Cialis and Viagra are both pharmaceutical drugs taken to treat male erectile dysfunction.
Cialis was approved by the FDA on 21st November, 2003 as a prescription medicine used to treat erectile dysfunction. The main ingredient of Cialis is tadalafil. This relaxes the muscles of the penis and increases the blood flow into the penis so that a good erection can be gained followed by sexual stimulation. Cialis was developed by a small biotech firm in US, ICOS and was marketed by Eli Lilly. Cialis is an orange colored pill, available in 5mg, 10mg, and 20mg tablets for oral administration and should be taken when sexual intercourse is intended.
Viagra was approved by FDA on 27th March, 1998 as a prescription medicine for pulmonary arterial hypertension. The main ingredient of Viagra is Sildenafil, the generic name for it is Sildenafil citrate, which relaxes the muscles of penis and increases the blood flow into the penis so that a good erection can be gained followed by sexual stimulation. Viagra is the product of the drug manufacturing company, Pfizer. Viagra is a blue, rounded diamond shaped pill available in 25mg, 50mg and 100mg tablets for oral administration in the fasted state and should be taken when sexual intercourse is intended.
Videos explaining the difference
The following three videos, the first two presented by physicians, compare the two ED drugs, offering information about pros and cons, side effects and suitability of each medication.
Viagra vs. Cialis - Chemical Differences
Cialis: Tadalafil has the empirical formula C22H19N3O4 representing a molecular weight of 389.41. The chemical designation is pyrazino[1´,2´:1,6]pyrido[3,4-b]indole-1,4-dione, 6-(1,3-benzodioxol-5-yl)-2,3,6,7,12,12a-hexahydro-2-methyl-, (6R,12aR)-. It is a crystalline solid that is practically insoluble in water and very slightly soluble in ethanol. CIALIS is available as film-coated, almond-shaped tablets for oral administration. Each tablet contains 5, 10, or 20 mg of tadalafil and the following inactive ingredients:
- croscarmellose sodium
- hydroxypropyl cellulose
- iron oxide
- lactose monohydrate
- magnesium stearate
- microcrystalline cellulose
- sodium lauryl sulfate
- titanium dioxide
Viagra: Sildenafil citrate is designated chemically as 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. Sildenafil citrate is a white to off-white crystalline powder with a solubility of 3.5 mg/mL in water and a molecular weight of 666.7. VIAGRA (sildenafil citrate) is formulated as blue, film-coated rounded-diamond-shaped tablets equivalent to 25 mg, 50 mg and 100 mg of sildenafil for oral administration. In addition to the active ingredient, sildenafil citrate, each tablet contains the following inactive ingredients:
- microcrystalline cellulose
- anhydrous dibasic calcium phosphate
- croscarmellose sodium
- magnesium stearate
- titanium dioxide
- FD & C Blue #2 aluminum lake
Differences in conditions that merit prescription
Cialis: Tadalafil is used for the treatment of erectile dysfunction.
Viagra vs. Cialis - Differences in dosage
Cialis: For most individuals, the recommended starting dose of tadalafil is 10 mg per day taken before sexual activity. Depending on the adequacy of the response or side effects, the dose may be increased to 20 mg or decreased to 5 mg a day. The effect of tadalafil may last up to 36 hours. Individuals who are taking medications that increase the blood levels of tadalafil should not exceed a total dose of 10 mg in 72 hours .Tadalafil may be taken with or without food since food does not affect its absorption from the intestine.
Viagra: For most patients, the recommended dose is 50 mg taken, as needed, approximately 1 hour before sexual activity. However, VIAGRA 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.
Cialis is said to stay in the system up to 4 times as long, and thus considered around 4 times as powerful as Viagra. While Viagra stays active for around 12 to 18 hours, Cialis may active for more than 24 hours.
Drug mechanism differences for Cialis and Viagra
Cialis: Erection of the penis is caused by the filling of the penis with blood. Filling occurs because the blood vessels that bring blood to the penis increase in size and deliver more blood to the penis, and, at the same time, the blood vessels that take blood away from the penis decrease in size and remove less blood from the penis. Sexual stimulation that leads to an erection causes the production and release of nitric oxide in the penis. The nitric oxide causes an enzyme, guanylate cyclase, to produce cyclic guanosine monophosphate (cGMP). It is the cGMP that is primarily responsible for increasing and decreasing the size of the blood vessels carrying blood to and from the penis, respectively, and causing the erection. When the cGMP is destroyed by another enzyme, phosphodiesterase-5, the blood vessels return to their normal size, blood leaves the penis, and the erection ends. Tadalafil prevents phosphodiesterase-5 from destroying cGMP so that cGMP stays around longer. The persistence of cGMP leads to a more prolonged engorgement of the penis with blood.
Viagra: Over half of all men with impotence are thought to have some physical (medical) cause. The remainder are believed to have psychogenic causes of impotence. Medical causes of impotence include diabetes and circulatory, neurological or urological conditions. Penile erection is caused by the engorgement of the penis with blood. This engorgement occurs when the blood vessels delivering blood to the penis increase the delivery of blood and the blood vessels carrying blood away from the penis decrease the removal of blood. Under normal conditions, sexual stimulation leads to the production and release of nitric oxide in the penis. Nitric oxide then activates the enzyme, guanylate cyclase, which causes the production of cyclic guanosine monophosphate (cGMP). It is the cGMP that is primarily responsible for the erection by affecting the amount of blood that the blood vessels deliver and remove from the penis. Sildenafil also reduces the pressure in the pulmonary artery in a serious condition called pulmonary arterial hypertension. Sildenafil inhibits an enzyme called phosphodiesterase-5 (PDE5) which destroys the cGMP. Thus, sildenafil prevents the destruction of cGMP and allows cGMP to accumulate and persist longer. The longer cGMP persists, the more prolonged the engorgement of the penis.
Side Effects of Viagra vs. Cialis
Cialis: Generally mild and shortlived,some of the following side effects have been reported:
- Facial Flushing
- Facial flushing
- Upset stomach
Less common side effects are temporary bluish vision or blurred vision, or being sensitive to light. In clinical studies:
- Patients rarely stopped taking Viagra because of side effects
- The frequency of side effects has been shown to decrease over time
Taking Viagra does not make you more dependent upon it to get or maintain an erection.
Do not take these drugs if
- If you have an allergy to Tadalafil or any other part of this medicine.
- Tell healthcare provider if you are allergic to any medicine. Make sure to tell about the allergy and how it affected you. This includes telling about rash; hives; itching; shortness of breath; wheezing; cough; swelling of face, lips, tongue, or throat; or any other symptoms involved.
- If you are taking any of these medicines: Isosorbide dinitrate, isosorbide mononitrate, or nitroglycerin.
- If you use drugs called "poppers" like amyl nitrate and butyl nitrate.
- If you have been told not to have sex by healthcare provider.
- If you have heart disease, talk with a healthcare provider.
- Check medicines with healthcare provider. This medicine may not mix well with other medicines.
- Do not take this medicine with other medicines used to treat change in sexual ability or desire.
- Avoid grapefruit and grapefruit juice.
- Avoid alcohol (includes wine, beer, and liquor).
- To protect against sexually-transmitted diseases, use a condom.
Drug Interactions - Cialis vs. Viagra
Cialis: The breakdown and elimination of tadalafil from the body may be decreased by erythromycin, ketoconazole (Nizoral), itraconazole (Sporanox), indinavir (Crixivan) and ritonavir (Norvir). Therefore, these drugs may increase the levels of tadalafil in the blood. If these drugs are being used at the same time as tadalafil, the dose of tadalafil should be reduced in order to avoid side effects from high levels of tadalafil. Tadalafil exaggerates the increases in heart rate and lowering of blood pressure caused by nitrates, e.g. nitroglycerin, isosorbide dinitrate (Isordil), isosorbide mononitrate (Imdur, Ismo, Monoket), nitroglycerin (Nitro-Dur, Transderm-Nitro) that are used primarily for treating heart pain (angina). In patients who take nitrates for angina, tadalafil could cause heart pain or possibly even a heart attack by exaggerating the increase in heart rate and the lowering of blood pressure. Therefore, tadalafil should not be used with nitrates. Tadalafil also exaggerates the blood pressure lowering effects of some alpha-blocking drugs e.g., terazosin (Hytrin) that primarily are used for treating high blood pressure or enlargement of the prostate. Individuals who take these alpha-blockers should be on a stable dose of the alpha-blocker before tadalafil is started. In such situations, tadalafil should be started at the lowest dose. If the patient is already taking tadalafil, the alpha-blocker should be started at the lowest dose. Tadalafil and alcohol both lower blood pressure. Therefore, combining tadalafil with alcohol may cause excessive drops in blood pressure and cause dizziness, headaches and increased heart rate.
Viagra: Sildenafil increases the effects of the blood pressure lowering medications. It also increases the blood pressure lowering effects of nitrates, e.g. isosorbide dinitrate (Isordil), isosorbide mononitrate (Imdur, Ismo, Monoket), nitroglycerin (Nitro-Dur, Transderm-Nitro) that are used primarily for treating angina. Patients taking nitrates should not receive sildenafil. Cimetidine (Tagamet), erythromycin, ketoconazole (Nizoral), itraconazole (Sporanox) and mibefradil (Posicor) can cause marked increases in the amount of sildenafil in the body. Patients taking these medications should be observed carefully if sildenafil is used. It is expected that rifampin will decrease blood levels of sildenafil and probably reduce its effectiveness.
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