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I take 25mg on an empty stomach with a tall glass of water at 8:00AM. It takes effect in 15 minutes on the average and out love-making session goes for over an hour every time. – Age 65, Florida
I decided to try a 25mg Viagra pill. I could feel my penis get erect within 15 minutes, getting harder than usual and lasting longer too – YT, Age 45, Nigeria
A full 100 mg. will give you a Ginsu carving knife that, if put to ultimate use, will render her suitable for burial in a Y-shaped coffin. For most of us, 50 mg. is plenty, ensuring that you can return to a deflated state between orgasms, if so desired. But you may have to picture your grandmother naked, to do so.
The effects last 3 or 4 hours, and it takes 30 to 45 minutes to kick in. 25 or 50 mg tabs work the same for me, no difference. Go for it. – Art, Age 62, Texas
I bought a pill cutter at the grocery store and cut a 50 mg pill in half. It worked faster than a 1/2 hour and I had the first complete sexual experience in over 6 YEARS! William, Age 42, Texas
25mg is best for me and I have found that Viagra makes me a super stud and the girl rides me and always has an orgasm or two. – Pablo, 42, Texas
I find that 25 mg two hours prior to sex is best for me, and allows sensitivity, to remain at its peak. When trying 50 or 100,mg, it took away much of the feeling, and you need stimulation to maintain erection. More is definitely not better, in my case. – Phil, Age 60, California
25mg begins to work in about 15 minutes to a half an hour and lasts for 3 hours or so, Able to have an erection and intercourse more than once in a few hours. – Age 65, New York City
My doctor prescribed 50 mg Viagra. Wow. Instant hard on that lasts for a long time. I take 50 mg about three times a week.
I have tried 100mg from time to time but actually seem to do better with the smaller doses. – JR, Age 65
You have to experiment with the dosage and time lag. I started with 50 mg (good to rev my engine, I think) but ultimately found that 25 mg about 90 minutes before sex is ideal for me. Lower dosage means less nasal congestion and more feeling during sex. But 25 mg still leaves me rock hard and able to hold off climaxing just about as long as I want.
I have experimented with dosage and now find that 25 mg about one half hour before sex is perfect for me. I’m rock hard and can go forever.
I have the pharmacist split a 100 mg pill in four for me so I take 25 mg at a time. When I want to go all night I take the full 100 mg.
I cut a 50 mg in half and find that to be enough.
We came at the same time, and boy did I cum. What force! What makes this whole experience ever better is that I only used half of a 50 mg pill.
I started off with 25 mg, and have reduced it down to 12.5 mg (roughly – I split the 100 mg pill to 8) and find that with this reduced dose, I can still have a rock hard erection as well as a greatly reduced headache.
I have since realized I only need 25mg to keep and maintain an erection. But originally, that night, I took 50mg. – Bill, Chicago, Age 42
GENERIC NAME(S): SILDENAFIL CITRATE
Sildenafil is used to treat high blood pressure in the lungs (pulmonary hypertension ). It works by relaxing and widening the blood vessels in your lungs which allows the blood to flow more easily. Decreasing high blood pressure in the lungs allows your heart and lungs to work better and improves your ability to exercise .
This medication is not recommended for use in children. Discuss the risks and benefits of this medication with the doctor.
OTHER USES: This section contains uses of this drug that are not listed in the approved professional labeling for the drug but that may be prescribed by your health care professional. Use this drug for a condition that is listed in this section only if it has been so prescribed by your health care professional.
Sildenafil is also available in other brands and other strengths to treat erectile dysfunction -ED in men. Do not take this medication with any other product that contains sildenafil or other similar medications for erectile dysfunction -ED or pulmonary hypertension (such as tadalafil, vardenafil).
How to use Viagra
Read the Patient Information Leaflet provided by your pharmacist before you start taking sildenafil and each time you get a refill. If you have any questions, ask your doctor or pharmacist.
To treat high blood pressure in the lungs, take this medication by mouth as directed by your doctor, with or without food, usually 3 times a day (about 4-6 hours apart). Do not increase your dose or take this drug more often than prescribed.
Take this medication regularly to get the most benefit from it. To help you remember, take it at the same times each day.
Tell your doctor if your condition does not improve or if it worsens.
Dizziness. lightheadedness, headache. flushing, stomach upset, nosebleeds. trouble sleeping. or swollen hands/ankles /feet (edema ) may occur. Vision changes such as increased sensitivity to light, blurred vision. or trouble telling blue and green colors apart may also occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.
To reduce the risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position.
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Rarely, sudden decreased vision. including permanent blindness, in one or both eyes (NAION) may occur. If this serious problem occurs, stop taking sildenafil and get medical help right away. You have a slightly greater chance of developing NAION if you have heart disease. diabetes. high cholesterol. certain other eye problems (“crowded disk”), high blood pressure. if you are over 50, or if you smoke.
Rarely, a sudden decrease or loss of hearing, sometimes with ringing in the ears and dizziness, may occur. Stop taking sildenafil and get medical help right away if these effects occur.
Rarely, males may have a painful or prolonged erection lasting 4 or more hours. If this occurs, stop using this drug and get medical help right away, or permanent problems could occur.
Get medical help right away if you have any very serious side effects, including: increased shortness of breath or trouble breathing. fainting .
A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction. including: rash. itching /swelling (especially of the face/tongue /throat), severe dizziness, trouble breathing.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.
In Canada – Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.
Before taking sildenafil, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.
Before using this medication, tell your doctor or pharmacist your medical history, especially of: heart problems (such as heart attack or life-threatening irregular heartbeat in the past 6 months, chest pain/angina, heart failure ), stroke in the past 6 months, high or low blood pressure. a severe loss of body water (dehydration), penis conditions (such as angulation, fibrosis/scarring, Peyronie’s disease ), history of painful/prolonged erection (priapism), conditions that may increase the risk of priapism (such as sickle cell anemia. leukemia, multiple myeloma ), eye problems (such as retinitis pigmentosa. sudden decreased vision, NAION), other lung conditions (such as pulmonary veno-occlusive disease).
This drug may make you dizzy or cause vision problems. Do not drive, use machinery, or do any activity that requires alertness or clear vision until you are sure you can perform such activities safely. Limit alcoholic beverages.
Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).
During pregnancy, sildenafil should be used only when clearly needed. Discuss the risks and benefits with your doctor.
It is unknown if this medication passes into breast milk. Consult your doctor before breast-feeding.
Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor’s approval.
A product that may interact with this drug is: riociguat.
Sildenafil can cause a serious drop in your blood pressure when used with nitrates. A serious drop in blood pressure can lead to dizziness, fainting, and rarely heart attack or stroke. Do not use sildenafil with any of the following: certain drugs used to treat chest pain/angina (nitrates such as nitroglycerin, isosorbide), recreational drugs called “poppers” containing amyl nitrate, amyl nitrite, or butyl nitrite.
If you are also taking an alpha blocker medication (such as doxazosin, tamsulosin) to treat an enlarged prostate/BPH or high blood pressure, your blood pressure may get too low which can lead to dizziness or fainting. Your doctor may adjust your medications to minimize your risk of low blood pressure.
Other medications can affect the removal of sildenafil from your body, which may affect how sildenafil works. Examples include azole antifungals (such as itraconazole, ketoconazole), macrolide antibiotics (such as clarithromycin, erythromycin), HIV protease inhibitors (such as ritonavir, saquinavir), hepatitis C virus protease inhibitors (such as boceprevir, telaprevir), cobicistat, mifepristone, rifampin, among others.
Do not take this medication with any other product that contains sildenafil or other similar medications for erectile dysfunction-ED or pulmonary hypertension (such as tadalafil, vardenafil).
If overdose is suspected, contact a poison control center or emergency room right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include severe dizziness, fainting, painful/prolonged erection.
Do not share this medication with others.
Medical tests (such as eye exams, blood pressure) may be performed periodically to monitor your progress or check for side effects.
If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up.
Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.
Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.
Information last revised October 2015. Copyright(c) 2015 First Databank, Inc.
* Reported during post-marketing surveillance only
**Visual colour distortions: Chloropsia, Chromatopsia, Cyanopsia, Erythropsia and Xanthopsia
***Lacrimation disorders: Dry eye, Lacrimal disorder and Lacrimation increased
Reporting of suspected adverse reactions
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product.
Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme at www.mhra.gov.uk/yellowcard
Healthcare professionals are asked to report any suspected adverse reactions via HPRA Pharmacovigilance, Earlsfort Terrace, IRL – Dublin 2; Tel: +353 1 6764971; Fax: +353 1 6762517. Website: www.hpra.ie ; E-mail: email@example.com .
In single dose volunteer studies of doses up to 800 mg, adverse reactions were similar to those seen at lower doses, but the incidence rates and severities were increased. Doses of 200 mg did not result in increased efficacy but the incidence of adverse reactions (headache, flushing, dizziness, dyspepsia, nasal congestion, altered vision) was increased.
In cases of overdose, standard supportive measures should be adopted as required. Renal dialysis is not expected to accelerate clearance as sildenafil is highly bound to plasma proteins and not eliminated in the urine.
5. Pharmacological properties
5.1 Pharmacodynamic properties
Pharmacotherapeutic group: Urologicals; Drugs used in erectile dysfunction. ATC Code: G04B E03.
Mechanism of action
Sildenafil is an oral therapy for erectile dysfunction. In the natural setting, i.e. with sexual stimulation, it restores impaired erectile function by increasing blood flow to the penis.
The physiological mechanism responsible for erection of the penis involves the 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 cyclic guanosine monophosphate (cGMP), producing smooth muscle relaxation in the corpus cavernosum and allowing inflow of blood.
Sildenafil is a potent and selective inhibitor of cGMP specific phosphodiesterase type 5 (PDE5) in the corpus cavernosum, where PDE5 is responsible for degradation of cGMP. Sildenafil has a peripheral site of action on erections. Sildenafil has no direct relaxant effect on isolated human corpus cavernosum but potently enhances the relaxant effect of NO on this tissue. When the NO/cGMP pathway is activated, as occurs with sexual stimulation, inhibition of PDE5 by sildenafil results in increased corpus cavernosum levels of cGMP. Therefore sexual stimulation is required in order for sildenafil to produce its intended beneficial pharmacological effects.
Studies in vitro have shown that sildenafil is selective for PDE5, which is involved in the erection process. Its effect is more potent on PDE5 than on other known phosphodiesterases. There is a 10-fold selectivity over PDE6 which is involved in the phototransduction pathway in the retina. At maximum recommended doses, there is an 80-fold selectivity over PDE1, and over 700-fold over PDE 2, 3, 4, 7, 8, 9, 10 and 11. In particular, sildenafil has greater than 4,000-fold selectivity for PDE5 over PDE3, the cAMP-specific phosphodiesterase isoform involved in the control of cardiac contractility.
Clinical efficacy and safety
Two clinical studies were specifically designed to assess the time window after dosing during which sildenafil could produce an erection in response to sexual stimulation. In a penile plethysmography (RigiScan) study of fasted patients, the median time to onset for those who obtained erections of 60% rigidity (sufficient for sexual intercourse) was 25 minutes (range 12-37 minutes) on sildenafil. In a separate RigiScan study, sildenafil was still able to produce an erection in response to sexual stimulation 4-5 hours post-dose.
Sildenafil causes mild and transient decreases in blood pressure which, in the majority of cases, do not translate into clinical effects. The mean maximum decreases in supine systolic blood pressure following 100 mg oral dosing of sildenafil was 8.4 mmHg. The corresponding change in supine diastolic blood pressure was 5.5 mmHg. These decreases in blood pressure are consistent with the vasodilatory effects of sildenafil, probably due to increased cGMP levels in vascular smooth muscle. Single oral doses of sildenafil up to 100 mg in healthy volunteers produced no clinically relevant effects on ECG.
In a study of the hemodynamic effects of a single oral 100 mg dose of sildenafil in 14 patients with severe coronary artery disease (CAD) (>70% stenosis of at least one coronary artery), the mean resting systolic and diastolic blood pressures decreased by 7% and 6% respectively compared to baseline. Mean pulmonary systolic blood pressure decreased by 9%. Sildenafil showed no effect on cardiac output, and did not impair blood flow through the stenosed coronary arteries.
A double-blind, placebo-controlled exercise stress trial evaluated 144 patients with erectile dysfunction and chronic stable angina who regularly received anti-anginal medicinal products (except nitrates). The results demonstrated no clinically relevant differences between sildenafil and placebo in time to limiting angina.
Mild and transient differences in colour discrimination (blue/green) were detected in some subjects using the Farnsworth-Munsell 100 hue test at 1 hour following a 100 mg dose, with no effects evident after 2 hours post-dose. The postulated mechanism for this change in colour discrimination is related to inhibition of PDE6, which is involved in the phototransduction cascade of the retina. Sildenafil has no effect on visual acuity or contrast sensitivity. In a small size placebo-controlled study of patients with documented early age-related macular degeneration (n=9), sildenafil (single dose, 100 mg) demonstrated no significant changes in the visual tests conducted (visual acuity, Amsler grid, colour discrimination simulated traffic light, Humphrey perimeter and photostress).
There was no effect on sperm motility or morphology after single 100 mg oral doses of sildenafil in healthy volunteers (see section 4.6).
Further information on clinical trials
In clinical trials sildenafil was administered to more than 8000 patients aged 19-87. The following patient groups were represented: elderly (19.9%), patients with hypertension (30.9%), diabetes mellitus (20.3%), ischaemic heart disease (5.8%), hyperlipidaemia (19.8%), spinal cord injury (0.6%), depression (5.2%), transurethral resection of the prostate (3.7%), radical prostatectomy (3.3%). The following groups were not well represented or excluded from clinical trials: patients with pelvic surgery, patients post-radiotherapy, patients with severe renal or hepatic impairment and patients with certain cardiovascular conditions (see section 4.3).
In fixed dose studies, the proportions of patients reporting that treatment improved their erections were 62% (25 mg), 74% (50 mg) and 82% (100 mg) compared to 25% on placebo. In controlled clinical trials, the discontinuation rate due to sildenafil was low and similar to placebo.
Across all trials, the proportion of patients reporting improvement on sildenafil were as follows: psychogenic erectile dysfunction (84%), mixed erectile dysfunction (77%), organic erectile dysfunction (68%), elderly (67%), diabetes mellitus (59%), ischaemic heart disease (69%), hypertension (68%), TURP (61%), radical prostatectomy (43%), spinal cord injury (83%), depression (75%). The safety and efficacy of sildenafil was maintained in long term studies.
The European Medicines Agency has waived the obligation to submit the results of studies with VIAGRA in all subsets of the paediatric population for the treatment of erectile dysfunction. See section 4.2 for information on paediatric use.
5.2 Pharmacokinetic properties
Sildenafil is rapidly absorbed. Maximum observed plasma concentrations are reached within 30 to 120 minutes (median 60 minutes) of oral dosing in the fasted state. The mean absolute oral bioavailability is 41% (range 25-63%). After oral dosing of sildenafil AUC and Cmax increase in proportion with dose over the recommended dose range (25-100 mg).
When sildenafil is taken with food, the rate of absorption is reduced with a mean delay in tmax of 60 minutes and a mean reduction in Cmax of 29%.
The mean steady state volume of distribution (Vd ) for sildenafil is 105 l, indicating distribution into the tissues. After a single oral dose of 100 mg, the mean maximum total plasma concentration of sildenafil is approximately 440 ng/mL (CV 40%). Since sildenafil (and its major circulating N-desmethyl metabolite) is 96% bound to plasma proteins, this results in the mean maximum free plasma concentration for sildenafil of 18 ng/mL (38 nM). Protein binding is independent of total drug concentrations.
In healthy volunteers receiving sildenafil (100 mg single dose), less than 0.0002% (average 188 ng) of the administered dose was present in ejaculate 90 minutes after dosing.
Sildenafil is cleared predominantly by the CYP3A4 (major route) and CYP2C9 (minor route) hepatic microsomal isoenzymes. The major circulating metabolite results from N-demethylation of sildenafil. This metabolite has a phosphodiesterase selectivity profile similar to sildenafil and an in vitro potency for PDE5 approximately 50% that of the parent drug. Plasma concentrations of this metabolite are approximately 40% of those seen for sildenafil. The N-desmethyl metabolite is further metabolised, with a terminal half life of approximately 4 h.
The total body clearance of sildenafil is 41 L/h with a resultant terminal phase half life of 3-5 h. After either oral or intravenous administration, sildenafil is excreted as metabolites predominantly in the faeces (approximately 80% of administered oral dose) and to a lesser extent in the urine (approximately 13% of administered oral dose).
Pharmacokinetics in special patient groups
Healthy elderly volunteers (65 years or over) had a reduced clearance of sildenafil, resulting in approximately 90% higher plasma concentrations of sildenafil and the active N-desmethyl metabolite compared to those seen in healthy younger volunteers (18-45 years). Due to age-differences in plasma protein binding, the corresponding increase in free sildenafil plasma concentration was approximately 40%.
In volunteers with mild to moderate renal impairment (creatinine clearance = 30-80 mL/min), the pharmacokinetics of sildenafil were not altered after receiving a 50 mg single oral dose. The mean AUC and Cmax of the N-desmethyl metabolite increased up to 126% and up to 73% respectively, compared to age-matched volunteers with no renal impairment. However, due to high inter-subject variability, these differences were not statistically significant. In volunteers with severe renal impairment (creatinine clearance < 30 mL/min), sildenafil clearance was reduced, resulting in mean increases in AUC and Cmax of 100% and 88% respectively compared to age-matched volunteers with no renal impairment. In addition, N-desmethyl metabolite AUC and Cmax values were significantly increased by 200% and 79% respectively.
In volunteers with mild to moderate hepatic cirrhosis (Child-Pugh A and B) sildenafil clearance was reduced, resulting in increases in AUC (84%) and Cmax (47%) compared to age-matched volunteers with no hepatic impairment. The pharmacokinetics of sildenafil in patients with severely impaired hepatic function have not been studied.
5.3 Preclinical safety data
Non-clinical data revealed no special hazard for humans based on conventional studies of safety pharmacology, repeated dose toxicity, genotoxicity, carcinogenic potential, and toxicity to reproduction and development.
6. Pharmaceutical particulars