Sildenafil citrate and blood-pressure-lowering drugs: results of drug interaction studies with an organic nitrate and a calcium antagonist

Its effect is more potent on PDE-5 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).

Proper Use

Concomitant use of sildenafil citrate with nitrates in any form is contraindicated. Concomitant use of sildenafil citrate with ritonavir and other potent CYP3A inhibitors is not recommended. In drug-drug interaction studies, sildenafil (25 mg, 50 mg, or 100 mg) and the alpha-blocker doxazosin (4 mg or 8 mg) were administered simultaneously to patients with benign prostatic hyperplasia (BPH) stabilized on doxazosin therapy. In these study populations, mean additional reductions of supine systolic and diastolic blood pressure of 7/7 mmHg, 9/5 mmHg, and 8/4 mmHg, respectively, were observed. Mean additional reductions of standing blood pressure of 6/6 mmHg, 11/4 mmHg, and 4/5 mmHg, respectively, were also observed.

Multimedia: Slideshows, Images & Quizzes

There were infrequent reports of patients who experienced symptomatic postural hypotension. These reports included dizziness and light-headedness, but not syncope. When sildenafil 100 mg liquid sildenafil citrate oral was co-administered with amlodipine, 5 mg or 10 mg oral, to hypertensive patients, the mean additional reduction on supine blood pressure was 8 mmHg systolic and 7 mmHg diastolic. There are no adequate and well-controlled studies of sildenafil in pregnant women. No evidence of teratogenicity, embryotoxicity, or fetotoxicity was observed in pregnant rats or rabbits dosed with sildenafil 200 mg/kg/day during organogenesis, a level that is, on a mg/m2 basis, 32- and 68-times, respectively, the recommended human dose (RHD) of 20 mg three times a day. The approximately 4,000-fold selectivity for PDE-5 versus PDE3 is important because PDE3 is involved in control of cardiac contractility.

Product	Dosage	Quantity + Bonus	Price
Kamagra	100mg	180 + 6 Pills	436.79€ 415.99€	Buy
Viagra Generic	200mg	360 + 10 Pills	481.98€ 459.03€	Buy
Viagra Generic	100mg	360 + 10 Pills	330.21€ 314.49€	Buy
Kamagra Soft Tabs	100mg	60 + 4 Pills	180.59€ 171.99€	Buy
Kamagra Soft Tabs	100mg	272 + 12 Pills	593.42€ 565.16€	Buy
Kamagra Polo	100mg	180 + 8 Pills	446.52€ 425.26€	Buy
Viagra Generic	200mg	60 + 4 Pills	125.19€ 119.23€	Buy
Kamagra Polo	100mg	60 + 4 Pills	189.39€ 180.37€	Buy
Kamagra Oral Jelly	100mg	30 + 5 Sachets	136.20€ 129.71€	Buy
Viagra Generic	25mg	10 Pills	25.19€ 23.99€	Buy
Viagra Generic	150mg	90 + 6 Pills	147.18€ 140.17€	Buy
Viagra Generic	25mg	180 + 6 Pills	154.93€ 147.55€	Buy
Kamagra Oral Jelly	100mg	110 + 9 Sachets	334.87€ 318.92€	Buy

Sildenafil is only about 10-fold as potent for PDE-5 compared to PDE6, an enzyme found in the retina and involved in the phototransduction pathway of the retina.

More about sildenafil

The incidence of eye hemorrhage at both 20 mg TID and at all doses studied was 1.4% for sildenafil citrate versus 1.4% for placebo. The patients experiencing these reactions had risk factors for hemorrhage including concurrent anticoagulant therapy. In a placebo-controlled fixed dose titration study (Study 2) of sildenafil citrate (starting with recommended dose of 20 mg TID and increased to 40 mg TID and then 80 mg TID) as an adjunct to intravenous epoprostenol in patients with PAH, the adverse reactions that were more frequent in the sildenafil citrate + epoprostenol group than in the epoprostenol group (greater than 6% difference) are shown in Table 2 . The following adverse reactions have been identified during post approval use of * Sildenafil (marketed for both PAH and erectile dysfunction). Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Recreational use

In postmarketing experience with sildenafil at doses indicated for erectile dysfunction, serious cardiovascular, cerebrovascular, and vascular events, including myocardial infarction, sudden cardiac death, ventricular arrhythmia, cerebrovascular hemorrhage, transient ischemic attack, hypertension, pulmonary hemorrhage, and subarachnoid and intracerebral hemorrhages have been reported in temporal association with the use of the drug. Most, but not all, of these patients had preexisting cardiovascular risk factors. Many of these events were reported to occur during or shortly after sexual activity, and a few were reported to occur shortly after the use of sildenafil without sexual activity. Others were reported to have occurred hours to days after use concurrent with sexual activity. It is not possible to determine whether these events are related directly to sildenafil, to sexual activity, to the patient’s underlying cardiovascular disease, or to a combination of these or other factors. This lower selectivity is thought to be the basis for abnormalities related to color vision observed with higher doses or plasma levels.

Condition	Description	Recommended Dosage	Notes
Erectile Dysfunction (ED)	Difficulty achieving or maintaining an erection	50 mg before activity	Can be adjusted based on response
Pulmonary Arterial Hypertension	High blood pressure in lungs	20 mg three times daily	Prescribed under medical supervision
Off-label uses	Other potential uses	Varies	Use under healthcare provider guidance

In addition to pulmonary vascular smooth muscle and the corpus cavernosum, PDE-5 is also found in other tissues including vascular and visceral smooth muscle and in platelets.

Dosage Forms and Administration

In a rat pre- and postnatal development study, the no-observed-adverse-effect dose was 30 mg/kg/day (equivalent to 5-times the RHD on a mg/m2 basis). Pregnancy Category (AUS): There is no Australian Drug Evaluation Committee (ADEC) guidance on usage of Sildenafil in women who are pregnant. The safety and efficacy of sildenafil citrate during labor and delivery has not been studied. It is not known if sildenafil or its metabolites are excreted in human breast milk. Because many drugs are excreted in human milk, caution should be exercised when sildenafil citrate is administered to a nursing woman.

What causes an erection?

In a randomized, double-blind, multi-center, placebo-controlled, parallel-group, dose-ranging study, 234 patients with PAH, aged 1 to 17 years, body weight greater than or equal to 8 kg, were randomized, on the basis of body weight, to three dose levels of sildenafil citrate, or placebo, for 16 weeks of treatment. Most patients had mild to moderate symptoms at baseline: WHO Functional Class I (32%), II (51%), III (15%), or IV (0.4%). One-third of patients had primary PAH; two-thirds had secondary PAH (systemic-to-pulmonary shunt in 37%; surgical repair in 30%). Sixty-two percent of patients were female. The primary objective of the study was to assess the effect of sildenafil citrate on exercise capacity as measured by cardiopulmonary exercise testing in pediatric patients developmentally able to perform the test (n = 115). The inhibition of PDE-5 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.

Precautions with Alcohol

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. There is no FDA guidance on the use of Sildenafil with respect to specific gender populations. There is no FDA guidance on the use of Sildenafil with respect to specific racial populations. No dose adjustment is required (including severe impairment CLcr < 30 mL/min). No dose adjustment for mild to moderate impairment is required.

Storage Requirements

There is no FDA guidance on the use of Sildenafil in women of reproductive potentials and males. There is no FDA guidance one the use of Sildenafil in patients who are immunocompromised. FDA Package Insert for Sildenafil contains no information regarding drug monitoring. There is limited information about the IV Compatibility. In studies with healthy volunteers of single doses up to 800 mg, adverse events were similar to those sildenafil gel seen at lower doses but rates and severities were increased. Sildenafil is also marketed as Sildenafil citrate® for erectile dysfunction.

Contraindication	Explanation	Severity Level	Notes
Nitrates use	Can cause severe hypotension	Critical	Avoid concomitant use
Heart conditions	Risk of cardiovascular events	Moderate	Consult healthcare provider
Hypotension	Low blood pressure	Moderate	Use with caution
Retinal Disorders	Potential for vision impairment	Mild	Seek medical advice

Sildenafil citrate, USP 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

Country	Approval Status	Regulatory Agency	Notes
USA	Approved	FDA	For ED and pulmonary hypertension
European Union	Approved	EMA	Similar indications
India	Approved	CDSCO	Generic versions available
Australia	Approved	TGA	Prescription required

and has the following structural formula: Patients on all Sildenafil citrate doses achieved a

Chemical synthesis

Administration of sildenafil citrate did not result in a statistically significant improvement in exercise capacity in those patients. No patients died during the 16-week controlled study. After completing the 16-week controlled study, a patient originally randomized to sildenafil citrate remained on his/her dose of sildenafil citrate or, if originally randomized to placebo, was randomized to low-, medium-, or high-dose sildenafil citrate. After all patients completed 16 weeks of follow-up in the controlled study, the blind was broken and doses were adjusted as clinically indicated. Patients treated with sildenafil were followed for a median of 4.6 years (range 2 days to 8.6 years).

How should I store sildenafil?

Mortality during the long-term study, by originally assigned dose, is shown in Figure 6: During the study, there were 42 reported deaths with 37 of these deaths reported prior to a decision to titrate subjects to a lower dosage because of a finding of increased mortality with increasing sildenafil citrate doses. For the survival analysis which included 37 deaths, the hazard ratio for high dose compared to low dose was 3.9, p=0.007. Causes of death were typical of patients with PAH. Clinical studies of sildenafil citrate did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from sildenafil pink pill younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. statistically significant reduction in mean pulmonary arterial pressure (mPAP) compared to those on placebo in a study with no background vasodilators [Study 1 in Clinical Studies (14)].

Ongoing Research and Future Applications

In cases of overdose, standard supportive measures should be adopted as required. 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, 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 PDE-5. Data on other hemodynamic measures for the Sildenafil citrate 20 mg three times a day and placebo dosing regimens is displayed in Table 3.

• Sildenafil is unsuitable for individuals with severe liver disease.
• Patients should avoid alcohol consumption during treatment.
• Some side effects may resolve on their own within hours.
• Persistent side effects should prompt medical consultation.
• The drug does not cure ED but manages symptoms.
• Lifestyle changes can also improve erectile function.
• Follow your healthcare provider’s instructions precisely.

The relationship between these effects and improvements in 6minute walk distance is unknown. mPAP = mean pulmonary arterial pressure; PVR= pulmonary vascular resistance; SVR = systemic vascular resistance; RAP = right atrial pressure; CO =

• Sildenafil can enhance the effects of other blood pressure medications.
• The drug’s safety profile is well-studied with many clinical trials.
• Cardiovascular health is an important consideration when taking sildenafil.
• Long-term use requires monitoring for adverse reactions.
• Patient education helps reduce risks and optimize dosage.
• Generic sildenafil offers a cost-effective alternative to branded Viagra.
• Regular health assessments can ensure safe usage.

cardiac output; HR = heart rate *The number of patients per treatment group varied slightly for each parameter due to missing assessments.

• The medication is classified as a controlled substance in some jurisdictions.
• Over-reliance on sildenafil without addressing underlying causes is discouraged.
• Psychological counseling may benefit some patients with ED.
• Detailed medical history helps determine if sildenafil is safe.
• Education on possible side effects improves patient safety.
• The drug does not cause dependency.
• Proper use ensures maximum therapeutic benefit and safety.