Description

VIAGRA (sildenafil citrate) is a prescription medication used to treat erectile dysfunction (ED) in men. The search results indicate that there are several options for obtaining VIAGRA or generic sildenafil in Pakistan:

• The NHS in the UK provides information on sildenafil (the generic name for VIAGRA), including how it treats ED and pulmonary hypertension .                                                              Key Benefits

• Treats erectile dysfunction (ED) by improving blood flow to the penis when sexually aroused
• May reduce the progression of ED when taken daily in a low dose
• Improves ability to urinate by relaxing smooth muscle in the prostate
• Improves quality of life, self-esteem, and confidence related to sexual function

Key Ingredient

• Sildenafil citrate is the active ingredient in VIAGRA
• Sildenafil is a phosphodiesterase type 5 (PDE5) inhibitor that relaxes smooth muscle in blood vessels to increase blood flow
  
  

  Sildenafil

  Medication used to treat erectile dysfunction and pulmonary arterial hypertension

  More

  Commonly Known As

  Viagra

  Primary Uses

  Treats erectile dysfunction and pulmonary arterial hypertension; off-label for Raynaud’s phenomenon

  Administration Routes

  Oral (tablets), intravenous therapy, sublingual

  Here is the key information on the mechanism of action of sildenafil (the active ingredient in VIAGRA):

  Mechanism of Action

  The physiological mechanism of erection involves the release of nitric oxide (NO) in the corpus cavernosum during sexual stimulation. This leads to the activation of the enzyme guanylate cyclase, which results in increased levels of cyclic guanosine monophosphate (cGMP). The increased cGMP levels cause smooth muscle relaxation in the corpus cavernosum, allowing increased blood flow and resulting in an erection.Sildenafil enhances the effect of NO by inhibiting phosphodiesterase type 5 (PDE5), the enzyme responsible for the degradation of cGMP in the corpus cavernosum. This inhibition of PDE5 by sildenafil increases the levels of cGMP, leading to smooth muscle relaxation and increased blood flow to the penis, thereby facilitating an erection.Importantly, sildenafil has no direct relaxant effect on isolated corpus cavernosum. Its action depends on the local release of NO. When sexual stimulation causes the local release of NO, the inhibition of PDE5 by sildenafil leads to increased levels of cGMP in the corpus cavernosum, resulting in smooth muscle relaxation and increased blood flow.

  

  

  Chemical Structure of Sildenafil

  The chemical structure of sildenafil is:\ce{C22H30N6O4S}Sildenafil is the active ingredient in the drug VIAGRA. Its chemical name is 1-[[3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-5-yl)-4-ethoxyphenyl]sulfonyl]-4-methylpiperazine citrate.Some key features of the sildenafil structure:

  • It contains a pyrazolopyrimidine core structure
  • It has an ethoxy group and a sulfonyl-methylpiperazine group attached to the core
  • The citrate salt form (sildenafil citrate) is the form used in VIAGRA and other sildenafil products

  

  Key Precautions

  Avoid Nitrates: Do not take VIAGRA if you take nitrate medications, as this combination can cause a dangerous drop in blood pressure.                                                                                  Cardiovascular Conditions: VIAGRA may not be suitable if you have certain cardiovascular conditions, as it can increase the risk of heart attack, stroke, or life-threatening arrhythmias. Discuss your medical history with your doctor.                                                                                             Alpha-Blocker Interactions: VIAGRA should be used with caution if you are also taking alpha-blocker medications, as the combination can cause low blood pressure. You should be stabilized on the alpha-blocker before starting VIAGRA.                                                                                  CYP3A4 Inhibitor Interactions: The dose of VIAGRA should be limited to 25mg when taken with CYP3A4 inhibitors, as these medications can increase the concentration of sildenafil.                 Priapism: Discontinue VIAGRA and seek immediate medical attention if you experience an erection lasting more than 4 hours, as this condition (priapism) can cause permanent damage.                  Vision Changes: Sudden vision loss in one or both eyes has been reported rarely with PDE5 inhibitors like VIAGRA. Discontinue use and seek medical attention if this occurs.                            Hearing Loss: Sudden decrease or loss of hearing has been reported in some patients taking PDE5 inhibitors, including VIAGRA. Discontinue use and seek medical care if this happens.

  Dietary Restrictions

  Avoid High-Fat Meals: Eating a large or high-fat meal before taking VIAGRA can delay the absorption and onset of the medication. It’s best to take VIAGRA on an empty stomach or with a light meal.Limit                                                                                                                                Grapefruit and Grapefruit Juice: Grapefruit and grapefruit juice can inhibit the enzyme CYP3A4, which is responsible for metabolizing sildenafil. This can lead to increased levels of sildenafil in the body and potentially more side effects. Patients should avoid grapefruit products when taking VIAGRA                                                                                                                                      Moderate Alcohol Intake: While VIAGRA can be taken with alcohol, excessive alcohol consumption can increase the risk of side effects like dizziness, headaches, and low blood pressure. Patients should limit alcohol when using VIAGRA.                                                                                        Avoid Nitrate-Containing Foods: Certain foods like nitroglycerin, isosorbide dinitrate, and isosorbide mononitrate are nitrates used to treat chest pain. Taking VIAGRA with these nitrate-containing foods can cause a dangerous drop in blood pressure.

  

  Dosage Information

  • Recommended Dose: The recommended starting dose for most patients is 50 mg, taken approximately 1 hour before sexual activity. The dose can be taken anywhere from 30 minutes to 4 hours before sexual activity.
  • Dosage Adjustments:
    • Maximum Recommended Dose: The maximum recommended dose is 100 mg per day.
    • Dosage Adjustments in Specific Situations:
      • Nitrates: Contraindicated due to the potential for a dangerous drop in blood pressure.
      • Alpha-Blockers: Initiate at 25 mg and stabilize on alpha-blocker therapy before starting VIAGRA.
      • Ritonavir: Recommended dose is 25 mg prior to sexual activity, with a maximum dose of 25 mg within a 48-hour period due to increased blood levels of sildenafil.
      • CYP3A4 Inhibitors: Consider a starting dose of 25 mg due to increased plasma levels of sildenafil.
      • Special Populations: Consider a starting dose of 25 mg for patients > 65 years, patients with hepatic impairment, and patients with severe renal impairment.

  Storage and Handling

  • Storage: Store at 25°C (77°F); excursions permitted to 15-30°C (59-86°F).
  • Handling: Keep all medications away from light and moisture. Do not store in the bathroom.

  Reviews

  • Side Effects: Common side effects include headaches, flushing, indigestion, and vision changes. Rarely, there may be sudden vision loss in one or both eyes or sudden decrease or loss of hearing.
  • Interactions: Drug interactions may change how medications work or increase the risk of serious side effects. Patients should tell their doctor about all the products they use, including prescription drugs, nonprescription drugs, and herbal products.
  • Patient Tips: Adhere to the prescribed dosage and do not alter it without guidance from a healthcare provider. If an overdose is suspected, contact a doctor immediately or seek assistance from poison control or emergency services.

  Additional Information

  • Forms and Strengths: VIAGRA is available in tablet form with strengths of 25 mg, 50 mg, and 100 mg. The tablets are blue, film-coated, and diamond-shaped, with debossed markings indicating the dosage strength.
  • Usage: VIAGRA is used to treat male sexual function problems (impotence or erectile dysfunction) in combination with sexual stimulation. It does not protect against sexually transmitted diseases.

  Use During Pregnancy

  Benefits

  • Pulmonary Arterial Hypertension (PAH): Sildenafil is sometimes used to treat PAH in pregnant women. It can help lower the risk of life-threatening complications associated with untreated PAH during pregnancy.

  Risks

  • General Use: There are no clear risks of taking sildenafil in pregnancy, but it is not recommended for general use in pregnant women unless strictly necessary.
  • Specific Conditions: Sildenafil is contraindicated for use in pregnant women with untreated PAH, as it can lead to heart failure, stroke, preterm delivery, and maternal and fetal death.

  Alternatives

  • No Alternatives: Sildenafil is only prescribed in pregnancy if it is needed for the treatment of PAH. There are no alternatives to sildenafil for this condition.

  Monitoring

  • Pregnancy Monitoring: Women with PAH will be closely monitored during pregnancy to ensure they remain well and that the baby is growing as expected.

  Safety

  • Animal Studies: Animal studies have shown no evidence of embryofetal toxicity or teratogenicity when sildenafil was administered during organogenesis at doses up to 32 and 65 times the recommended human dose.

  Use During Breastfeeding

  Benefits

  • Pulmonary Hypertension: It is safe to take sildenafil for pulmonary hypertension while breastfeeding. The drug only passes into breast milk in tiny amounts and is unlikely to cause any side effects in the baby.

  Risks

  • General Use: There is no clear evidence to suggest that taking sildenafil reduces fertility in either women or men.

  Monitoring

  • Breastfeeding Monitoring: If your doctor or health visitor says your baby is healthy, it is okay to take sildenafil while breastfeeding. However, if you notice any unusual symptoms in your baby, such as poor feeding, sleepiness, paleness, or flushing, you should consult your healthcare provider immediately.

  Safety

  • Breastfeeding Safety: Sildenafil is unlikely to cause any side effects in the baby when taken by the mother while breastfeeding.

  Key Points

  • Pregnancy: Sildenafil is used to treat PAH in pregnant women, but it is not recommended for general use. It is crucial to monitor the mother and fetus closely during pregnancy.
  • Breastfeeding: Sildenafil is safe to take while breastfeeding, as it only passes into breast milk in small amounts and is unlikely to cause harm to the baby.