Clonidine Guanabenz and Guanfacine

The detailed pharmacology of the a2 adrenergic agonists clonidine (catapres), guanabenz, (wytensin), and guanfacine (tenex) is discussed in Chapter 10. These drugs stimulate the a2A subtype of a2 adrenergic receptors in the brainstem, reducing sympathetic outflow from the CNS. Patients who have had a spinal cord transection above the level of the sympathetic outflow tracts do not display a hypotensive response to clonidine. At doses higher than those required to stimulate central a2A receptors,...

Antithyroid Drugs And Other Thyroid Inhibitors

A large number of compounds interfere either directly or indirectly with the synthesis, release, or action of thyroid hormones (Table 56-2). Inhibitors are classified into four categories (1) antithyroid drugs, which interfere directly with the synthesis of thyroid hormones (2) ionic inhibitors, which block the iodide transport mechanism (3) high concentrations of iodine itself, which decrease release of thyroid hormones and may also decrease hormone synthesis and (4) radioactive iodine, which...

A1 Adrenergic Antagonists

Drugs that selectively block a1 adrenergic receptors without affecting a2 adrenergic receptors also are used in hypertension (Table 32-2). Prazosin (minipress), terazosin (Hytrin), and doxazosin (Cardura) are the agents approved in the U.S. for this indication. PHARMACOLOGICAL EFFECTS Initially, a1 adrenergic receptor antagonists reduce arteriolar resistance and increase venous capacitance this causes a sympathetically mediated reflex increase in heart rate and plasma renin activity. During...

Poorly Absorbed Sulfonamides

Sulfasalazine (azulfidine) is very poorly absorbed from the GI tract and is used in the therapy of ulcerative colitis and Crohn's disease (see Chapter 38). SULFONAMIDES FOR TOPICAL USE Sulfacetamide Sulfacetamide is the N1-acetyl-substituted derivative of sulfanilamide. Its aqueous solubility is 90 times that of sulfadiazine. This drug (isopto-cetamide, others) is employed extensively for ophthalmic infections. Very high aqueous concentrations are not irritating to the eye and are effective...

Spectrum Of Undesired Effects

In therapeutics, a drug typically produces numerous effects, but usually only one is sought as the primary goal of treatment most of the other effects are referred to as undesirable effects of that drug for that therapeutic indication. Side effects of drugs usually are nondeleterious they include effects such as dry mouth occurring with tricyclic antidepressant therapy. Some side effects may be adverse or toxic. Mechanistic categorization of toxic effects is a necessary prelude to their...

Parenteral Vasodilators

The failing left ventricle is characterized by depression of myocardial contractility and increased sensitivity to alterations of left ventricular afterload. This latter attribute of the failing ventricle is manifest by a greater proportional reduction of stroke volume as the impedance to ejection is increased. Conversely, afterload reduction in this setting can be associated with substantial increases in stroke volume. This increased afterload dependence underlies the beneficial effects of...

Selection Of Antihypertensive Drugs In Individual Patients

Choice of an antihypertensive drug should be driven by likely benefit in an individual patient, taking into account concomitant diseases such as diabetes mellitus, problematic adverse effects of specific drugs, and cost. Consensus guidelines recommend diuretics as preferred initial therapy for most patients with uncomplicated stage 1 hypertension who are unresponsive to nonpharmacological measures. Patients are also commonly treated with other drugs p receptor antagonists, ACE inhibitors A...

Pharmacotherapy Of Gout

Gout results from the precipitation of urate crystals in the tissues and the subsequent inflammatory response. Acute gout usually causes an exquisitely painful distal monoarthritis, but it also can cause joint destruction, subcutaneous deposits (tophi), and renal calculi and damage. Gout affects -0.5-1 of the population of Western countries. The pathophysiology of gout is understood poorly. While a prerequisite, hyperuricemia does not inevitably lead to gout. Uric acid, the end product of...