Patients thus taking the drug may experience colorvision abnormalities. Some complained of blurriness and loss of peripheral vision. In July 2005, the U.S. Food and Drug Administration (FDA) found that sildenafil could lead to vision impairment in rare cases, and a number of studies have linked sildenafil use with non-arteritic anterior ischemic optic neuropathy.Rare but serious adverse effects found through postmarketing surveillance include prolonged erections, severe low blood pressure, myocardial infarction (heart attack), ventricular arrhythmias, stroke, increased intraocular pressure, and sudden hearing loss. In October 2007, the FDA announced that the labeling for all PDE5 inhibitors, including sildenafil, required a more prominent warning of the potential risk of sudden hearing loss. Interactions
Care should be exercised by people who are also taking protease inhibitors for the treatment of HIV infection. Protease inhibitors inhibit the metabolism of sildenafil, effectively multiplying the plasma levels of sildenafil, increasing the incidence and severity of side effects. Those using protease inhibitors are recommended to limit their use of sildenafil to no more than one 25 mg dose every 48 hours. Other drugs that interfere with the metabolism of sildenafil include erythromycin and cimetidine, both of which can also lead to prolonged plasma half-life levels.The use of sildenafil and an α1 blocker (typically prescribed for hypertension or for urologic conditions, such as benign prostatic hypertrophy) at the same time may lead to low blood pressure, but this effect does not occur if they are taken at least 4 hours apart.
Tetanus vaccine, also known as tetanus toxoid (TT), is a toxoid vaccine used to prevent tetanus. During childhood, five doses are recommended, with a sixth given during adolescence.After three doses, almost everyone is initially immune, but additional doses every ten years are recommended to maintain immunity. A booster shot should be given within 48 hours of an injury to people whose immunization is out of date. For people with high-risk injuries who are not fully immunized, tetanus antitoxin may also be recommended.Confirming that pregnant women are up to date on tetanus immunization during each pregnancy can prevent both maternal and neonatal tetanus. The vaccine is very safe, including during pregnancy and in those with HIV/AIDS.Redness and pain at the site of injection occur in between 25% and 85% of people. Fever, feeling tired, and minor muscle pain occurs in less than 10% of people. Severe allergic reactions occur in less than one in 100,000 people.A number of vaccine combinations include the tetanus vaccine, such as DTaP and Tdap, which contain diphtheria, tetanus, and pertussis vaccines, and DT and Td, which contain diphtheria and tetanus vaccines. DTaP and DT are given to children less than seven years old, while Tdap and Td are given to those seven years old and older. The lowercase d and p denote lower strengths of diphtheria and pertussis vaccines.Tetanus antiserum was developed in 1890, with its protective effects lasting a few weeks. The tetanus toxoid vaccine was developed in 1924, and came into common use for soldiers in World War II.