Cialis and Viagra both treat erectile dysfunction effectively but there are some important differences between the two drugs. Cialis lasts longer than Viagra — for up to 36 hours compared with 8 hours for Viagra. Viagra acts faster and can be effective within 30 minutes of taking the pill, while Cialis can take up to 2 hours.
Cialis was approved by the FDA on 21st November, 2003 as a prescription drug 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 to facilitate an erection. 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.
Viagra was approved by the FDA on 27th March, 1998 as a prescription medicine for pulmonary arterial hypertension. The main ingredient of Viagra is Sildenafil, which — similar to Cialis — relaxes the muscles of penis and increases blood flow into the penis. Viagra is a 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.
|Price||2.5 mg (10 tablets): $62-$80. 5 mg (10): $62-$77. 10 mg (10): $339-$401, 20 mg (10): $339-$401. Prices vary by region, store, and available discounts.||25 mg (10 tablets): $288-$383. 50 mg (10): $288-$360. 100 mg (10): $283-$360. Prices vary by region, store, and available discounts.|
|Selling Point||Lower doses, long half-life, with effects that can last up to 36 hours (earning it a nickname: "The Weekend Pill"). Daily dosage option that means patients do not have to time their sexual activity.||Good track record. Has been around five years longer than Cialis and seven years longer than Levitra.|
|How does it work?||Inhibits an enzyme called phosphodiesterase type 5 (PDE5). This relaxes muscles and increases blood flow, allowing those suffering from erectile dysfunction to experience an erection during sexual stimulation.||Inhibits an enzyme called phosphodiesterase type 5 (PDE5). This relaxes muscles and increases blood flow, allowing those suffering from erectile dysfunction to experience an erection during sexual stimulation.|
|How fast does it work?||Varies by person, but users are recommended to take the pill at least 30 minutes to an hour prior to sex.||Varies by person, but users are recommended to take the pill at least 30 minutes to an hour prior to sex.|
|How does it look?||Cialis tablets are almond-shaped and come in various shades of yellow and yellow-orange. They are engraved with "C" and their dosage amount (e.g., C 5 for 5 mg).||Viagra pills are blue-colored, film-coated, and in the shape of elongated diamonds with rounded corners. "Pfizer" is engraved on one side of the pill and "VGR" and a dosage amount are printed on the other side (e.g., VGR50 for 50 mg).|
|Dosage||Comes in 5, 10, and 20 mg tablets.||Comes in 25, 50, and 100 mg tablets.|
|Consumption instructions||Can be taken with or without food. Users are advised to avoid eating grapefruit and drinking grapefruit juice, as they might alter how the drugs work. Taking the pills with greasy or fatty foods can also alter absorption.||Can be taken with or without food. Users are advised to avoid eating grapefruit and drinking grapefruit juice, as they might alter how the drugs work. Taking the pills with greasy or fatty foods can also alter absorption.|
|Storage instructions||Should be stored at a reasonable room temperature and away from moisture. Recommended room temperature range is between 15 and 30C (59-86F).||Should be stored at a reasonable room temperature and away from moisture. Recommended room temperature range is between 15 and 30C (59-86F).|
|Function||To treat erectile dysfunction, pulmonary heart disease.||To treat erectile dysfunction, pulmonary heart disease.|
|Generic Names||Tadalafil, which is not approved for sale as a generic yet.||Sildenafil citrate, which is not approved for sale as a generic yet.|
|Half Life||18 hours.||4 hours.|
|Side effects||Facial flushing (reddening), headaches. Tadalafil also may cause chest pain, low blood pressure, congestion, dizziness.||Facial flushing, headaches, stomach pain, nasal congestion, nausea, diarrhea, and an inability to differentiate between the colors green and blue.|
|FDA Approval||November 21, 2003.||March 27, 1998.|
|Brand owners||Developed by the biotech firm Icos, which was acquired by Eli Lilly and Company.||Viagra is the product of the drug manufacturing company Pfizer.|
|Named after||Came from twisting the company name Eli Lilly||Vigor or Niagara|
|Excretion||Over 60% of the drug is excreted through feces, and more than 30% is excreted through urine.||Over 80% of the drug is excreted through feces, and more than 13% is excreted through urine.|
Video Explaining the Main Differences
In this video, Dr. Ajay Nehra, professor of urology at Mayo Clinic, explains the differences between Viagra, Cialis, and Levitra.
The key differences, according to Dr. Nehra, are:
- Cialis is longer acting. It is called the "weekend pill" because its effects last for up to 36 hours. Viagra and Levitra are shorter acting; their effect fades in about 4-8 hours.
- Viagra and Levitra are faster-acting; they become effective within 30 minutes of taking the pill. Cialis can take up to 2 hours.
- Viagra and Levitra are prone to food interactions and should be avoided with meals, especially high-fat meals. Cialis does not have any known food interactions.
How Viagra and Cialis Pills Look
Cialis and Viagra are taken orally in tablet form. Users are advised by the manufacturers not to cut pills, but to take them whole. Cialis tablets are almond-shaped and come in various shades of yellow and yellow-orange. They are engraved with C and their dosage amount (e.g., C 5 for 5 mg). Viagra pills are blue-colored, film-coated, and in the shape of elongated diamonds with rounded corners. Pfizer is engraved on one side of the pill and VGR and a dosage amount are printed on the other side (e.g., VGR50 for 50 mg).
Mechanism of Action
Both Viagra and Cialis have a similar mechanism of action; they are PDE5 inhibitor drugs that relax muscles and increase blood flow, thereby helping those suffering from erectile dysfunction.
In the following video, a physician explains how PDE5 inhibitor drugs like Cialis, Viagra, and Levitra work and how they are different:
When it comes to dosage, it is important for patients to discuss their full medical history and concerns with their doctors, as this may affect how much and how often Cialis or Viagra is prescribed.
Most doctors start patients on 5 to 10 mg of Cialis as needed, with instructions to take the drug at least 30 minutes prior to sexual activity. Over time, the dosage may be increased to 20 mg. The maximum dosing frequency for Cialis is 2.5 or 5 mg once a day. This dosing method means patients do not have to time their sexual activity as the drug remains in their system.
With Viagra, patients are usually initially prescribed 50 mg as needed and told to take the drug at least an hour prior to sexual activity. Only one 50 mg dose a day is recommended. Over time, patients may be placed on a maintenance regimen of 25 to 100 mg as needed within 30 minutes to four hours of sexual activity; again, only one of these doses is recommended per day.
Either drug can be taken with or without food. Users are advised to avoid eating grapefruit and drinking grapefruit juice, as they might alter how the drugs work. Taking the pills with greasy or fatty foods can also alter absorption.
Currently, Viagra is much more expensive than Cialis. The main selling point of Cialis, that it is long-lasting and has a one-a-day pill that does not require carefully timed sex, has made the drug popular and led to lower prices. Viagra's cost has actually increased over the years as demand has decreased.
The cost of 30 2.5 mg Cialis tablets ranges from $175 to $220 USD (roughly $6-7 per pill, per day), with prices varying slightly by region, store, and available discounts. Meanwhile, 30 5 mg Cialis tablets fall within the same price range, leading many to purchase Cialis at that dosage and split the pills at home, though this is not recommended by the manufacturer.
Ten 25 mg Viagra tablets cost between $288 and $385 USD (roughly $28-39 per pill), with prices varying slightly, again, by region, store, and available discounts.
Both drugs are currently patented, which makes them more expensive. Cialis' patent will expire in 2017, and Viagra's will expire in 2019. Once the patents expire and the FDA approves the sale of the main ingredient in generic form, cheap generics should quickly become available.
Those allergic to either tadalafil and/or sildenafil cannot take Cialis or Viagra. Likewise, those on medications for heart and blood pressure problems should not take these drugs. In the case of both medications, patients should mention to their doctor any and all of the following medical conditions that are relevant to their personal history:
- Bleeding disorders like hemophilia
- Blood cell disorders, including leukemia, multiple myeloma, and sickle cell anemia
- Chest pain
- Heart disease and other heart problems
- High or low blood pressure
- History of congestive heart failure, a heart attack, or stroke
- Liver or kidney disease
- Physical deformity of the penis
- Previous medical recommendation to abstain from sex
- Retinitis pigmentosa
- Stomach ulcers
With both drugs, patients should be careful about drinking alcohol; taking other medications, including vitamins, over-the-counter drugs, and herbal supplements, simultaneously; and eating grapefruit and drinking grapefruit juice, as doing so may alter the body's absorption of the drug or lead to other negative side effects.
Viagra has more severe, negative reactions with more drugs than Cialis does. The two drugs should not be taken simultaneously, with Levitra, or with other drugs that treat impotence or affect the heart and blood pressure.
Drugs that interact negatively with Cialis include alcohol, alpha-blockers, antacids, antibiotics, antifungal medications, heart and blood pressure medications (e.g., other anti-hypertensives), hepatitis C medications, HIV/AIDS medications, Imatinib, nitrates, seizure medications, St. John's Wort, and tuberculosis medications. To learn more about Cialis drug interactions, see Drugs.com's listing.
Viagra interacts with many of the same drugs that Cialis does: alcohol, antibiotics, antifungal medications, cimetidine, heart and blood pressure medications (e.g., other anti-hypertensives), hepatitis C medications, HIV/AIDS medications, Imatinib, nitrates, seizure medications, St. John's Wort, and tuberculosis medications. See a more extensive listing of Viagra's drug interactions.
The possible side effects of Cialis and Viagra are nearly identical. In clinical trials, headache and heartburn were the two most common side effects for both drugs, but both were much more common in Viagra users. Flushing was also extremely common among Viagra users, but not that common among Cialis users by comparison.
In the case of both drugs, severe reactions are uncommon or rare but are possible. Any symptoms of an allergic or severe negative reaction—difficulty breathing; swelling of the face, mouth, tongue, or throat; and/or rash or hives—deserve immediate, emergency medical attention. Painful and prolonged erections (priapism) that last for four hours or longer require emergency medical attention as well.
Common, Less Serious Side Effects
The following common side effects are those which a sizable minority of Cialis and Viagra users experienced while taking the drugs. They are generally not serious side effects, even if annoying. If any feel particularly severe, they should be treated seriously and with a call to a doctor.
- Cold-like symptoms, such as a cough, sore throat, and/or stuffy nose
- Heartburn and/or indigestion
- Nosebleeds (Viagra)
- Muscle aches in the back, arms, or legs
- Redness or warmth of the face, neck, and/or chest
- Sensitivity to light (Viagra)
- Trouble sleeping or staying asleep (Viagra)
- Upset stomach, nausea, or diarrhea
Serious Side Effects
Patients who experience any of the following side effects should discontinue use of the drug they have been prescribed and immediately call their doctor.
- Chest pain and/or a heavy pain that travels through the arm or shoulder and leads to feelings of nausea and general illness
- Irregular heartbeat
- Lightheadedness and feeling faint
- Painful urination (Viagra)
- Seizures or convulsions
- Shortness of breath
- Sudden hearing loss, tinnitus ("ringing" in the ears), or changes in hearing capabilities
- Sudden and severe vision loss or changes in vision
- Swelling in the extremities, such as the hands, ankles, or feet
Storage and Shelf Life
Both drugs should be stored at a reasonable room temperature and away from moisture. Recommended room temperature range is between 15 and 30C (59-86F). Cialis has a shelf life of three years, while Viagra has a shelf life of five years.
The recreational use of both drugs, but most especially of Viagra, is common, likely due to the mistaken belief that the pills affect libido, penis size, or sexual performance. Taking either drug as a healthy individual is unlikely to result in any noticeable effects.
There are cases of Cialis and Viagra being used by those already taking illegal drugs as a means of counteracting those drugs' side effects, some of which may include erectile dysfunction. This can be extremely dangerous and potentially fatal, especially in the case of mixing PDE5 inhibitors like Cialis and Viagra with drugs that have amyl nitrates in them.