Hypotension inhibitors

Normally, dietary tyramine is broken down in the gastrointestinal tract by MAO and is not absorbed. In the presence of MAOI, however, all of its potent sympathomimetic actions are seen. Other side effects of MAOI include excessive CNS stimulation, orthostatic hypotension, weight gain, and in rare cases hepatotoxicity. Because the monoamine oxidase inhibitors exhibit greater toxicity, yet no greater therapeutic response than other, newer agents, clinical use has been markedly curtailed. The primary use for MAOIs is in the treatment of atypical depressions, eg, those associated with increased appetite, phobic anxiety, hypersomnolence, and fatigues, but not melancholia (2). 

However, it is also the major reason for the adverse side effects of ACE inhibitors, namely cough and angio-oedema. Another observed side effect, first-dose orthostatic hypotension, is probably due to both angiotensin inhibition and kinin potentiation. 

The adverse reactions most often associated with the administration of the COMT inhibitors include disorientation, confusion, light-headedness, dizziness, dyskinesias, hyperkinesias, nausea, vomiting, hallucinations, and fever. Other adverse reactions are orthostatic hypotension, sleep disorders, excessive dreaming, somnolence, and muscle cramps. A serious and possibly fatal adverse reaction that can occur with the administration of tolcapone is liver failure... 

These dm are contraindicated in patients with a hypersensitivity to the dragp and during pregnancy (Category C) and lactation. Tolcapone is contraindicated in patients with liver dysfunction. The COMT inhibitors are used with caution in patients with hypertension, hypotension, and decreased hepatic or renal function. 

When dextromethorphan is administered with the monoamine oxidase inhibitors (see Chap. 31), patients may experience hypotension, fever, nausea, jerking motions to the leg, and coma... 

The hypotensive effects of most antihypertensive dru are increased when administered with diuretics and other antihypertensives. Many dnigp can interact with the antihypertensive drugs and decrease their effectiveness (eg, antidepressants, monoamine oxidase inhibitors, antihistamines, and sympathomimetic bronchodilators). When the ACE inhibitors are administered with the NSAIDs, their antihypertensive effect may be decreased. Absorption of the ACE inhibitors may be decreased when administered with the antacids. Administration of potassium-sparing diuretics or potassium supplements concurrently with the ACE inhibitors may cause hyperkalemia. When the angiotensin II receptor agonists are administered with... 

Category X) and lactation. The HMG-CoA reductase inhibitors are used cautiously in patients with a history of alcoholism, acute infection, hypotension, trauma, endocrine disorders, visual disturbances, and myopathy. 

Despite their clear benefits, ACE inhibitors are still underutilized in HF. One reason is undue concern or confusion regarding absolute versus relative contraindications for their use. Absolute contraindications include a history of angioedema, bilateral renal artery stenosis, and pregnancy. Relative contraindications include unilateral renal artery stenosis, renal insufficiency, hypotension, hyperkalemia, and cough. Relative contraindications provide a warning that close monitoring is required, but they do not necessarily preclude their use. 

Angiotensin receptor blockers show similar tolerability to ACE inhibitors with regard to hypotension and hyperkalemia, but they do not induce cough since ARBs do not cause an accumulation of bradykinin. Angiotensin receptor blockers can be considered in patients with ACE inhibitor-induced angioedema, but they should be initiated cautiously, as crossreactivity has been reported. Many of the other considerations for the use of ARBs are similar to those of ACE inhibitors,... 

Besides hypotension, the most frequent adverse reaction to an ACE inhibitor is cough, which may occur in up to 30% of patients. Patients with an ACE inhibitor cough and either clinical signs of heart failure or LVEF less than 40% may be prescribed an ARB.3 Other, less common but more serious adverse effects to ACE inhibitors and ARBs include acute renal failure, hyperkalemia, and angioedema. 

Angiotensi n-converti ng Hypotension, cough (with ACE inhibitors), BP every 2 hours x 3 for first dose, then every shift during oral... 

Carbidopa, a dopa-decarboxylase inhibitor, is added to the levodopa in order to decrease the peripheral conversion of levodopa to dopamine. It does not cross the blood-brain barrier and does not interfere with levodopa conversion in the brain. Concomitant administration of carbidopa and levodopa allows for lower levodopa doses and minimizes levodopa peripheral side effects such as nausea, vomiting, anorexia, and hypotension. For most patients, at least 75 to 100 mg daily of carbidopa is required to adequately block dopamine decarboxylase in the peripheral metabolism of levodopa in most patients. Taking extra carbidopa may reduce nausea related to initiating levodopa.8,16... 

Stress ulcer prophylaxis is recommended in septic patients. Patients at greatest risk for stress ulcers are coagulopathic, mechanically ventilated, and hypotensive. Histamine-receptor antagonists are more efficacious than sucralfate, and proton pump inhibitors have not been compared to histamine-receptor antagonists. However, they do demonstrate equivalence in the ability to increase gastric pH.24... 

Teniposide, a topoisomerase II inhibitor, is administered as an infusion over 30 to 60 minutes to prevent hypotension. The pharmacokinetics are described by a three-compartment model, with an a half-life of 0.75 hours, a (5 half-life of 4 hours, and a terminal half-life of 20 hours. Considerable variability in clearance of teniposide in children has been reported.17 Teniposide has shown activity in the treatment of acute lymphocytic leukemia, neuroblastoma, and non-Hodgkin s lymphoma. Side effects include myelosuppression, nausea, vomiting, mucositis, and venous irritation. Hypersensitivity reactions may be life-threatening. 

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