Introduction Most drugs that impact the central nervous system (CNS) function by altering some aspect of the neurotransmission process. CNS drugs can act presynaptically, affecting neurotransmitter production, storage, release, or termination, or postsynaptically by activating or blocking receptors. This chapter outlines CNS neurotransmission with an emphasis on neurotransmitters involved in the action of clinically useful […]

 Overview Drugs affecting the autonomic nervous system (ANS) are categorized based on the type of neuron they target. Cholinergic drugs, discussed in this and the following chapter, act on receptors activated by acetylcholine (Ach), while adrenergic drugs act on receptors stimulated by norepinephrine or epinephrine. These drugs can either stimulate or block ANS receptors.  The […]

                 Sodium nitroprusside Sodium nitroprusside is a potent intravenous vasodilator used for managing hypertensive emergencies and severe heart failure. It dilates both arteries and veins, reducing peripheral vascular resistance and venous return. This effect is achieved by activating guanylyl cyclase, either through nitric oxide release or direct enzyme stimulation, increasing intracellular cGMP and relaxing vascular […]

Adrenoceptor antagonists, detailed in Chapter 10, encompass α- and β-adrenoceptor blockers. Among β-adrenoceptor-blocking agents, a broad array has proven effective in lowering blood pressure, each with distinct pharmacological properties that may offer therapeutic advantages in specific clinical contexts.                  Propranolol Propranolol, the initial β blocker to demonstrate efficacy against hypertension and ischemic heart disease, has […]

                              Guanethidine Guanethidine and related adrenergic neuron-blocking agents are drugs primarily used to lower blood pressure by disrupting the release of norepinephrine from postganglionic sympathetic neurons. Guanethidine, once a cornerstone in treating severe hypertension, induces profound sympathoplegia, significantly reducing sympathetic nervous system activity. However, due to its severe side effects such as marked postural hypotension, […]

Centrally acting sympatholytic drugs, once commonly used for hypertension except for clonidine, are now seldom employed. They work by decreasing sympathetic outflow from brainstem vasomotor centers while enhancing sensitivity to baroreceptor control. This approach reduces dependency on posture compared to drugs acting directly on peripheral sympathetic neurons. Methyldopa, an L-dopa analog, is metabolized to alpha-methyldopamine […]

Diuretics lower blood pressure by reducing body sodium levels. Initially, they achieve this by decreasing blood volume and cardiac output, though peripheral vascular resistance may initially rise. Over a period of 6-8 weeks, cardiac output tends to normalize while peripheral vascular resistance decreases. Sodium contributes to vascular resistance by increasing vessel stiffness and neural reactivity, […]

Antihypertensive drugs act on one or more of four anatomical control sites to interfere with the normal regulation of blood pressure . These drugs can be classified based on their primary regulatory site or mechanism . Drugs in each category typically share similar toxicities due to their common mechanisms of action. The categories are: 1. […]

Hypertension, the most prevalent cardiovascular condition, was identified in 29% of American adults in a 2007/2008 survey. Its occurrence varies by age, race, education, and other factors. Studies indicate that 60-80% of both genders will develop hypertension by age 80. Chronic high blood pressure damages blood vessels in the kidneys, heart, and brain, leading to […]

Bioavailability refers to the portion of an unaltered drug that enters the systemic circulation when administered through any route (Table 3-3). The area under the blood concentration-time curve (AUC) correlates with the extent of bioavailability if the drug’s elimination follows first-order kinetics (Figure 3-4). For intravenous drug administration, bioavailability is considered to be 100%. However, […]