The US Food and Drug Administration (FDA) has banned numerous products claiming to be Eurycoma longifolia that, in fact, contain only analogs of sildenafil. [44][45][46] Sellers of such fake herbals typically sildenafil citrate 100 mg respond by just changing the names of their products. Sildenafil and/or N-desmethylsildenafil, its major active metabolite, may be quantified in plasma, serum, or whole blood to assess pharmacokinetic status in those receiving the drug therapeutically, to confirm the diagnosis in potential poisoning victims, or to assist in the forensic investigation in a case of fatal overdose. Nitric oxide (NO) in the corpus cavernosum of the penis binds to guanylate cyclase receptors, which results in increased levels of cGMP, leading to smooth muscle relaxation (vasodilation) of the intimal cushions of the helicine arteries.
6.2 Postmarketing Experience
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. [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.
Placing an Order
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. [4] Some sildenafil users have complained of seeing everything tinted blue (cyanopsia). [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. Patients thus taking the drug may experience colorvision abnormalities. Some complained of blurriness and loss of peripheral vision. This smooth muscle relaxation leads to vasodilation and increased inflow of blood into the spongy tissue of the penis, causing an erection.
| Product | Dosage | Quantity + Bonus | Price | |
|---|---|---|---|---|
| Viagra Generic | 25mg | 120 + 6 Pills | 125.56€ 119.58€ | |
| Viagra Generic | 150mg | 60 + 4 Pills | 111.25€ 105.95€ | |
| Viagra Generic | 200mg | 10 Pills | 40.96€ 39.01€ | |
| Viagra Generic | 25mg | 30 + 4 Pills | 47.97€ 45.69€ | |
| Kamagra Polo | 100mg | 60 + 4 Pills | 189.39€ 180.37€ | |
| Viagra Generic | 50mg | 60 + 4 Pills | 83.93€ 79.93€ | |
| Kamagra Soft Tabs | 100mg | 180 + 8 Pills | 425.45€ 405.19€ | |
| Kamagra Oral Jelly | 100mg | 21 Sachets | 95.92€ 91.35€ | |
| Viagra Generic | 50mg | 360 + 10 Pills | 225.33€ 214.60€ | |
| Viagra Generic | 200mg | 60 + 4 Pills | 125.19€ 119.23€ | |
| Kamagra Polo | 100mg | 272 + 12 Pills | 622.94€ 593.28€ | |
| Viagra Generic | 25mg | 10 Pills | 25.19€ 23.99€ | |
| Kamagra Soft Tabs | 100mg | 84 + 4 Pills | 233.05€ 221.95€ | |
| Kamagra | 100mg | 360 + 6 Pills | 839.95€ 799.95€ | |
| Kamagra Polo | 100mg | 84 + 4 Pills | 244.49€ 232.85€ | |
| Kamagra Polo | 100mg | 20 Pills | 83.56€ 79.58€ | |
| Viagra Generic | 50mg | 20 Pills | 40.52€ 38.59€ |
[49] Robert F. Furchgott, Ferid Murad, and Louis Ignarro won the Nobel Prize in Physiology or Medicine in 1998 for their independent study of the metabolic pathway of nitric oxide in smooth muscle vasodilation. The molecular mechanism of smooth muscle relaxation involves the enzyme CGMP-dependent protein kinase, also known as PKG. This kinase is activated by cGMP and it phosphorylates multiple targets in the smooth muscle cells, namely myosin light chain phosphatase, RhoA, IP3 receptor, phospholipase C, and others. [50] Overall, this results in a decrease in intracellular calcium and desensitizing proteins to the effects of calcium, engendering smooth muscle relaxation.
6.1 Clinical Trials Experience
The 2007 Ig Nobel Prize in aviation went to Patricia V. Agostino, Santiago A. Plano, and Diego A. Golombek of Universidad Nacional de Quilmes, Argentina, for their discovery that sildenafil helps treat jet lag recovery in hamsters. Professional athletes have been documented using sildenafil, believing the opening of their blood vessels will enrich their muscles.
Limitation of Warranty & Liability
In turn, they believe it will enhance their performances. Acetildenafil and other synthetic structural analogs of sildenafil which are PDE5 inhibitors have been found as adulterants in a number of "herbal" aphrodisiac products sold over-the-counter. [41] These analogs have not undergone any of the rigorous testing that drugs like sildenafil have passed, and thus have unknown side-effect profiles. [42] Some attempts have been made to ban these drugs, but progress has been slow so far, as, even in those jurisdictions that have laws targeting designer drugs, the laws are drafted to ban analogs of illegal drugs of abuse, rather than analogs of prescription medicines. However, at least one court case has resulted in a product being taken off the market. The molecular structure of sildenafil is similar to that of cGMP and acts as a competitive binding agent of PDE5 in the corpus cavernosum, resulting in more cGMP and increased penile response to sexual stimulation.
How to take Viagra Connect Tablets
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. "[25] A careful review of pooled data from clinical trials containing well documented information about the dose and duration of exposure to the drug for a large number of patients, yields no evidence for an increased risk of non-arteritic anterior ischemic optic neuropathy or other adverse ocular events associated with PDE5 inhibitor use. Rare but serious adverse effects found through postmarketing surveillance include prolonged erections, severe low blood pressure, myocardial infarction (heart attack), ventricular arrhythmias, stroke, increased intraocular pressure, and sudden hearing loss. [4] In October 2007, the FDA announced that the labeling for all PDE5 inhibitors, including sildenafil, required a more prominent warning of the potential risk of sudden hearing loss. Care should be exercised by people who are also taking protease inhibitors for the treatment of HIV infection.
Sildenafil may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
Protease inhibitors inhibit the metabolism of sildenafil, effectively multiplying the plasma levels of sildenafil, increasing the incidence and severity of side effects. Those using protease inhibitors are recommended to limit their use of sildenafil to no more than one 25 mg dose every 48 hours. [4] Other drugs that sildenafil pick up interfere with the metabolism of sildenafil include erythromycin and cimetidine, both of which can also lead to prolonged plasma half-life levels. The use of sildenafil and an α1 blocker (typically prescribed for hypertension or for urologic conditions, such as benign prostatic hypertrophy) at the same time may lead to low blood pressure, but this effect does not occur if they are taken at least 4 hours apart. Concomitant use of nitric oxide donors, organic nitrites and nitrates,[30] such as: nitroglycerinisosorbide mononitrateisosorbide dinitratesodium nitroprussidealkyl nitrites (commonly known as "poppers") Concomitant use of soluble guanylyl cyclase stimulators, such as riociguat Sildenafil should not be used if sexual activity is inadvisable due to underlying cardiovascular risk factors. [49][51] Without sexual stimulation, and therefore lack of activation of the NO/cGMP system, sildenafil should not cause an erection. Other drugs that operate by the same mechanism include tadalafil (Cialis) and vardenafil (Levitra).
- Store sildenafil tablets in a cool, dry place away from moisture.
- Keep out of reach of children and pets.
- Do not use expired medication; check expiry date on the pack.
Sildenafil is broken down in the liver by hepatic metabolism using cytochrome p450 enzymes, mainly CYP450 3A4 (major route), but also by CYP2C9 (minor route) hepatic isoenzymes. The major product of metabolisation by these enzymes is N-desmethylated sildenafil, which is metabolised further. This metabolite also has an affinity for the PDE receptors, about 40% of that of sildenafil.
| Ingredient | Quantity per Tablet | Function | Notes |
|---|---|---|---|
| Sildenafil Citrate | 50 mg | Active pharmaceutical ingredient | Main active component |
| Microcrystalline Cellulose | 50 mg | Filler and binder | Ensures tablet cohesion |
| Magnesium Stearate | 1 mg | Lubricant | Facilitates manufacturing |
| Hypromellose | 10 mg | Coating agent | Protects active drug |
| Lactose Monohydrate | 20 mg | Binder | Adds bulk |
| Titanium Dioxide | 2 mg | Opacifier | Gives whitening effect |
Thus, the metabolite is responsible for about 20% of sildenafil's action.
| Country/Region | Approval Status | Regulatory Body | Notes |
|---|---|---|---|
| United States | Approved | FDA | As prescription medication |
| European Union | Approved | EMA | Available as prescribed |
| Canada | Approved | Health Canada | Prescription only |
| Australia | Approved | TGA | Strict prescribing guidelines |
| India | Approved | CDSCO | Widely used, generic versions available |
Sildenafil is excreted as metabolites predominantly in the feces (about 80% of administered oral dose) and to a lesser extent in the urine (around 13% of the administered oral dose).
What should I know about storage and disposal of this medication?
Sildenafil's popularity with young adults has increased over the years. [32] Sildenafil's brand name, Viagra, is widely recognized in popular culture, and the drug's association with treating erectile dysfunction has led to its recreational use. [33] The reasons behind such use include the belief that the drug increases libido, improves sexual performance,[33] or permanently increases penis size. [34] Studies on the effects of sildenafil when used recreationally are limited, but suggest it has little effect when used by those who do not have erectile dysfunction. In one study, a 25 mg dose was shown to cause no significant change in erectile quality, but did reduce the postejaculatory refractory time.
Who is Sildenafil 50mg suitable for?
[35] This study also noted a significant placebo effect in the control group. Unprescribed recreational use of sildenafil and other PDE5 inhibitors is noted as particularly high among users of illegal drugs. [36] Sildenafil is sometimes used to counteract the effects of other substances, often illicit. [33] Some users mix it with methylenedioxymethamphetamine (MDMA, ecstasy), other stimulants, or opiates in an attempt to compensate for the common side effect of erectile dysfunction, a combination known as "sextasy", "rockin' and rollin'", "hammerheading", or "trail mix". [33] Mixing it with amyl nitrite, another vasodilator, is particularly dangerous and potentially fatal. If taken with a high-fat meal, absorption is reduced; the time taken to reach the maximum plasma concentration increases by around one hour, and the maximum concentration itself is decreased by nearly one-third. When taken orally, sildenafil for erectile dysfunction results in an average time to onset of erections of 27 minutes (ranging from 12 to 70 minutes). Sublingual use of sildenafil for erectile dysfunction results in an average onset of action of 15 minutes and lasting for an average of 40 minutes.
| Condition | Details | Rationale |
|---|---|---|
| Temperature | Store at 15-30°C (59-86°F) | Preserves stability |
| Humidity | Keep in a dry place, away from moisture | Prevents degradation |
| Light Exposure | Store in original container, away from light | Protects the active ingredient |
| Shelf Life | Typically 2-3 years from manufacturing date | Ensures efficacy |
| Safety Precautions | Keep out of reach of children | Prevent accidental ingestion |
The preparation steps for synthesis of sildenafil are:[54] Methylation of 3-propylpyrazole-5-carboxylic acid ethyl ester with hot dimethyl sulfate Hydrolysis with aqueous sodium hydroxide (NaOH) to free acid Carboxamide formation with refluxing thionyl chloride/NH4OH Reduction of nitro group to amino group Sildenafil (compound UK-92,480) was synthesized by a group of pharmaceutical chemists led by Simon Campbell[55] working at Pfizer's Sandwich, Kent, research facility in England. It was initially studied for use in hypertension (high blood pressure) and angina pectoris (a symptom of ischaemic heart disease).
- Sildenafil 50mg can be prescribed for pulmonary arterial hypertension.
- The dose varies depending on individual health and doctor recommendations.
- Always follow medical advice for dosage and frequency.