Product name: Viagra
Specifications: 100mg/tablet, 4 tablets/box
Appearance: This product is a blue diamond film coat.
Main ingredients: Sildenafil Citrate Tablets
Manufacturer: Pfizer Pharmaceutical Co., Ltd.
Indications: For the treatment of sexual erection dysfunction (ED)

Usage and dosage: For most patients, the recommended dose is 50mg, taken about 1 hour before sexual activity; but can be taken at any time within 0.5 to 4 hours before sexual activity. Based on the efficacy and tolerability, the dose can be increased to 100 mg (maximum recommended dose) or reduced to 25 mg. Take it at most once a day.

Side effects: headache, flushing, indigestion, nasal congestion, and visual abnormalities. Visual abnormalities are mild and transient, mainly manifested as pale vision, enhanced light perception or blurred vision.

Contraindication: Patients who take any dosage form of nitrate drugs, whether regular or intermittent, are contraindications. Patients who are allergic to any ingredient in viagra are prohibited.

Precautions:
1. The interaction of sildenafil-nitrates affecting blood pressure can last from the start of administration to the entire 6-hour observation period. So in any case, taking sildenafil and organic nitrates or providing NO drugs (such as sodium nitroprusside) is contraindicated
2. Use sildenafil with caution in the following patients: anatomical deformities of the penis (such as penile deflection, cavernous fibrosis, Peyronie’s disease), diseases that are prone to cause abnormal penile erections (such as sickle cell anemia, multiple myeloma, leukemia). The safety and effectiveness of other methods of treating erectile dysfunction combined with this product have not been studied and are not recommended for simultaneous use. In the presence of cardiovascular risk factors, there is a risk of non-fatal/fatal cardiac events after sexual activity. If angina, dizziness and other symptoms appear at the beginning of sexual activity, sexual activity must be terminated.
3. If you eat food, especially if it contains fat, it will take 1 hour for Viagra to be absorbed and take effect.
4. After taking the medicine, there must be sexual stimuli such as caressing or hugging to have an erection. If the stimulus is stopped, the erection will subside. The medicinal effect can last up to 4 hours, and there will be no persistent erection without sexual stimulation. Viagra does not enhance libido or sexual function

Pharmacokinetics: Sildenafil is rapidly absorbed after oral administration, with an absolute bioavailability of approximately 40%. Its pharmacokinetic parameters are proportional to the dose within the recommended dose range. Eliminate mainly liver metabolism (cytochrome P450 isoenzyme 3A4 pathway) to produce an active metabolite whose properties are similar to sildenafil, a powerful inhibitor of cytochrome P450 isoenzyme 3A4 (CYP4503A4) ( (Eg erythromycin, ketoconazole, itraconazole) and non-specific inhibitors of cytochrome P450 (CYP450), such as cimetidine and sildenafil, may cause sildenafil plasma levels to rise high. The elimination half-life of sildenafil and its metabolites is about 4 hours. When fasting to 25-100 mg, the maximum plasma concentration (Cmax) is reached within about 1 hour.

Storage: Keep in a sealed, cool and dry place below (86°F).
Validity: 24 months

Treatment recommendation: There is currently an internationally used self-assessment form for erectile dysfunction (IIEF-5 for short). With this tool, patients can easily determine which type of ED they belong to. The patient only needs to fill in the questionnaire according to the 5 questions raised in the questionnaire and give their actual conditions. The evaluation method is to add up the total points of the questionnaire, there are generally four cases:
1. If the score reaches 21 points or more, there is no ED;
2. If the points are between 21-12, there may be mild ED, it is recommended to buy three boxes of Viagra as a course of treatment;
3. If the points are between 11-8, it indicates that there is moderate ED, it is recommended to buy 4 boxes of Viagra as a course of treatment;
4. If the points are between 7-5, it is severe ED, it is recommended to buy eight boxes of Viagra as a course of treatment.
If it is divided according to the erection hardness, it can also be divided into 4 levels:
The first level is enlarged, but it is not hard and cannot be inserted; it is recommended to buy eight boxes of Viagra as a course of treatment.
Second grade, slight erection, but not enough to insert; it is recommended to buy 4 boxes of Viagra as a course of treatment;
Level 3, erection can be inserted but not completely firm; it is recommended to purchase three boxes of Viagra as a course of treatment;
Level 4, fully erect and very strong.

商品名稱】 威而鋼（viagra）
【藥品規格】 100mg/粒,4粒/每盒
【狀 態】 本品爲藍色菱形薄膜衣。
【主要成分】 枸橼酸西地那非片
【生産廠家】 輝瑞制藥有限公司
【適 應 症】 用于治療性功能勃起障礙（ED）。

【用法用量】 對大多數患者，推薦劑量爲50mg，在性活動前約1小時服用；但在性活動前0.5～4小時內的任何時候服用均可。基于藥效和耐受性，劑量可增加至 100mg（最大推薦劑量）或降低至25mg。每日最多服用1次。

【不良反應】 頭痛、潮紅、消化不良、鼻塞及視覺異常等。視覺異常爲輕度和一過性的，主要表現爲視物色淡、光感增強或視物模糊。

【禁 忌】 服用任何劑型硝酸酯類藥物的患者，無論是規律或間斷服用，均爲禁忌症。對威而鋼（viagra）中任何成分過敏的患者禁用。

【注意事項】 1.西地那非-硝酸酯類影響血壓的相互作用，可從給藥開始持續到整個6小時的觀察期內。所以在任何情況下，同時服用西地那非和有機硝酸酯類或提供NO類藥物（如硝普鈉）均屬禁忌
2.以下患者慎用西地那非：陰莖解剖畸形（如陰莖偏曲、海綿體纖維化、Peyronie氏病），易引起陰莖異常勃起的疾病（如鐮狀細胞性貧血、多發性骨髓 瘤、白血病）。其他治療勃起功能障礙的方法與本品合用的安全性和有效性尚未研究，不推薦同時使用。在已有心血管危險因素存在時，用藥後性活動有發生非致命 性/致命性心髒事件的危險。在性活動開始時如出現心絞痛、頭暈等症狀，必須終止性活動。
3.如果吃了食物，尤其是含有脂肪，則服用的威而鋼需1小時才會被吸收而發生藥效。
4.服藥之後必須有愛撫或擁抱等的性刺激才會有勃起反應，如果停止性刺激則勃起會消退。藥效可持續長達4小時，沒有性刺激就不會發生持久性勃起。威而鋼並不會增強性慾或性功能

【藥動力學】 西地那非口服後吸收迅速，絕對生物利用度約40%。其藥代動力學參數在推薦劑量範圍內與劑量成比例。消除以肝髒代謝爲主（細胞色素P450同功酶3A4途徑），生成一有活性的代謝産物，其性質與西地那非近似，細胞色素P450同功酶3A4（CYP4503A4）的強效抑制劑（如紅黴素、酮康唑、伊曲康唑） 以及細胞色素P450（CYP450）的非特異性抑制物如西咪替丁與西地那非合用時，可能會導致西地那非血漿水平升高。西地那非及其代謝産物的消除半衰期 約4小時。空腹狀態給予25～100mg時，約1小時內達最大血漿濃度（Cmax）。

【貯 藏】 密封，陰涼幹燥處在（86華氏）以下保存。
【有 效 期】 24月

【療程推薦】 目前有一種國際通用的勃起功能障礙自我評估表(簡稱IIEF-5)。通過這個工具患者可以簡單的判斷出自己是屬于哪一種ED。患者只需按問卷提出的5個問題給出各自實際情況進行填寫問 卷。評估辦法是將問卷的總積分加起來，一般有四種情況：
1.如果分值達到21分以上，說明沒有ED；
2.若積分在21-12之間，有可能患有輕度ED，建議購買三盒威而鋼作為一個療程；
3.若積分在11-8之間，則提示有中度ED，建議購買4盒威而鋼作為一個療程；
4.如果積分在7-5之間則是重度ED，建議購買八盒威而鋼作為一個療程。
如果按勃起硬度來分的話也可以分為四個等級：
一級，增大，但不硬，不能插入；建議購買八盒威而鋼作為一個療程。
二級，輕微勃起，但不足以插入；建議購買4盒威而鋼作為一個療程；
三級，勃起可插入 但不完全堅挺；建議購買三盒威而鋼作為一個療程；
四級，完全勃起並且非常堅挺。