased to 71% when taken with a high-fat meal |
| Onset of Action | Orally disintegrating tablet: 14-60 minutes |
| Duration of Action | Up to 4 hours; sexual stimulation is required for effect |
10 mg sublingually as needed, 30–60 minutes before sexual activity. Maximum 1 dose per 24 hours.
| Dosage form | TABLET, ORALLY DISINTEGRATING |
| Renal impairment | No adjustment for mild to moderate impairment. Not recommended for severe renal impairment (CrCl <30 mL/min). |
| Liver impairment | Contraindicated in severe hepatic impairment (Child-Pugh class C). For mild to moderate (Child-Pugh A or B), no adjustment but caution advised. |
| Pediatric use | Not indicated in pediatric patients (age <18 years). |
| Geriatric use | No adjustment required for elderly; consider lower starting dose (5 mg) in patients >65 years due to decreased clearance. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for STAXYN (STAXYN).
| Breastfeeding | Unknown if vardenafil is excreted in human milk. M/P ratio not determined. Caution advised; discontinue nursing or drug due to risk of adverse effects in infant. |
| Teratogenic Risk | FDA Pregnancy Category B. No evidence of teratogenicity in animal studies; no adequate human studies in first trimester. Caution in second and third trimesters due to potential for uterine hyperstimulation and fetal distress associated with vasodilation. |
| Fetal Monitoring |
■ FDA Black Box Warning
None
| Serious Effects |
["Concomitant use of nitrates (organic nitrates, nitric oxide donors) in any form (regular or intermittent).","Concomitant use of guanylate cyclase stimulators (e.g., riociguat).","Known hypersensitivity to sildenafil or any excipient of the formulation.","Patients with severe hepatic impairment (Child-Pugh class C).","Patients with end-stage renal disease requiring dialysis.","Patients with hypotension (BP <90/50 mmHg) or uncontrolled hypertension (BP >170/100 mmHg).","Patients with a history of non-arteritic anterior ischemic optic neuropathy (NAION) (temporary association)."]
| Precautions | ["Risk of priapism: erections lasting >4 hours require immediate medical attention.","Co-administration with alpha-blockers may cause symptomatic hypotension.","Not recommended in patients with pulmonary veno-occlusive disease.","Use with caution in patients with anatomical deformation of the penis (angulation, cavernosal fibrosis, Peyronie's disease).","Cardiovascular risk: sexual activity may pose a risk in patients with underlying cardiovascular disease."] |
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| Monitor maternal blood pressure and heart rate during use. Assess fetal heart rate if used for erectile dysfunction during pregnancy (off-label). Uterine monitoring may be warranted due to risk of hyperstimulation. |
| Fertility Effects | No known adverse effects on fertility in animal studies. In humans, vasodilation may impair erectile function, but no direct effect on spermatogenesis or ovarian function has been reported. |