Sildenafil Citrate Dosage Forms and Available Strengths
[8] It can be taken orally (swallowed by mouth), intravenously (injection into a vein), or through the sublingual route (dissolved under the tongue). [8][10] Onset when taken orally is typically within twenty minutes and lasts for about two hours. Common side effects include headaches, heartburn, and flushed skin. [8] Caution is advised in those with cardiovascular disease.
What happens if I overdose?
Data from a case report describe the presence of sildenafil and its active metabolite in human milk. There is insufficient information on the effects of sildenafil on the breast-fed infant and no information on the effects of sildenafil on milk production. Sildenafil, sold under the brand name Viagra among others, is a medication used to treat erectile dysfunction and pulmonary arterial hypertension. [4][8] It is also sometimes used off-label for the treatment of certain symptoms in secondary Raynaud's phenomenon. [9] It is unclear if it is effective for treating sexual dysfunction in females. [8] Rare but serious side effects include vision problems, hearing loss, and prolonged erection (priapism) that can lead to damage to the penis. [8] Sildenafil should not be taken by people on nitric oxide donors such as nitroglycerin, as this may result in a serious drop in blood pressure. Sildenafil acts by blocking phosphodiesterase 5 (PDE5), an enzyme that promotes breakdown of cGMP, which regulates blood flow in the penis. [8] It requires sexual arousal to work, and does not by itself cause or increase sexual arousal.
| Product | Dosage | Quantity + Bonus | Price | |
|---|---|---|---|---|
| Kamagra Soft Tabs | 100mg | 120 + 6 Pills | 311.78€ 296.93€ | |
| Viagra Generic | 200mg | 10 Pills | 40.96€ 39.01€ | |
| Viagra Generic | 100mg | 180 + 8 Pills | 199.37€ 189.88€ | |
| Kamagra Soft Tabs | 100mg | 60 + 4 Pills | 180.59€ 171.99€ | |
| Viagra Generic | 200mg | 120 + 8 Pills | 204.80€ 195.05€ | |
| Kamagra Polo | 100mg | 12 Pills | 60.21€ 57.34€ | |
| Viagra Generic | 100mg | 120 + 6 Pills | 149.50€ 142.38€ | |
| Viagra Generic | 100mg | 90 + 6 Pills | 129.02€ 122.88€ | |
| Kamagra | 100mg | 360 + 6 Pills | 839.95€ 799.95€ | |
| Viagra Generic | 150mg | 30 + 2 Pills | 72.32€ 68.88€ | |
| Kamagra Polo | 100mg | 32 Pills | 125.88€ 119.89€ |
[8] It also results in dilation of the blood vessels in the lungs. Pfizer originally discovered the medication in 1989 white sildenafil tablets while looking for a treatment for angina. [11] It was approved for medical use in the United States and in the European Union in 1998.
| Effect | Mechanism | Onset Time | Duration |
|---|---|---|---|
| Vasodilation | Increased cGMP in smooth muscle | 30 mins | 4-6 hours |
| Blood Pressure Reduction | Vasodilation effects | Rapid | Several hours |
| Enhanced Erectile Function | Increased blood flow to penis | 30 mins | Up to 4-6 hours |
[5][8][11][12] In 2023, it was the 151st most commonly prescribed medication in the United States, with more than 3 million prescriptions. [13][14] It is available as a generic medication. [15][16] In the United Kingdom, it is available as a pharmacy medicine.
Are There Any Side Effects?
Sildenafil enhances the effect of NO by inhibiting PDE5 thereby raising concentrations of cGMP in the corpus cavernosum. Sildenafil has no direct relaxant effect on isolated human corpus cavernosum and, at recommended doses, has no effect in the absence of sexual stimulation. As reported by the manufacturer, the pharmacodynamic response to sildenafil was assessed in eight double-blind, placebo-controlled crossover studies of patients with either organic or psychogenic erectile dysfunction. In these studies sexual stimulation resulted in improved erections, as assessed by penile plethysmography, after sildenafil administration compared with placebo. Most studies evaluated the efficacy of sildenafil approximately 60 minutes post dose.
Vybrique Oral Film
The erectile response, as determined by penile plethysmography, generally increased with increasing sildenafil dose and plasma concentration. The time course of effect was examined in one study. The effects of sildenafil were evident for up to 4 hours, but the response was diminished compared to 2 hours.In vitro studies show that sildenafil is selective for PDE5 and its effect is more potent on PDE5 than on other known phosphodiesterases. The approximately 4,000-fold selectivity for PDE5 versus PDE3 is important because PDE3 is involved in control of cardiac contractility. Sildenafil can also inhibit PDE5 present in esophageal smooth muscle, lung tissue, and brain tissue. The primary indication of sildenafil is treatment of erectile dysfunction (inability to sustain a satisfactory erection to complete sexual intercourse). Its use is now one of the standard treatments for erectile dysfunction, including for males with diabetes mellitus.
Other uses for this medicine
Dosage reductions are recommended for patients receiving potent cytochrome CYP3A4 inhibitors. Sildenafil is rapidly absorbed after oral administration, with a mean absolute bioavailability sildenafil 100 mg cost of about 41% (25% to 63%). Its pharmacokinetics are dose-proportional over the recommended dose range. Maximum observed plasma concentrations are reached within 30 to 120 minutes (median 60 minutes) of oral dosing in the fasted state. Oral Suspension (Liqrev):When sildenafil is taken with a high fat meal, the rate of absorption is reduced, with a mean delay in Tmax of 60 minutes and a mean reduction in Cmax of 53%; the extent of absorption (AUC) is increased by 11%.Oral tablets and oral powder for suspension (Revatio, Viagra):When sildenafil is taken with a high fat meal, the rate of absorption is reduced, with a mean delay in Tmax of 60 minutes and a mean reduction in Cmax of 29%.
Sildenafil may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
A 10 mg IV dose is predicted to provide a pharmacological effect of sildenafil and its N-desmethyl metabolite equivalent to that of a 20 mg PO dose. Limited data do not report a clear association with the use of sildenafil and major birth defects, miscarriage, or adverse maternal or fetal outcomes when sildenafil is used during pregnancy. No evidence of teratogenicity or embryofetal toxicity was observed in animal reproduction studies using sildenafil at doses 32- and 65-times the recommended human dose. There are risks to the mother and fetus from untreated pulmonary arterial hypertension. Limited clinical data preclude a clear determination of the risk of sildenafil to an infant during breast-feeding. Tentative evidence suggests that sildenafil may help males who experience antidepressant-induced erectile dysfunction.
| Use | Evidence Level | Description | Caution |
|---|---|---|---|
| Altitude Sickness | Experimental | Vasodilation might improve oxygenation | Not FDA approved, consult specialist |
| Premature Ejaculation | Anecdotal evidence | Local vasodilation effects may extend ejaculatory latency | Limited data |
| Cold-induced Vasospasm | Off-label | May alleviate symptoms of vasospasm | Requires medical supervision |
While sildenafil improves some markers of disease in people with pulmonary arterial hypertension, it does not appear to affect the risk of death or serious side effects. Sildenafil and other PDE5 inhibitors are used off-label to alleviate vasospasm and treat severe ischemia and ulcers in fingers and toes for people with secondary Raynaud's phenomenon;[9][21] these drugs have moderate efficacy for reducing the frequency and duration of vasospastic episodes.
- Sildenafil citrate was approved by the FDA in 1998.
- Its discovery revolutionized the treatment of erectile dysfunction.
- The medication requires sexual stimulation to be effective.
- It is not an aphrodisiac; it facilitates natural response.
- Overdose symptoms may include severe hypotension.
- Recreational use of sildenafil without prescription is risky.
- Combining with alcohol can increase side effects.
- It should be stored at room temperature away from moisture.
[9] As of 2016,[update] their role more generally in Raynaud's was not clear. Sildenafil has shown some potential for improving exercise performance at high altitudes. However, its overall efficacy is not clear. Sildenafil has been studied for high-altitude pulmonary edema (HAPE), but its use is currently not recommended for that indication.
What should I do if I forget a dose?
Inhibition of PDE5 in lung tissue results in relaxation of pulmonary vascular smooth muscle and subsequently pulmonary vasodilation, thereby making sildenafil an effective agent in treating pulmonary hypertension. Inhibition of PDE5 present in esophageal smooth muscle can cause a marked inhibition of esophageal motility as well as a reduction in lower esophageal sphincter (LES) tone. These effects may be beneficial in certain motor disorders involving the esophagus such as diffuse spasm, nutcracker esophagus, and hypertensive LES. However, the reduction in LES tone can worsen the symptoms of gastroesophageal reflux disease (GERD). Sildenafil is one-tenth as potent for PDE6, an enzyme found in the retina, as it is for PDE5; this lower selectivity is thought to be the basis for abnormalities related to color vision observed with higher doses or plasma concentrations of the drug.
Statistical Analysis
The mean steady state volume of distribution (Vss) is 105 L, indicating widespread tissue distribution. Sildenafil and its major circulating N-desmethyl metabolite are both approximately 96% bound to plasma proteins. Protein binding is independent of total drug concentrations. Based upon measurements of sildenafil in semen of healthy volunteers 90 minutes after dosing, less than 0.001% of the administered dose may appear in the semen of patients. Sildenafil is predominantly metabolized by hepatic cytochrome P450 (CYP) enzymes. In clinical trials, the most common adverse effects of sildenafil use included headache, flushing, indigestion, nasal congestion, and impaired vision, including photophobia and blurred vision.
- Sildenafil can cause sudden vision loss (rare side effect).
- Men with a history of retina problems should use caution.
- It may cause a drop in blood pressure, leading to dizziness.
- Patients should report any persistent erection lasting over 4 hours.
- It is crucial to have proper medical evaluation before use.
- Not suitable for individuals with severe liver or kidney conditions.
- The medication is also investigated for breast cancer treatment.
- Proper hydration can help minimize some side effects.
[4] Some sildenafil users have complained of seeing everything tinted blue (cyanopsia).
| Condition | Temperature Range | Light Exposure | Additional Notes |
|---|---|---|---|
| General storage | 20-25°C (68-77°F) | Keep in original container | Avoid moisture and heat |
| Refrigeration | Not required | No | If needed, store in fridge |
| Avoid exposure | Humidity, direct sunlight | Yes | To preserve potency |
[24] This cyanopsia can be explained because sildenafil, while selective for PDE5, does have some affinity for PDE6, which is the phosphodiesterase found in the retina.
Mechanism of action
One active metabolite with properties similar to the parent drug has been identified and is formed by N-desmethylation of sildenafil. This metabolite has a PDE selectivity profile similar to sildenafil and an in vitro potency for PDE5 approximately 50% of the parent drug. Plasma concentrations of this metabolite are approximately 40% of those seen for sildenafil and accounts for about 20% of the pharmacologic effects of sildenafil. However, the ratio of the metabolite to sildenafil is higher in patients with pulmonary arterial hypertension (PAH). The metabolite is further metabolized to inactive compounds.
Interactions that increase your risk for side effects
Sildenafil is excreted as metabolites primarily in the feces (approximately 80% of administered oral dose) and to a lesser extent in the urine (approximately 13% of the administered oral dose). Both sildenafil and its active metabolite have terminal half-lives of about 4 hours. Sildenafil concentrations at 24 hours post a single 100 mg oral dose average 2 ng/mL (compared to peak plasma concentrations of approximately 440 ng/mL). While similar pharmacokinetic parameters were observed in healthy volunteers and patients with erectile dysfunction, the average steady-state concentrations were 20% to 50% higher and Cmin levels doubled in patients with PAH compared to healthy volunteers. Affected cytochrome P450 isoenzymes: CYP3A4 and CYP2C9Sildenafil is metabolized principally by the hepatic cytochrome P450 (CYP) 3A4; CYP2C9 is also involved to a lesser degree. Patients thus taking the drug may experience colorvision abnormalities. Some complained of blurriness and loss of peripheral vision. In July 2005, the US Food and Drug Administration (FDA) updated labeling for tadalafil (Cialis), vardenafil (Levitra), and sildenafil (Viagra) to reflect a small number of post-marketing reports of sudden vision loss, while acknowledging that "...it is not possible to determine whether these oral medicines for erectile dysfunction were the cause of the loss of eyesight or whether the problem is related to other factors such as high blood pressure or diabetes, or to a combination of these problems.