Cardiovascular system long-term effects

Long-Term Effects of ai-Receptor Deletion on the Cardiovascular System... 

The Committee found the evidence on the long-term health effects of the tested psychochemicals to be sparse. The target organs that may be involved in prolonged or delayed effects of phencyclidine are the brain and cardiovascular system. Target mental or cardiovascular effects did not take place within a week of exposure to the drug. No case reports have identified long-term effects or mental or cardiovascular effects soon after first exposure. 

The majority of toxic substances in the air are present in the gaseous state, a smaller portion being in the form of aerosols and dust. The substances from the air enter the organism via the respiratory tract (inhalation). In contrast to toxic substances occurring in water, pollutants in the atmosphere exert continuous and long-term effects. They represent a health hazard and catastrophic events can sometimes occur. They affect the cardiovascular and respiratory systems (Table 9.9). They also exert negative effects on the nervous system, increasing its instability. 

Uses Thyroid hormones (levothyroxine, T4, and liothyronine, T3) are used to treat overt hypothyroidism. In addition, supra-physiological doses of levothyroxine are widely used to reduce the risk of thyroid cancer recurrence by suppressing serum TSH concentrations. The use of levothyroxine suppressive therapy to induce shrinkage of benign thjnoid nodules remains controversial and its routine use is not recommended in view of its low efficacy and potential long-term effects on the cardiovascular system and the skeleton caused by the induction of subchnical hjrper-thyroidism [5 ]. 

There are two issues of concern which are associated with irreversible MAOIs involving the display of liver toxicity, particularly with hydrazines, and the permanent inactivation of both MAO-A and -B isoforms. The replacement of MAOs requires protein synthesis which may take up to 14 days. From the antidepressant viewpoint, only a selective blockage of serotonin metabolism may be of interest in order to increase serotonin availability. However, this long-term effect significantly reduces metabolism of a variety of other biogenic amines, which leads to their accumulation, which is not necessarily desired. This leads to an excessive availability of tyramine and others, which ultimately leads to increased release of noradrenaline that may result in the stimulation of cardiovascular sympathetic nervous system activity. As a consequence, potentially fatal hypertensive crises and cerebral haemorrhage can occur (Fig. 18.22). This phenomenon has often been termed the cheese effect, in order to reflect the fact that tyramine is present in a variety of foods such as wine, cheese and other fermented food and drink products. It would appear, however, that under carefully controlled and restricted dietary conditions such a risk can be minimised. 

Lead is toxic to the kidney, cardiovascular system, developiag red blood cells, and the nervous system. The toxicity of lead to the kidney is manifested by chronic nephropathy and appears to result from long-term, relatively high dose exposure to lead. It appears that the toxicity of lead to the kidney results from effects on the cells lining the proximal tubules. Lead inhibits the metaboHc activation of vitamin D in these cells, and induces the formation of dense lead—protein complexes, causing a progressive destmction of the proximal tubules (13). Lead has been impHcated in causing hypertension as a result of a direct action on vascular smooth muscle as well as the toxic effects on the kidneys (12,13). 

Geriatric Considerations - Summary Systemic absorption of ophthalmic drugs may occur and cause adverse effects in older adults. Since betaxolol is beta-selective, cardiovascular, respiratory and CNS adverse effects occur less frequently than with beta-nonselective topical opthalmics. These effects may still occur therefore close monitoring for systemic side effects is warranted. Betaxolol maybe less effective than the nonselective topical beta-blockers with an average lOP reduction of 18%-26%. Tachyphylaxis may occur after long-term therapy. 

---