Sidegra is a medication for treating erectile dysfunction in men. Its active ingredient is Sildenafil citrate, available in 50 mg and 100 mg, manufactured by Thailand’s Government Pharmaceutical Organization (GPO). It belongs to the PDE5 inhibitor class, works within 30–60 minutes, lasts about 4–6 hours, and is a controlled medication that must be prescribed by a doctor.
Many men face erectile dysfunction, yet many still hesitate to see a doctor. Sidegra is one medication that can treat this condition, with clear medical evidence behind it. This article compiles accurate, up-to-date information about Sidegra so readers can understand it before deciding to consult a doctor.
Sidegra is a medication whose active ingredient is Sildenafil citrate, manufactured and distributed by Thailand’s Government Pharmaceutical Organization (GPO). It belongs to the Phosphodiesterase type 5 inhibitor (PDE5 inhibitor) class and is approved by the Thai Food and Drug Administration (FDA) for treating erectile dysfunction (ED) in men.
Sildenafil was first approved by the U.S. FDA back in 1998, and to this day international clinical practice guidelines still classify the PDE5 inhibitor class as first-line therapy for treating ED, as reflected in the Fifth International Consultation on Sexual Medicine (ICSM 2024).
“Most men who come in about ED worry that it’s something shameful, when in fact the condition is treatable — and it is often an early warning sign of vascular disease that deserves further testing. The right first step is a medical assessment before using the medication, not buying pills to try on your own.” — Specialist physician, PSK Clinic
At PSK Clinic, a doctor provides the consultation and prescribes Sidegra, assessing each individual’s suitability and indications case by case.
What Product Information Does Sidegra Have?
Here is a summary table of Sidegra’s product information for an overview before the details.
| Item | Details |
|---|---|
| Brand name | Sidegra® |
| Active ingredient | Sildenafil citrate |
| Manufacturer | Government Pharmaceutical Organization (GPO), Thailand |
| Available strengths | 50 mg and 100 mg (4 tablets per blister pack) |
| Form | Film-coated oral tablet |
| Drug class | PDE5 inhibitor |
| Onset & duration | Starts working in 30–60 minutes, lasts about 4–6 hours |
| Approximate price | THB 250–400 per pack (varies by facility) |
| Drug category | Controlled medication, must be prescribed by a doctor |
The GPO produces Sidegra mainly in 50 mg and 100 mg strengths. If a doctor wants a patient to start at 25 mg, this can be done by splitting a 50 mg tablet in half. Retail prices vary by facility and pharmacy, generally ranging from about THB 250–400 per pack. Note that because Sidegra is a controlled medication, anyone who wishes to use it must first be assessed and receive a prescription from a doctor.
How Does Sidegra Work?
Sidegra works by inhibiting the PDE5 enzyme, allowing cGMP to remain longer in the smooth muscle of the penis. Blood vessels then dilate and blood flow increases when there is sexual stimulation, resulting in a better erection that is easier to maintain. The medication only takes effect when sexual stimulation is also present.
Sildenafil works by inhibiting the Phosphodiesterase type 5 (PDE5) enzyme, which normally breaks down cyclic guanosine monophosphate (cGMP) in the smooth muscle of the Corpus cavernosum — the tissue in the penis.
The physiological process involved is as follows:
- When sexual stimulation occurs, the parasympathetic nerves release Nitric oxide (NO).
- NO stimulates the enzyme Guanylate cyclase, raising the level of cGMP in the smooth muscle.
- cGMP relaxes the smooth muscle, dilating blood vessels so more blood flows into the Corpus cavernosum.
- Sildenafil inhibits PDE5 from breaking down cGMP, prolonging this process and helping the penis become erect and stay erect.
An important point users must understand is that Sildenafil does not produce an erection automatically. The medication works only when there is also sexual stimulation. So if the body receives no nerve signals from sexual stimulation, the medication will not take effect.
What Can Sidegra Treat?
Sidegra is used primarily to treat erectile dysfunction (ED) in men. It also has a secondary indication — pulmonary arterial hypertension (PAH) — which falls outside the scope of most clinics.
Primary indication: Erectile dysfunction (ED) in men
Erectile dysfunction refers to the condition in which a man cannot achieve an erection, or cannot maintain one firmly enough, for satisfactory sexual intercourse.
Sildenafil can effectively treat ED regardless of its cause — whether psychological (Psychogenic ED), vascular (Vasculogenic ED), neurological (Neurogenic ED), or ED associated with diabetes.
Secondary indication: Pulmonary arterial hypertension (PAH)
Besides treating ED, doctors also use Sildenafil at 20 mg three times daily to treat Pulmonary Arterial Hypertension (PAH), which helps patients exercise better and slows disease progression. However, this indication falls outside the scope of PSK Clinic’s services.
How Do You Take Sidegra, and What Dose Is Right?
The standard starting dose of Sidegra is 50 mg, taken once about 1 hour before sexual activity. A doctor may reduce it to 25 mg or increase it to 100 mg depending on the response, and it must not be taken more than once a day.
Recommended dosage for ED
The standard starting dose is 50 mg, taken once about 1 hour before sexual activity.
After that, the doctor may adjust the dose based on the patient’s response and side effects, as follows:
- Reduce to 25 mg (by splitting a 50 mg tablet) if this is sufficient or if side effects occur.
- Increase to 100 mg if 50 mg is not effective enough.
The maximum dose is 100 mg per day, and it should not be taken more than once daily.
Factors that affect the medication's effectiveness
- Timing: The ideal window is 30–60 minutes before sexual activity. The medication lasts about 4–6 hours.
- Food: Taking the medication with or after a high-fat meal slows absorption and lowers the peak blood concentration (Cmax) by about 29%. It is therefore recommended to take it on an empty stomach or after a low-fat meal.
- Sexual stimulation: The medication requires sexual stimulation to work normally.
What Side Effects Does Sidegra Have?
Common side effects of Sidegra include headache, flushing, nasal congestion, and indigestion, which are usually temporary and resolve on their own once the medication wears off. Serious side effects — such as an erection lasting more than 4 hours, or sudden loss of vision or hearing — are very rare but require immediate medical attention.
Common side effects (more than 10%)
The following side effects are usually temporary and resolve on their own once the medication wears off.
- Headache: The most common side effect, caused by blood vessel dilation.
- Flushing: A feeling of warmth or redness over the face, neck, and chest.
- Nasal congestion: Swelling of the nasal lining from the vasodilatory effect.
- Dyspepsia (indigestion): Burning stomach pain or a feeling of fullness.
Less common side effects (1–10%)
- Visual disturbances: Users may temporarily see things tinted blue or green (Cyanopsia/Chromatopsia), have blurred vision, or be unusually sensitive to light. These occur because the medication inhibits the PDE6 enzyme in some retinal photoreceptor cells.
- Dizziness: Caused by a slight drop in blood pressure.
- Palpitations / rapid heartbeat (Tachycardia)
- Muscle pain (Myalgia)
- Skin rash
Serious side effects requiring immediate medical attention
Priapism (abnormally prolonged erection) is a condition in which the penis stays erect for more than 4 hours without sexual stimulation. This is a medical emergency requiring immediate treatment, because if left untreated it can cause permanent damage to penile tissue, leading to permanent ED. Those at high risk include patients with sickle cell disease, leukemia, and multiple myeloma.
Sudden vision loss is a very rare condition caused by reduced blood supply to the optic nerve (Non-arteritic anterior ischemic optic neuropathy, or NAION). Those at higher risk include people with coronary artery disease, diabetes, high blood pressure, and certain retinal characteristics.
Sudden hearing loss is also very rare. It usually occurs immediately or within a few hours of taking the medication. Anyone with these symptoms must see a doctor right away for assessment and treatment.
Who Should Not Use Sidegra?
People who must absolutely not use Sidegra are those taking any type of nitrate medication (including Poppers), those taking Riociguat, and those allergic to Sildenafil — because of the risk of a severe, even fatal, drop in blood pressure. Those with serious heart disease, abnormal blood pressure, or severe liver disease must be assessed by a doctor first.
Absolute contraindications
Do not use with any form of nitrate medication. This is the most important contraindication, because when Sildenafil acts together with nitrates, the two drugs amplify each other’s vasodilatory effect, causing blood pressure to drop severely and potentially become life-threatening.
Nitrate medications to watch out for include:
- Glyceryl trinitrate (GTN, Nitroglycerin) in all forms — sublingual, transdermal patch, injection, and spray
- Isosorbide dinitrate (ISDN)
- Isosorbide mononitrate (ISMN)
- Amyl nitrite and alkyl nitrites (“Poppers”), often used among men who have sex with men (MSM) — absolutely must not be combined
Do not use with Riociguat (Adempas). This medication treats pulmonary hypertension and acts on the cGMP pathway just like Sildenafil. Used together, the patient is at risk of a severe drop in blood pressure.
Do not use in those with a history of allergy to Sildenafil or any component of the medication.
What Does Sidegra Interact With? (Drug Interactions)
Sidegra interacts with several drug classes, especially nitrates (must not be combined), alpha-blockers, and CYP3A4 inhibitors such as HIV antivirals and antifungals, which raise the medication’s blood levels. Users should therefore tell the doctor about all their regular medications before receiving the prescription.
Nitrates: An absolute contraindication. Those using short-acting nitrates must wait at least 24 hours before taking Sildenafil, and at least 48 hours for long-acting forms.
Alpha-blockers: Such as Tamsulosin, Doxazosin, and Terazosin, used to treat an enlarged prostate. This class can amplify the blood-pressure-lowering effect when combined with Sildenafil, so doctors usually recommend starting at 25 mg and taking it at least 4 hours apart from the alpha-blocker.
CYP3A4 inhibitors: This class inhibits the metabolism of Sildenafil, raising its blood levels, so the doctor must reduce the Sildenafil dose. Drugs in this class include:
- Ritonavir (HIV antiviral): Do not use more than 25 mg of Sildenafil within 48 hours.
- Ketoconazole, Itraconazole (antifungals)
- Erythromycin, Clarithromycin (macrolide antibiotics)
- Saquinavir, Indinavir (protease inhibitor antivirals)
CYP3A4 inducers: This class accelerates the metabolism of Sildenafil, lowering its levels, so the doctor may need to increase the dose. Drugs in this class include Rifampicin, Carbamazepine, Phenytoin, and Phenobarbital.
Antihypertensive medications: If Sildenafil is used with several blood-pressure medications, the lowering effects may add up. Users should monitor their blood pressure and watch for dizziness.
Alcohol: Drinking alcohol increases the risk of low blood pressure and dizziness, and also reduces the medication’s effectiveness in treating ED. Users should therefore avoid it or limit the amount.
Grapefruit juice: Grapefruit juice inhibits the CYP3A4 enzyme in the intestine, raising Sildenafil levels in the blood, so users should avoid it.
How to Store Sidegra and Precautions
- Store the medication below 30°C, away from sunlight and humidity.
- Keep the medication out of reach of children.
- Do not share the medication with others, even if they have similar symptoms.
- If you miss a dose, do not take a make-up dose, because this medication is used only as needed, not daily.
Frequently Asked Questions About Sidegra (FAQ)
How is Sidegra different from Viagra?
Sidegra and Viagra share the same active ingredient, Sildenafil citrate, in the same strengths. The only difference is the manufacturer: the Government Pharmaceutical Organization (GPO) of Thailand makes Sidegra as a generic medication, while Pfizer, the original patent holder, makes Viagra. Both deliver comparable clinical results because they are bioequivalent — but Sidegra has the advantage of being more affordable.
How much does Sidegra cost?
Sidegra’s price varies by facility and strength, generally ranging from about THB 250–400 per pack (4 tablets per pack); the 100 mg strength is more expensive than 50 mg. Because Sidegra is a controlled medication, buyers must first be assessed and receive a prescription from a doctor. Avoid buying from unreliable sources due to the risk of counterfeit medication.
Can you take Sidegra every day?
For on-demand ED treatment, doctors usually prescribe 50–100 mg, taken no more than once a day. In some patients, however, the doctor may consider a low dose of Sildenafil (25 mg) taken daily. This decision must always be under a doctor’s care.
How long does Sidegra last?
Sildenafil has a half-life of about 3–5 hours. It generally works well within 1–4 hours after taking it and may still have some effect for up to 6 hours. However, the duration varies from person to person, depending on age, physical condition, and other factors.
What should you do if Sidegra doesn't work?
The first time you use the medication, some users may get a weaker result than expected, so you should give the medication a fair trial — at least 4–8 times — before concluding it doesn’t work. You should also check for factors that may reduce its effectiveness, such as taking it with a high-fat meal, drinking alcohol, or a lack of sexual stimulation. If it still doesn’t work after adjusting these factors, you should consult a doctor to adjust the dose or switch to another PDE5 inhibitor, such as Tadalafil (which lasts 24–36 hours) or Avanafil (which works quickly, within 15–30 minutes).
Can you use Sidegra with Poppers (amyl nitrite)?
Absolutely not. Poppers, or alkyl nitrites, belong to the nitrate class just like sublingual nitrate tablets. Combined with Sidegra, blood pressure drops severely and suddenly, potentially causing shock and death. This contraindication is especially important for men who have sex with men (MSM), among whom Poppers use is fairly common.
Does Sidegra affect fertility?
Studies have found that Sildenafil does not adversely affect sperm quality or male hormones in men with normal fertility.
Conclusion: Sidegra — An Affordable Option, Under a Doctor's Care
Sidegra is a medication for treating erectile dysfunction in men that is backed by clinical evidence, and international clinical practice guidelines place it in the first-line class. Because the Government Pharmaceutical Organization manufactures it, the medication is affordable and a suitable option for many Thai men. However, Sidegra has several important contraindications and drug interactions, so anyone who wishes to use it must always be assessed by a doctor.
At PSK Clinic in Lat Phrao, Bangkok, a doctor assesses erectile dysfunction, takes a history of underlying conditions and current medications, prescribes Sidegra, and provides guidance on using the medication correctly and safely. If you have questions or would like a consultation, you can reach us through the channels below.
PSK Clinic, Lat Phrao, Bangkok
Tel.095-049-4142
LINE: @pskclinic
References
- องค์การเภสัชกรรม (GPO). Sidegra® (Sildenafil Citrate) Product Information.
- Burnett AL, et al. Evolving medical management of erectile dysfunction: recommendations from the Fifth International Consultation on Sexual Medicine (ICSM 2024). Sexual Medicine Reviews. 2025;13(4):513.
- Levine GN, et al. Princeton IV Consensus Guidelines: PDE5 inhibitors and cardiac health. Journal of Sexual Medicine. 2024;21(2):90.
- Dhaliwal A, Gupta M. PDE5 Inhibitors. StatPearls. NIH National Library of Medicine.
- MedlinePlus. Sildenafil Drug Information.
This content is provided for medical information about Sidegra for PSK Clinic patients. Reviewed by a specialist physician. Last updated 13 June 2026. It cannot replace history-taking, physical examination, and diagnosis by a doctor. Those interested in receiving the medication should consult a doctor for an assessment appropriate to their individual health.
