Sildenafil Citrate
Sildenafil Citrate Tablets
Composition
Sildenafil Citrate 100 Tablet
Each film-coated tablet contains
Sildenafil citrate equivalent to
Sildenafil ...................... 100 mg
Sildenafil citrate, an oral therapy for erectile dysfunction, is a selective inhibitor of cyclic guanosine monophosphate (cGMP) - specific phosphodiesterase type 5 (PDE5).
Dosage Form Sildenafil Citrate is available as and 100mg film-coated tablets. Pharmacology Pharmacodynamics Mechanism of Action The physiologic mechanism of erection of the penis involves release of nitric oxide (NO) in the corpus cavernosum during sexual stimulation. NO 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 has no direct relaxant effect on isolated human corpus cavernosum, but enhances the effect of nitric oxide (NO) by inhibiting phosphodiesterase type 5 (PDE5), which is responsible for degradation of cGMP in the corpus cavernosum. When sexual stimulation causes local release of NO, inhibition of PDE5 by sildenafil causes increased levels of cGMP in the corpus cavernosum resulting in smooth muscle relaxation and inflow of blood to the corpus cavernosum. Sildenafil at recommended doses has no effect in the absence of sexual stimulation. In vitro studies have shown that sildenafil is selective for PDE5. Its effect is more potent on PDE5 than on other known phosphodiesterases (10-fold for PDE6, > 80 -fold for PDE1, >700-fold for PDE2, PDE3, PDE4, PDE7, PDE8, PE9, PDE10 and PDE11). The approximately 4,000-fold selectivity for PDE5 versus PDE3 is important because PDE3 is involved in control of cardiac contractility . Sildenafil is only about 10-fold potent for PDE5 compared to PDE6, an enzyme found in the retina; this lower selectivity is thought to be the basis for abnormalities related to colour vision observed with higher doses or plasma levels. Effects of sidenafil on Erectile Response : In eight double-blind, placebo-controlled crossover studies of patients with either organic or psychogenic erectile dysfunction, sexual stimulation resulted in improved erections, as assessed by an objective measurement of hardness and duration of erections (RigiScanR), after sidenafil administration compared with placebo. Effects of sidenafil on Blood Pressure : Single oral doses of sildenafil (100 mg) administered to healthy volunteers produced decreases in supine blood pressure (mean maximum decrease in systolic/diastolic blood pressure of 8.4/5.5 mmHg). The decrease in blood pressure was most notable approximately 1-2 hours after dosing, and was not different than placebo at 8 hours. Larger effects were recorded among patients receiving concomitant nitrates . Effects of sidenafil on Cardiac Parameters : Single oral doses of sildenafil up to 100 mg produced no clinically relevant changes in the ECGs of normal male volunteers. Effects of sidenafil on Vision: At single oral doses of 100 mg and 200 mg, transient dose-related impairment of color discrimination (blue/green) was detected using the Farnsworth-Munsell 100-hue test, with peak effects near the time of peak plasma levels . Pharmacokinetics Absorption and Distribution: Sidenafil is rapidly absorbed. Maximum observed plasma concentrations are reached within 30 to 120 minutes (median 60 minutes) of oral dosing in the fasted state. When sidenafil is taken with a high fat meal, the rate of absorption is reduced, with a mean delay in T max of 60 minutes and a mean reduction in C max of 29%. The mean steady state volume of distribution (Vss) for sildenafil is 105 L, indicating distribution into the tissues. 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. Metabolism and Excretion: Sildenafil is cleared predominantly by the CYP3A4 (major route) and CYP2C9 (minor route) hepatic microsomal isoenzymes. The major circulating metabolite results from N-desmethylation of sildenafil, and is itself further metabolized. 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, so that the metabolite accounts for about 20% of sildenafil's pharmacologic effects. After either oral or intravenous administration, sildenafil is excreted as metabolites predominantly in the feces (approximately 80% of administered oral dose) and to a lesser extent in the urine (approximately 13% of the administered oral dose). Similar values for pharmacokinetic parameters were seen in normal volunteers and in the patient population, using a population pharmacokinetic approach Indications Sildenafil Citrate is indicated for the treatment of erectile dysfunction in men. Dosage And Method of Administration For most patients, the recommended dose is 50 mg taken, as needed approximately 1 hour before sexual activity. However, Sildenafil Citrate may be taken anywhere from 4 hours to 0.5 hour before sexual activity. Based on effectiveness and toleration, the dose may be increased to a maximum recommended dose of 100 mg or decreased to 25 mg. The maximum recommended dosing frequency is once per day. The following factors are associated with increased plasma levels of sildenafil : age > 65 (40% increase in AUC), hepatic impairment (e.g., cirrhosis, 80%), severe renal impairment (creatinine clearance < 30 mL/min, 100%), and concomitant use of potent cytochrome P450 3A4 inhibitors (erythromycin, ketoconazole, itraconazole, ritonavir, saquinavir > 200%). Since higher plasma levels may increase both the efficacy and incidence of adverse events, a starting dose of 25 mg should be considered in these patients. Doses of or 100mg Sildenafil Citrate should not be taken within 4 hours of alpha-blocker administration. Contraindications Use of Sildenafil Citrate is contraindicated in patients with a known hypersensitivity to any component of the tablet. Consistent with its known effects on the nitric oxide/cGMP pathway , sildenafil was shown to potentiate the hypotensive effects of nitrates, and its administration to patients who are concurrently using organic nitrates in any form is therefore contraindicated. Sildenafil is not indicated for use in women and individuals below 18 years of age. Warnings and Precautions Drug Interactions Effects of other drugs on sildenafil In vitro studies : Sildenafil metabolism is principally mediated by the cytochrome P450 (CYP) isoforms 3A4 (major route) and 2C9 (minor route). Therefore, inhibitors of these isoenzymes may reduce sildenafil clearance. In vivo studies : Cimetidine (800 mg), a non-specific CYP inhibitor, caused a 56% increase in plasma sildenafil concentrations when co-administered with sildenafil (50 mg) to healthy volunteers. Stronger CYP3A4 inhibitors such as ketoconazole or itraconazole would be expected to have still greater effects, and population data from patients in clinical trials did indicate a reduction in sildenafil clearance when it was co-administered with CYP3A4 inhibitors (such as ketoconazole, erythromycin, or cimetidine). It can be expected that concomitant administration of CYP3A4 inducers, such as rifampin, will decrease plasma levels of sildenafil. Ritonavir, a highly potent P450 inhibitor, resulted in 300% increase in sildenafil C max and 1000% increase in sildenafil plasma AUC. Single doses of antacid (magnesium hydroxide/aluminium hydroxide) did not affect the bioavailability of sildenafil. Pharmacokinetic data from patients in clinical trials showed no effect on sildenafil pharmacokinetics of CYP2C9 inhibitors (such as tolbutamide, warfarin), CYP2D6 inhibitors (such as selective serotonin reuptake inhibitors, tricyclic antidepressants), thiazide and related diuretics, ACE inhibitors and calcium channel blockers. The AUC of the active metabolite, N-desmethyl sildenafil, was increased 62% by loop and potassium-sparing diuretics and 102% by non-specific beta-blockers. These effects on the metabolite are not expected to be of clinical consequence. Effects of sildenafil on other drugs In vitro studies : Sildenafil is a weak inhibitor of the cytochrome P450 isoforms 1A2, 2C9, 2C19, 2D6, 2E1 and 3A4 (IC 50 > 150 mM). Given sildenafil peak plasma concentrations of approximately 1μM after recommended doses, it is unlikely that sildenafil will alter the clearance of substrates of these isoenzymes. In vivo studies : No significant interactions were shown with tolbutamide (250 mg) or warfarin (40 mg), both of which are metabolized by CYP2C9. Sildenafil (50 mg) did not potentiate the increase in bleeding time caused by aspirin (150 mg). Sildenafil (50 mg) did not potentiate the hypotensive effect of alcohol in healthy volunteers with mean maximum blood alcohol levels of 0.08%. No interaction was seen when sildenafil (100 mg) was co-administered with amlodipine in hypertensive patients. The mean additional reduction on supine blood pressure (systolic, 8 mmHg; diastolic, 7 mmHg) was of a similar magnitude to that seen when sildenafil was administered alone to healthy volunteers. Analysis of the safety database showed no difference in the side effect profile in patients taking sildenafil with and without anti-hypertensive medication. In a study of healthy male volunteers, sildenafil (100 mg) did not affect the steady state pharmacokinetics of the HIV protease inhibitors, saquinavir and ritonavir, both of which are CYP3A4 substrates. General There is no controlled clinical data on the safety or efficacy of sildenafil in the following groups; if prescribed, this should be done with caution. ? Patients who have suffered a myocardial infarction, stroke, or life-threatening arrhythmia within the last 6 months; ? Patients with resting hypotension (BP < 90/50) or hypertension (BP > 170/110); ? Patients with cardiac failure or coronary artery disease causing unstable angina; ? Patients with retinitis pigmentosa (a minority of these patients have genetic disorders of retinal phosphodiesterases). A thorough medical history and physical examination should be undertaken to diagnose erectile dysfunction, determine potential underlying causes, and identify appropriate treatment. There is a degree of cardiac risk associated with sexual activity; therefore, physicians may wish to consider the cardiovascular status of their patients prior to initiating any treatment for erectile dysfunction. Agents for the treatment of erectile dysfunction should be used with caution in patients with anatomical deformation of the penis (such as angulation, cavernosal fibrosis or Peyronie's disease), or in patients who have conditions, which may predispose them to priapism (such as sickle cell anaemia, multiple myeloma, or leukaemia). The safety and efficacy of combinations of sildenafil with other treatments for erectile dysfunction have not been studied. Therefore, the use of such combinations is not recommended. Sildenafil Citrate has no effect on bleeding time when taken alone or with aspirin. In vitro studies with human platelets indicate that sildenafil potentiates the antiaggregatory effect of sodium nitroprusside (a nitric oxide donor). There is no safety information on the administration of sildenafil to patients with bleeding disorders or active peptic ulceration. Therefore, Sildenafil Citrate should be administered with caution to these patients. Simultaneous administration of sidenafil to patients taking alpha-blocker therapy may lead to symptomatic hypotension in some patients. Therefore, sidenafil doses above 25 mg should not be taken within 4 hours of taking an alpha-blocker A minority of patients with the inherited condition, retinitis pigmentosa, have genetic disorders of retinal phosphodiesterases. There is no safety information on the administration of sildenafil to patients with retinitis pigmentosa. Therefore, sildenafil should be administered with caution to these patients. Prolonged erection greater than 4 hours and priapism (painful erections greater than 6 hours in duration) have been reported infrequently since market approval of sildenafil. In the event of an erection that persists longer than 4 hours, the patient should seek immediate medical assistance. If priapism is not treated immediately, penile tissue damage and permanent loss of potency could result. The use of sildenafil offers no protection against sexually transmitted diseases. Counseling of patients about the protective measures necessary to guard against sexually transmitted diseases, including the Human Immunodeficiency Virus (HIV), may be considered. Renal impairment In patients with severe renal impairment a starting dose of 25mg should be considered. Hepatic impairment In patients with hepatic impairment a starting dose of 25mg should be considered Pregnancy Category B There are no adequate and well-controlled studies of sildenafil in pregnant women. Sildenafil is not indicated in women. Lactation Sildenafil is not indicated in nursing mothers. Paediatric Use Sildenafil is not indicated in children. Geriatric Use: Healthy elderly volunteers (65 years or over) had a reduced clearance of sildenafil Since higher plasma levels may increase both the efficacy and incidence of adverse events, a starting dose of 25 mg should be considered . Undesirable Effects The most frequent side effects reported with sildenafil use include headache, flushing, dyspepsia, nasal congestion, abnormal vision (mild and transient, predominantly color tinge to vision, but also increased sensitivity to light or blurred vision), urinary tract infection, diarrhea, dizziness, and rash. Serious cardiovascular, cerebrovascular and vascular events have been reported in temporal association with sildenafil use. It is not possible to determine whether these events are related directly to sildenafil, to sexual activity, to the patient's underlying cardiovascular disease, to a combination of these factors, or to other factors (see Warnings and Precautions, General). Overdose In studies with healthy volunteers of single doses up to 800 mg, adverse events were similar to those seen at lower doses but incidence rates were 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 it is not eliminated in the urine. Storage Store below 30 ° C Packaging Information Sildenafil Citrate 50 Blister pack of 4 tablets Sildenafil Citrate 100 Blister pack of 4 tablets What is Sildenafil Citrate ? Sildenafil Citrate is the brand name for Sildenafil. It's a medicine that helps men with erectile dysfunction (ED) have sexual intercourse again. What is erectile dysfunction? Erectile dysfunction is the inability of the penis to become rigid, or stay rigid long enough to complete the sexual act. How does Sildenafil Citrate work? Sildenafil Citrate dilates the arteries in the penis and thus allows filling of blood into sinusoids (small spaces in the penis). As the penis hardens, the veins are compressed restricting the blood flow out of the penis. This filling of blood into the penile spaces causes erection. How should I take Sildenafil Citrate ? Take one tablet one hour before you plan to have sex. Don't take more than one tablet in 24 hours. The medicine comes in tablets of 25 mg, 50 mg and 100 mg. Most patients can start with 50 mg. Even if you take Sildenafil Citrate , you still need physical and mental stimulation and desire to have an erection. If your first dose of Sildenafil Citrate does not help, call your doctor. Your doctor may want to change your tablet strength. What are the side effects of Sildenafil Citrate ? Sildenafil Citrate has some common side effects: -Headache -Flushing (face and upper body turning red and warm) -Stomach upset -Running nose -Vision changes (things look blue) Headache is the most common side effect. Vision changes are least common. Talk to your doctor if you have any side effects that bother you. Can everyone use Sildenafil Citrate ? You should not use Sildenafil Citrate if you take any of these forms of nitrates: -Isosorbide mononitrate (brand names: Monotrate, Vasotrate, Ismo, Imdur, Angicor) -Isosorbide dinitrate (brand names: Sorbitrate, Isordil) -Sublingual nitroglycerin tablets or spray (Angised, Angispan, GTN spray) -Transdermal nitroglycerin patches or ointments (brand names: Top nitro, Nitroderm TTS, Myovin) Please note that the above is not a comprehensive list and mentions only some commonly used brands. If you are not sure of the medicine you are taking, you should consult your doctor. Can I take Sildenafil Citrate with alcohol? You are advised not to take alcohol before taking Sildenafil Citrate . It may alter the response of the drug. Can I take Sildenafil Citrate after food? Yes, but high fat meal should be avoided before taking Sildenafil Citrate to have better response. How well does Sildenafil Citrate work? Sildenafil Citrate is effective in about 80% of the patients suffering from ED. If you use Sildenafil Citrate and get chest pains, be sure to tell your doctor, how long ago it was that you last took Sildenafil Citrate . This information provides a general overview and may not apply to everyone. Talk to your doctor to find out if this information applies to you and to get more information on this subject.
Generic Name: Sildenafil Citrate Tablets 25 mg, 50 mg, 100 mg (sil-DEN-ah-fill)
Brand Name: Viagra Viagra is used for:
Treating sexual function problems in men, such as impotence or erectile dysfunction, and other conditions as determined by your doctor. Viagra is a phosphodiesterase inhibitor. It works by helping the blood flow into the penis to achieve and maintain an erection. Do NOT use Viagra if:
you are allergic to any ingredient in Viagra
you are taking or using azole antifungals (eg, itraconazole), nitroglycerin (eg, tablet, patch, ointment), nitrates (eg, isosorbide), nitroprusside, or ritonavir
you have or have had heart disease, including heart attack or angina pectoris; a stroke; low blood pressure; or severe liver problems
Contact your doctor or health care provider right away if any of these apply to you. Before using Viagra :
Some medical conditions may interact with Viagra . Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you: if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
if you have allergies to medicines, foods, or other substances
if you have life-threatening irregular heartbeat, uncontrolled high blood pressure, cancer of the blood (eg, leukemia, myeloma), bleeding disorders, or an active stomach ulcer
if you have a deformed penis or conditions that may cause a prolonged erection (eg, sickle cell anemia)
if you have kidney problems, bleeding disorders, active stomach ulcers, eye problems (eg, retina diseases like retinitis pigmentosa), or if you have ever had severe loss of vision
Some MEDICINES MAY INTERACT with Viagra . Tell your health care provider if you are taking any other medicines, especially any of the following: Alpha-blockers (eg, prazosin), azole antifungals (eg, itraconazole), barbiturates (eg, phenobarbital), carbamazepine, delavirdine, H2 antagonists (eg, famotidine), HIV protease inhibitors (eg, indinavir), hydantoins (eg, phenytoin), ketolides (eg, telithromycin), macrolides (eg, erythromycin), mibefradil, nonnucleoside reverse transcriptase inhibitors (eg, efavirenz), rifabutin, rifampin, or ritonavir because side effects of Viagra may be increased
Anticoagulants (eg, warfarin), nitrates (eg, isosorbide ), nitroglycerin (eg, tablet, patch, ointment), or nitroprusside because the risk of side effects such as bleeding or severe low blood pressure may be increased
Bosentan because side effects may be increased by Viagra
This may not be a complete list of all interactions that may occur. Ask your health care provider if Viagra may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine. How to use Viagra :
Use Viagra as directed by your doctor. Check the label on the medicine for exact dosing instructions. Viagra comes with an additional patient leaflet. Read it carefully and reread it each time you get Viagra refilled.
Taking Viagra with a high-fat meal may delay the time of onset of Viagra .
Take Viagra by mouth as needed between 4 hours and 30 minutes before sexual activity (about 1 hour before is most effective).
Do not take Viagra more often than once daily as needed.
If you are taking Viagra in doses greater than 25 mg, do not take an alpha-blocker (eg, doxazosin) within 4 hours of taking Viagra . Taking these medicines at the same time may cause very serious side effects such as severe low blood pressure.
Ask your health care provider any questions you may have about how to use Viagra . Important safety information about Viagra :
Viagra may cause dizziness, blurred vision, fainting, or lightheadedness. Do not drive, operate machinery, or do anything else that could be dangerous until you know how you react to Viagra . Using Viagra alone, with certain other medicines, or with alcohol may lessen your ability to drive or perform other potentially dangerous tasks.
To minimize dizziness or lightheadedness, sit up or stand slowly when rising from a seated or lying position.
Viagra may rarely cause a painful penile erection, which can last for long periods of time and is not related to sexual activity. If not treated immediately, this may lead to permanent erectile dysfunction or impotence (not being able to have or maintain an erection for sexual purposes.
Do not use Viagra if your doctor has advised you to avoid sexual activity because of heart problems.
Viagra does not protect against sexually transmitted diseases, including HIV infection. Use "safe sex" practices such as latex condoms.
Use Viagra with caution in the ELDERLY because they may be more sensitive to its effects.
Viagra is not recommended for use in CHILDREN.
PREGNANCY and BREAST-FEEDING: It is not known if Viagra can cause harm to the developing fetus. If you become pregnant while taking Viagra , discuss with your doctor the benefits and risks of using Viagra during pregnancy. It is unknown if Viagra is excreted in breast milk. If you are or will be breast-feeding while you are using Viagra , check with your doctor or pharmacist to discuss the risks to your baby.
Possible side effects of Viagra :
All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome: Back pain; diarrhea; dizziness; flushing; headache; indigestion; joint pain; lightheadedness; nasal stuffiness; vision changes (eg, blurred vision, sensitivity to light, impaired blue/green color discrimination). Seek medical attention right away if any of these SEVERE side effects occur:
Severe allergic reactions (rash; hives; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); changes in heartbeat; chest pain; fainting; nausea; painful or prolonged erection (lasting more than 4 hours); severe dizziness; sudden decrease or loss of vision in one or both eyes; urinary tract infection. Proper storage of Viagra :
Store Viagra at room temperature at 77 degrees F (25 degrees C). Store away from heat, moisture, and light. Do not store in the bathroom. Brief storage at temperatures between 59 and 86 degrees F (15 and 30 degrees C) is permitted. Keep Viagra out of the reach of children and away from pets. General information:
If you have any questions about Viagra , please talk with your doctor, pharmacist, or other health care provider.
Viagra is to be used only by the patient for whom it is prescribed. Do not share it with other people.
If your symptoms do not improve or if they become worse, check with your doctor.
This information is a summary only. It does not contain all information about Viagra . If you have questions about the medicine you are taking or would like more information, check with your doctor, pharmacist, or other health care provider.
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