Patient Experiences with Liquid Sildenafil Therapy

After chronic dosing of 80 mg three times a day sildenafil to patients with systemic hypertension, the mean change from baseline in systolic and diastolic blood pressures was a decrease of 9.4 and 9.1 mmHg, respectively.

Society and culture

Similar effects on blood pressure were noted with 25 mg, 50 mg, and 100 mg doses of sildenafil, therefore the effects are not related to dose or plasma levels within this dosage range. Larger effects were recorded among patients receiving concomitant nitrates [see Contraindications (4)]. Single oral doses of sildenafil up to 100 mg in healthy volunteers produced no clinically relevant effects on electrocardiogram (ECG). After chronic dosing of 80 mg three times a day to patients with PAH, no clinically relevant effects on ECG were reported. After chronic dosing of 80 mg three times a day sildenafil to healthy volunteers, the largest mean change from baseline in supine systolic and supine diastolic blood pressures was a decrease of 9 mmHg and 8.4 mmHg, respectively. After chronic dosing of 80 mg three times a day sildenafil to patients with PAH, lesser reductions than above in systolic and diastolic blood pressures were observed (a decrease in both of 2 mmHg). At single oral doses of 100 mg and 200 mg, transient dose-related impairment of color discrimination (blue/green) was detected using the Farnsworth-Munsell 100-hue test, with peak effects near the time of peak plasma levels.

This finding is consistent with the inhibition of PDE6, which is involved in phototransduction in the retina. An evaluation of visual function at doses up to 200 mg revealed no effects of sildenafil on visual acuity, intraocular pressure, or pupillometry.

References (18)

The safety and efficacy of sildenafil have been established in pediatric patients 1 to 17 years old, for the treatment of PAH (WHO Group I) to improve exercise ability and, in patients too young to perform standard exercising testing, pulmonary hemodynamics thought to underlie improvements in exercise. Use of sildenafil for this indication is supported by evidence from adequate and well-controlled studies in adults with additional PK and safety data in pediatric patients aged 1 year and older [see Adverse Reactions (6.1), Clinical Studies (14)]. The safety and effectiveness of sildenafil have not been established in pediatric patients younger than 1 year of age. During the conduct of the pediatric studies (STARTS-1 and STARTS-2) [see Clinical Studies (14)], an imbalance in the number of deaths was noted: 5/55 (9.1%), 10/74 (13.5%), and 22/100 (22%) in the sildenafil low, medium, and high dose groups, respectively. The causes of death were related to the progression of PAH.

Conflict of interest statement

This safety observation in pediatrics was not confirmed in a study conducted in adults designed to evaluate this risk (Study A1481324). Given the beneficial effects on clinical worsening and death observed in adults with increasing doses (Study A1481324) and the expected similarity of disease in pediatrics and adults, a causal association for the observed dose-related effect on mortality in pediatric patients is unlikely, and therefore, the available data support dosing in pediatric patients > 45 kg up to a maximum of 40 mg three times a day. Clinical studies of sildenafil did not include sufficient numbers of patients aged 65 and over to determine whether they respond differently from younger patients. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy [see Clinical Pharmacology (12.3)]. Sildenafil is rapidly absorbed after oral administration, with a mean absolute bioavailability of 41% (25 to 63%). Maximum observed plasma concentrations are reached within 30 to 120 minutes (median 60 minutes) of oral dosing in the fasted state. When sildenafil is taken with a high-fat meal, the rate of absorption is reduced, with a mean delay in Tmax of 60 minutes and a mean reduction in Cmax of 29%. The mean steady state volume of distribution (Vss) for sildenafil is 105 L, indicating distribution into the tissues.

• Liquid sildenafil citrate is often compounded by pharmacies for personalized doses.
• It is popular among men seeking discreet or fast-acting options.
• The liquid formulation can be used in combination with other therapies.
• Some users report that it provides a more natural sexual experience.
• It may be administered directly into the mouth or mixed with fluids.
• Pricing varies depending on the source and brand of liquid sildenafil.
• Always check the expiration date before using any liquid medication.
• Avoid using expired liquid sildenafil to prevent adverse effects.
• Proper storage extends the medication’s effectiveness.
• Never ingest more than the prescribed dose to prevent toxicity.
• Monitoring for side effects is critical during treatment.

Sildenafil and its major circulating N-desmethyl metabolite are both approximately 96% bound to plasma proteins.

References (33)

Sildenafil is an inhibitor of cGMP specific PDE-5 in the smooth muscle of the pulmonary vasculature, where PDE-5 is responsible for degradation of cGMP. Sildenafil, therefore, increases cGMP within pulmonary vascular smooth muscle cells resulting in relaxation. In patients with PAH, this can lead to vasodilation of the pulmonary vascular bed and, to a lesser degree, vasodilatation in the systemic circulation. Studies in vitro have shown that sildenafil is selective for PDE5. Its effect is more potent on PDE5 than on other known phosphodiesterases (10-fold for PDE6, greater than 80-fold for PDE1, greater than 700-fold for PDE2, PDE3, PDE4, PDE7, PDE8, PDE9, PDE10, and PDE11).

Dig Dis Sci

The approximately 4,000-fold selectivity for PDE-5 versus PDE3 is important because PDE3 is involved in control of cardiac contractility. Sildenafil is only about 10 times as potent for PDE5 compared to PDE6, an enzyme found in the retina and involved in the phototransduction pathway of the retina. This lower selectivity is thought to be the basis for abnormalities related to color vision observed with higher doses or plasma levels [see Clinical Pharmacology (12.2)]. In addition to pulmonary vascular smooth muscle and the corpus cavernosum, PDE5 is also found in other tissues including vascular and visceral smooth muscle and in platelets. The inhibition of PDE5 in these tissues by sildenafil may be the basis for the enhanced platelet anti-aggregatory activity of nitric oxide observed in vitro, and the mild peripheral arterial-venous dilatation in vivo. Protein binding is independent of total drug concentrations. Bioequivalence was established between the 20 mg tablet and the 10 mg/mL oral suspension when administered as a 20 mg single oral dose of sildenafil (as citrate).

• When purchasing liquid sildenafil citrate, confirm the authenticity of the source.
• It is not recommended to buy unregulated or counterfeit versions.
• Homemade or unverified formulations can be unsafe and ineffective.
• Always follow prescribed instructions to ensure safety.
• Regular blood pressure monitoring is advised while using sildenafil.
• Beware of potential allergic reactions, such as rash or swelling.
• Using alcohol with liquid sildenafil can increase side effects.
• Keep track of dosage history for medical reviews.
• Report any adverse effects to a healthcare provider immediately.
• Use of sildenafil citrate does not guarantee sexual performance.
• Consider lifestyle factors like diet and exercise for best results.

Sildenafil is cleared predominantly by the CYP3A (major route) and cytochrome P450 2C9 (CYP2C9, minor route) hepatic microsomal isoenzymes.

4. Contraindications

No dose adjustment for mild to moderate impairment is required. Severe impairment has not been studied [see Clinical Pharmacology (12.3)]. No dose adjustment is required (including severe impairment CLcr < 30 mL/min) [see Clinical Pharmacology (12.3)]. In studies with healthy volunteers of single doses up to 800 mg, adverse events were similar to those seen at lower doses but rates and severities were increased. In cases of overdose, standard supportive measures should be adopted as required.

J Chromatogr B Anal Technol Biomed Life Sci.

Renal dialysis is not expected to accelerate clearance as sildenafil is highly bound to plasma proteins and it is not eliminated in the urine. Sildenafil is also marketed as VIAGRA® for erectile dysfunction. Sildenafil for oral suspension is supplied as white to off-white granular powder containing 1.57 g of sildenafil citrate USP (equivalent to 1.12 g sildenafil) in an amber PET bottle intended for reconstitution. Following reconstitution with 90 mL water, the volume of the oral suspension is 112 mL and the oral suspension contains 10 mg/mL sildenafil. In addition to the bottle, a press-in bottle adapter and an oral dosing syringe (with 1 mL and 2 mL dose markings) are provided. The major circulating metabolite results from N-desmethylation of sildenafil, and is, itself, further metabolized. This metabolite has a phosphodiesterase selectivity profile similar to sildenafil and an in vitro potency for PDE-5 approximately 50% of the parent drug. In healthy volunteers, plasma concentrations of this metabolite are approximately 40% of those seen for sildenafil, so that the metabolite accounts for about 20% of sildenafil’s pharmacologic effects.

Side Effects

Patients on all sildenafil doses achieved a statistically significant reduction in mean pulmonary arterial pressure (mPAP) compared to those on placebo in a study with no background vasodilators [see SUPER-1 in Clinical Studies (14)]. Data on other hemodynamic measures for the sildenafil 20 mg three times a day and placebo dosing regimens is displayed in Table 2. The relationship between these sildenafil pricing effects and improvements in 6-minute walk distance is unknown. Patients on sildenafil medium and high dose groups achieved dose related improvements in pulmonary vascular resistance index (PVRI) and mean pulmonary arterial pressure (mPAP) compared to those on placebo [see STARTS-1 in Clinical Studies (14)]. Improvements were observed with cardiac index in all three sildenafil dose groups over placebo.

Neutrophil-mediated mucosal injury, role of reactive oxygen metabolites

Data on other hemodynamic measures for the sildenafil low, medium and high dose groups compared to placebo is displayed in Table 3. Placebo Corrected Changes in Hemodynamic Parameters by Dose Group Abbreviations: CI = cardiac index; HR = heart rate; mPAP = mean pulmonary arterial pressure; PVRI = pulmonary vascular resistance index; RAP = right atrial pressure; SVRI = systemic vascular resistance index. Note: n = 52, 56, 55, 54, 56, and 56 placebo patients for PVRI, mPAP, CI, SVRI, RAP and HR, respectively. Single oral doses of sildenafil 100 mg administered to healthy volunteers produced decreases in supine blood pressure (mean maximum decrease in systolic/diastolic blood pressure of 8/5 mmHg). The decrease in blood pressure was most notable approximately 1 to 2 hours after dosing and was not different from placebo at 8 hours. In patients with PAH, however, the ratio of the metabolite to sildenafil is higher.

Both sildenafil and the active metabolite have terminal half-lives of about 4 hours. After either oral or intravenous administration, sildenafil is excreted as metabolites predominantly in the feces (approximately 80% of the administered oral dose) and to a lesser extent in the urine (approximately 13% of the administered oral dose).