Viagra ocular side effects
Viagra may cause serious vision side effects such as retinal dysfunction or complete vision loss. Other most common, but less serious ocular side effects are: blurred vision, high light sensitivity.
Viagra clinical trials demonstrated that ocular side effects happen rarely and like other side effects are dose – related. Higher doses produce more serious side effects. In clinical trials about 3 % of men taking doses of 25-50 mg of Viagra experienced blurred vision, about 11 % of men taking 100 mg doses, and about 50 % of men taking 200 mg of Viagra have vision changes. In patients using more than 600 mg vision changes were detected in practically 100% of cases. Vision changes are explained by the property of Viagra to mildly affect the enzyme PDE6. Larger doses increase the blood concentration of the medication and increase the risk of ocular side effects.
Patients with macular degeneration, diabetic retinopathy, retinitis pigmentosa or other retinal disease should consult a doctor before using Viagra. Remember that Viagra may cause complete vision loss in one or both eyes, so if you have any eye conditions, do visit a doctor.
Viagra side effects
The FDA approved Viagra use in men with erectile dysfunction only after several clinical trials. The use of Viagra was estimated in over 3,700 patients (19 to 87 years of age). In these placebo-controlled trials, only 2.5% of males from Viagra group stopped the treatment due side effects occurrence in comparison with 2.3% from placebo group. These numbers show that Viagra is well-tolerated by the majority of patients and the medication causes no or minor side effects in most men. It was detected that the incidence of side effects has been dose-dependent, so a patient should take only the dose prescribed for him and never exceed it to avoid possible side effects.
Viagra should be taken only after a doctor’s consultation. The medication will not cause serious side effects if you take it properly.
Some patients with certain conditions should be especially careful. Some health diseases may increase the possibility of Viagra side effects.
Common Viagra side effects may include:
- warmth or redness in the face, neck, or chest;
- stuffy nose;
- upset stomach;
- back pain of muscle pain.
Serious side effects happen rarely, still if they occur a patient should immediately seek medical help. These severe side effects include:
- sudden hearing loss;
- chest pain;
- irregular, fast heartbeat, tachycardia;
- shortness of breath;
- allergic reactions;
- sudden vision loss.
- painful prolonged penis erection;
Viagra administration and effect
Viagra effect depends on the physical mechanism of erection – a person should be sexual stimulated for the medication to start working. Sexual stimulation provides the release of certain chemicals in the body which are necessary for Sildenafil action.
Viagra should be used as prescribed by a doctor. Follow the doctor’s recommendations and use the dose adjusted for you. Any dose changes should be made only after the consultation with your doctor. The dose choice depends on the individual response of a patient and other unrelated conditions he may have.
Viagra is taken only when needed, 30 minutes – 1 hour before sexual activity. The medication may work within 15 minutes in some patients. A person should notice how the drug works for him individually.
The medication may be taken up to 4 hours before sex. Viagra max frequency of using is one dose per day.
Viagra effect may be impaired or delayed by food. The medication should be taken on an empty stomach.
Men taking Viagra should not give up if the medication does not work in them for the first time. They may need more attempts.
Before using Viagra (Sildenafil)
Viagra (Sildenafil) is a medication available with a doctor’s prescription. Nowadays anyone can purchase Viagra online. Whether you buy Viagra in a local pharmacy with a prescription or online without prescription it is recommended to use this medication only after a consultation with a doctor. Viagra contradict with certain medical health conditions you may have or with certain drugs you may take. So it is absolutely necessary to visit your doctor to find the right dose for you and if you have other unrelated conditions – undergo special tests.
Viagra is contraindicated with any nitrate-based medications taken for chest pain or heart disease. Viagra is not allowed to be used with other blood pressure lowering medications. Viagra in combination with any blood lowering medication may provoke a serious blood pressure reduction and lead to dangerous health state.
Other unrelated conditions that contradict with Viagra intake include:
- a recent history of a heart attack, stroke, or congestive heart failure;
- heart disease or heart rhythm problems;
- high or low blood pressure;
- coronary artery disease;
- liver or kidney impairment;
- sickle cell anemia, multiple myeloma, leukemia, hemophilia;
- a stomach ulcer;
- retinitis pigmentosa;
- a history of priapism condition (a prolonged and painful penile erection);
- Peyronie’s disease;
- traumas to the genital area.
If you have the mentioned above conditions you may need special tests before using Viagra. Your doctor will adjust you the necessary dose which you should not change without talking to your doctor first.
If your doctor recommends you to avoid sexual activity due to your serious cardiovascular status, do not take Viagra.
Viagra metabolism and elimination
Viagra (Sildenafil) is refined basically by the CYP3A4 (main way) and CYP2C9 (secondary way) hepatic microsomal isoenzymes. The basic Sildenafil metabolite is a result from N-desmethylation, and undergoes further metabolism. This main metabolite restricts selectively PDEs like Sildenafil and shows the properties for PDE5 about 50% of the parent medication. This metabolite has 40% plasma levels of those noted for Sildenafil, and thus the metabolite amounts to 20% of Viagra’s pharmacologic effects.
Sildenafil is eliminated as metabolites basically in the feces – about 80% of the received dose and in the urine – about 13% of the dose.
The half life of Sildenafil is about 4 hours, this means that during a period of 4 hours a person may get and maintain an erection. Still the response of a patient decreases after 2 hours after the oral dose. So it is recommended to take Viagra 30 minutes – 2 hours before sexual activity to receive the most pleasant results.
Viagra effect on blood pressure
Viagra effect on blood pressure was estimated during special clinical trials which revealed that the max 100 mg dose of Sildenafil given to healthy test participants decreases sitting blood pressure. The reduction in systolic/diastolic blood pressure noted in the participants was maximum 8.3/5.3 mmHg. Such blood pressure decrease was mostly observed about 1–2 hours after oral dose.
The same Viagra effect on blood pressure was observed with other doses 25 mg, 50 mg. So the effect on blood pressure is not associated to dose or plasma levels within this dosage range.
The serious Viagra effect on blood pressure was noted in patients receiving nitrate- containing medications. The concomitant use of Viagra with nitrates is contraindicated because it can produce dangerous drop in blood pressure. Men with ED and uncontrolled blood pressure or taking nitrates should consult a doctor before using Viagra.
Effects of Viagra on erectile response
Eight double-blind, placebo-controlled crossover studies were conducted to evaluate the effects of Viagra on erectile response in patients having problems with getting and keeping erections.
The patients taking part in the studies had either organic or psychogenic erectile dysfunction. The administration of Viagra to the participants (with the sexual stimulation) led to improved erections. It was estimated with the help of an objective measurement of hardness and duration of erections (RigiScan).
Most studies proved the efficacy of Viagra about an hour after the dose adjustment. The erectile response significantly increased with the dose enlargement and plasma concentration. The duration of the effect of Viagra was evaluated and stated up to 4 hours.
Viagra Mechanism of Action
The physiologically penile erection requires activation of several processes such as local release of nitric oxide (NO) in the corpus cavernosum when sexual stimulation occurs, the production of enzyme guanylate cyclase and production of cyclic guanosine monophosphate (cGMP. All these processes result in smooth muscle relaxation in the corpus cavernosum and extra inflow of blood into penile tissues.
Sildenafil enhances the effect of nitric oxide by restricting phosphodiesterase type 5 (PDE5). PDE5 is known for its effect to diminish cGMP in the corpus cavernosum. When sexual stimulation occurs nitric oxide is released, Sildenafil inhibits PDE5 and this causes enlarged levels of cGMP in the corpus cavernosum. The whole process has a smooth muscle relaxation effect. Sildenafil requires sexual stimulation to start working.
Viagra absorption and distribution
According to the results of the studies of pharmacological effects of Viagra, the medication is rapidly absorbed. It was noted that maximum plasma concentrations reached within 30 to one hour after oral administration. The reduction of absorption was monitored when Viagra was taken with a high fat meal. The delay was in Tmax of an hour and a mean reduction in Cmax of 29%. The moderate steady volume of distribution for Viagra taken orally is 105 L, indicating dissimilation into the penile tissues. The study has shown that Sildenafil and its metabolites are approximately 96% bound to plasma proteins and protein binding is not related to the complete drug concentrations.
The appearing of Sildenafil in semen of healthy volunteers was measured and presented less than 0.001% of the administered dose after 1.5 hour of oral intake.
Viagra (Sildenafil) Basics
Viagra (sildenafil) is produce in the dosage form of tablets and indicated to treat ED problems in men of different ages, still the medication is not recommended to be used in young men (younger than 18 years of old) and with caution in geriatrics. Sildenafil citrate is a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5). It loosens the muscles and improves the blood flow to the genital area.
Sildenafil citrate 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.
Viagra has a tablet formulation blue in color, rounded in shape with 25 mg, 50 mg and 100 mg of Sildenafil for oral intake. Other inactive ingredients of the tablets are: microcrystalline cellulose, anhydrous dibasic calcium phosphate, croscarmellose sodium, magnesium stearate, hypromellose, titanium dioxide, lactose, triacetin, and FD & C Blue #2 aluminum lake. If you have allergic reactions to Sildenafil citrate or to other components of Viagra, do not use the medication.
Viagra recommended dose for a healthy man is 50 mg, the dose may be changed based on the response of a patient and his tolerability to the drug. Viagra is to be taken only when necessary before sexual activity with a period or 24 hours between doses. Viagra acts after half an hour of oral administration with a max effect lasting to 4 hours. Viagra requires a person to be sexually aroused to start acting. Sildenafil has certain contraindications, most serious of which are the administration with nitrates, antihypertensive medications and other ED oral therapies.