Sildenafil (Pfizer)

Sildenafil Pfizer is the branded version of sildenafil citrate manufactured by Pfizer, the original developer of the active ingredient marketed under the trade name Viagra.

It is a phosphodiesterase type 5 (PDE5) inhibitor prescribed for the treatment of erectile dysfunction (ED) in adult men.

Sildenafil works by inhibiting the PDE5 enzyme in the corpus cavernosum of the penis.

During sexual stimulation, nitric oxide is released locally, which activates guanylate cyclase and increases levels of cyclic guanosine monophosphate (cGMP).

cGMP relaxes smooth muscle, allowing increased blood flow into the penile erectile tissue. By preventing the breakdown of cGMP, sildenafil prolongs and enhances the erectile response.

Sexual stimulation is required for sildenafil to produce an effect; it does not cause erections in the absence of arousal.

The onset of action is typically 30 to 60 minutes after oral administration, and the effect lasts approximately four to six hours.

Sildenafil Pfizer is available in 25 mg, 50 mg, and 100 mg tablets.

The branded product is identical in quality, safety, and efficacy to generic sildenafil but is preferred by some patients for reasons of familiarity and confidence in the brand.

Take one tablet approximately 30 to 60 minutes before planned sexual activity. Swallow the tablet whole with water.

Sildenafil may be taken with or without food, though a heavy or high-fat meal may delay its onset of action.

Do not take more than one tablet in a 24-hour period. Sexual stimulation is necessary for the medication to work. If no sexual activity occurs, the drug will have no noticeable effect.

Avoid grapefruit juice while taking sildenafil, as it may increase drug levels. Do not combine with nitrate medications or recreational nitrate-containing substances (poppers) under any circumstances.

The recommended starting dose is 50 mg taken approximately one hour before sexual activity. Based on efficacy and tolerability, the dose may be increased to 100 mg or decreased to 25 mg.

Elderly patients (over 65), those with hepatic impairment, and those with severe renal impairment (GFR below 30 mL/min) should start at 25 mg.

Dose adjustment may also be needed when sildenafil is taken with CYP3A4 inhibitors such as erythromycin or ritonavir.

Headache is the most frequently reported side effect, occurring in approximately 10 to 15 per cent of users.

Facial flushing, nasal congestion, dyspepsia, and dizziness each occur in roughly 5 to 10 per cent of men.

Visual disturbances, including a blue-green tinge to vision, increased light sensitivity, and blurred vision, may occur at higher doses.

These effects are transient and resolve after the drug wears off.

Back pain and myalgia are reported occasionally. Priapism (an erection lasting longer than four hours) is rare but constitutes a medical emergency and requires immediate treatment.

Rarely, sudden sensorineural hearing loss and non-arteritic anterior ischaemic optic neuropathy (NAION) have been reported.

The causal relationship is not fully established, but patients should seek immediate medical attention for sudden vision or hearing changes.

Sildenafil must not be taken with nitrate medications (such as glyceryl trinitrate, isosorbide mononitrate, or isosorbide dinitrate) or recreational nitrates (poppers), as the combination can cause a severe and potentially fatal drop in blood pressure.

Use with caution in patients with cardiovascular disease, particularly those in whom sexual activity is inadvisable.

Men who have had a heart attack or stroke within the last six months, or who have unstable angina, uncontrolled arrhythmias, or hypotension, should not use sildenafil.

Inform your prescriber if you have anatomical penile deformities such as Peyronie's disease, or conditions predisposing to priapism, including sickle cell disease or leukaemia.

Sildenafil is contraindicated in patients taking nitrate medications, those with severe cardiovascular conditions where sexual activity is inadvisable, and those with known hypersensitivity to sildenafil or any excipient.

It is contraindicated in patients with recent stroke or myocardial infarction (within six months), severe hepatic impairment, hypotension (blood pressure below 90/50 mmHg), or a known hereditary retinal degenerative disorder such as retinitis pigmentosa.