Limited clinical data preclude a clear determination of the risk of sildenafil to an infant during breast-feeding.
What Other Drugs Interact with Sildenafil?
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. Dosage reductions are recommended for patients receiving potent cytochrome CYP3A4 inhibitors. Sildenafil is rapidly absorbed after oral administration, with a mean absolute bioavailability 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.
Taking Viagra with food
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%. 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. Data from a case report describe the presence of sildenafil and its active metabolite in human milk.
| Parameter | Description | Typical Value |
|---|---|---|
| Absorption Rate | Time to reach peak plasma concentration | 30-120 minutes |
| Bioavailability | Percentage of dose reaching systemic circulation | 40% |
| Half-life | Time to reduce plasma concentration by half | 4 hours |
| Metabolism | Primary site of metabolism | Liver (CYP3A4 enzyme) |
| Excretion | Main routes of elimination | Feces and urine |
There is insufficient information on the effects of sildenafil on the breast-fed
- Sildenafil citrate may cause a drop in blood pressure.
- Do not consume large quantities of grapefruit juice while on sildenafil.
- Pregnant or breastfeeding women should not use sildenafil without guidance.
- The drug does not improve libido, only facilitates blood flow.
- It is not intended for recreational use or enhancement.
- Psychological factors can also affect the efficacy of sildenafil.
- Regular medical check-ups are recommended for long-term users.
infant and no information on the effects of sildenafil on milk production. Viagra is a medication used to treat erectile dysfunction by improving blood flow to the penis.
- Sildenafil can enhance the effects of other blood pressure medications.
- The drug’s safety profile is well-studied with many clinical trials.
- Cardiovascular health is an important consideration when taking sildenafil.
- Long-term use requires monitoring for adverse reactions.
- Patient education helps reduce risks and optimize dosage.
- Generic sildenafil offers a cost-effective alternative to branded Viagra.
- Regular health assessments can ensure safe usage.
The drug is available in different dosages.
| Product | Dosage | Quantity + Bonus | Price | |
|---|---|---|---|---|
| Kamagra Soft Tabs | 100mg | 120 + 6 Pills | 311.78€ 296.93€ | |
| Viagra Generic | 100mg | 60 + 4 Pills | 96.36€ 91.77€ | |
| Viagra Generic | 50mg | 360 + 10 Pills | 225.33€ 214.60€ | |
| Viagra Generic | 25mg | 360 + 10 Pills | 213.68€ 203.50€ | |
| Viagra Generic | 200mg | 360 + 10 Pills | 481.98€ 459.03€ | |
| Viagra Generic | 25mg | 180 + 6 Pills | 154.93€ 147.55€ | |
| Viagra Generic | 25mg | 270 + 8 Pills | 184.26€ 175.49€ | |
| Kamagra | 100mg | 84 + 6 Pills | 264.44€ 251.85€ | |
| Kamagra Soft Tabs | 100mg | 32 Pills | 120.11€ 114.39€ | |
| Viagra Generic | 200mg | 60 + 4 Pills | 125.19€ 119.23€ | |
| Kamagra Soft Tabs | 100mg | 60 + 4 Pills | 180.59€ 171.99€ | |
| Viagra Generic | 200mg | 180 + 10 Pills | 277.56€ 264.34€ | |
| Viagra Generic | 50mg | 90 + 6 Pills | 107.37€ 102.26€ | |
| Kamagra | 100mg | 20 Pills | 86.09€ 81.99€ | |
| Viagra Generic | 150mg | 120 + 8 Pills | 177.58€ 169.12€ | |
| Viagra Generic | 50mg | 120 + 6 Pills | 129.64€ 123.47€ |
The appropriate dose depends on factors like age, kidney or liver problems, and other medications being taken.
Administration and Monitoring
In vitro studies suggest zafirlukast inhibits CYP3A (weak) and CYP2C9 (moderate top potent). LiQrev Oral Susp: 1mL, 10mgRevatio/Sildenafil/Sildenafil Citrate Intravenous Inj Sol: 0.8mg, 1mLRevatio/Sildenafil/Sildenafil Citrate Oral Pwd F/Recon: 1mL, 10mgRevatio/Sildenafil/Sildenafil Citrate/Viagra Oral Tab: 20mg, 25mg, 50mg, 100mg 100 mg/day PO for erectile dysfunction; 240 mg/day PO or 30 mg/day IV for pulmonary arterial hypertension. 100 mg/day PO for erectile dysfunction; 240 mg/day PO or 30 mg/day IV for pulmonary arterial hypertension. Weight 45 kg or more: 40 mg PO 3 times daily.Weight 21 to 44 kg: 20 mg PO 3 times daily. Weight 45 kg or more: 40 mg PO 3 times daily.Weight 21 to 44 kg: 20 mg PO 3 times daily.Weight 20 kg or less: 10 mg PO 3 times daily.
Side effects and risks
Guidelines recommend 1 mg/kg/dose PO every 8 hours. Guidelines recommend 1 mg/kg/dose PO every 8 hours and 0.4 mg/kg IV as a loading dose followed by a continuous infusion of 0.067 mg/kg/hour. The physiologic mechanism of erection of the penis involves release of nitric oxide (NO) in the corpus cavernosum during sexual stimulation. Nitric oxide then activates the enzyme guanylate cyclase, which results in increased levels of cGMP. Cyclic guanosine monophosphate causes smooth muscle relaxation in the corpus cavernosum thereby allowing inflow of blood; the exact mechanism by which cGMP stimulates relaxation of smooth muscles has not been determined. While generally considered safe, Viagra can cause side effects, including headaches and low blood pressure.
More about sildenafil
Sildenafil is predominantly metabolized by hepatic cytochrome P450 (CYP) enzymes. 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 sildenafil for women 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).
Sildenafil may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
The metabolite is further metabolized to inactive compounds. 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. It can also interact negatively with other medications like nitrates.
| Brand Name | Manufacturer | Formulation Type | Typical Dosage | Notes |
|---|---|---|---|---|
| Viagra | Pfizer | Tablet | 25, 50, 100 mg | Most well-known brand |
| Revatio | Pfizer | Tablet | 20 mg | For pulmonary hypertension |
| Sildenafil Citrate | Various generic manufacturers | Tablet | 25, 50, 100 mg | Generic versions available |
| Kamagra | Ajanta Pharma | Oral Gel | 100 mg | Used off-label in some countries |
Viagra is a brand-name oral tablet prescribed for erectile dysfunction (ED).
- Sildenafil citrate was first approved by the FDA in 1998.
- Its brand name is Viagra, but generic versions are available.
- The drug is available in tablets of various strengths, typically 25-100 mg.
- It can be prescribed for both men and in specific cases, women.
- Proper dosage varies based on health status and response.
- Use caution in patients with heart problems or low blood pressure.
- It is not a hormone or a testosterone booster.
You’ll find key information about Viagra below.
Potential Side Effects and Safety
Sildenafil can also inhibit PDE5 present in esophageal smooth muscle, lung tissue, and brain tissue. 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).
Administration Notes
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. 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. Drug class: phosphodiesterase type 5 (PDE5) inhibitor In several clinical studies, Viagra was effective in treating erectile dysfunction (ED).
| Storage Condition | Details | Temperature Range | Light Exposure | Humidity |
|---|---|---|---|---|
| Preferred Storage | Cool, dry place | 15-30°C | Keep in original container | Avoid humidity |
| Keep away from light | Protect from direct sunlight | N/A | Yes | N/A |
| Out of reach of children | Safety precaution | N/A | N/A | N/A |
In these studies, males who used the drug had an improved ability to have and keep erections during sexual activity.
Patient Counseling Information
PDE5 is responsible for degradation of cGMP in the corpus cavernosum. 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.
Revatio Injection
Most studies evaluated the efficacy of sildenafil approximately 60 minutes post dose. 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 uk price 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. To learn more about Viagra’s effectiveness, see the “Viagra uses” section.
Pediatric Indications and Dosage
Sildenafil is cleared predominantly by CYP3A (major route) and CYP2C9 (minor route). Use caution and monitor patients for potential sildenafil-related side effects. Verapamil: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with verapamil is necessary; consider a starting dose of 25 mg of sildenafil when prescribed for erectile dysfunction. PDE5 inhibitors, including sildenafil, may potentiate the hypotensive effects of vericiguat. Vigabatrin: (Major) Vigabatrin should not be used with phosphodiesterase inhibitors, which is associated with serious ophthalmic effects (e.g., retinopathy or glaucoma) unless the benefit of treatment clearly outweighs the risks.
Azole Antifungals
Vonoprazan; Amoxicillin; Clarithromycin: (Major) Coadministration of clarithromycin is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). Voriconazole: (Major) Coadministration of voriconazole is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving voriconazole. Voxelotor: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with voxelotor is necessary; consider a starting dose of 25 mg of sildenafil when prescribed for erectile dysfunction. Zafirlukast: (Moderate) Concomitant use of zafirlukast with sildenafil may increase sildenafil exposure.