Browsing Pathways

Temocapril (trade name: Acecol) belongs to the class of drugs known as angiotensin-converting enzyme (ACE) inhibitors and is used primarily to lower high blood pressure (hypertension). This drug can also be used in the treatment of congestive heart failure and type II diabetes. Temocapril is a prodrug which, following oral administration, undergoes biotransformation in vivo into its active form temocaprilat via cleavage of its ester group by the liver. Angiotensin-converting enzyme (ACE) is a component of the body's renin–angiotensin–aldosterone system (RAAS) and cleaves inactive angiotensin I into the active vasoconstrictor angiotensin II. ACE (or kininase II) also degrades the potent vasodilator bradykinin. Consequently, ACE inhibitors decrease angiotensin II concentrations and increase bradykinin concentrations resulting in blood vessel dilation and thereby lowering blood pressure.

Temelastine is a second-generation H1-antihistamine. H1-antihistamines interfere with the agonist action of histamine at the H1 receptor and are administered to attenuate inflammatory process in order to treat conditions such as allergic rhinitis, allergic conjunctivitis, and urticaria. Reducing the activity of the NF-κB immune response transcription factor through the phospholipase C and the phosphatidylinositol (PIP2) signalling pathways also decreases antigen presentation and the expression of pro-inflammatory cytokines, cell adhesion molecules, and chemotactic factors. Furthermore, lowering calcium ion concentration leads to increased mast cell stability which reduces further histamine release. First-generation antihistamines readily cross the blood-brain barrier and cause sedation and other adverse central nervous system (CNS) effects (e.g. nervousness and insomnia). Second-generation antihistamines are more selective for H1-receptors of the peripheral nervous system (PNS) and do not cross the blood-brain barrier. Consequently, these newer drugs elicit fewer adverse drug reactions.

Temazepam is a short-acting benzodiazepine commonly used to treat panic disorders, severe anxiety, and insomnia. Temazepam allosterically binds on the benzodiazepine receptors in the post-synaptic GABA-A ligand-gated chloride channel in different sites of the central nervous system (CNS). This binding will result in an increase on the GABA inhibitory effects which is translated as an increase in the flow of chloride ions into the cell causing hyperpolarization and stabilization of the cellular plasma membrane. Benzodiazepine receptor associated GABA(a) receptors exist both peripherally and in the CNS, this activity consequently facilitates various effects like sedation, hypnosis, skeletal muscle relaxation, anticonvulsant activity, and anxiolytic action.

Telmisartan is angiotensin receptor blocker (ARB) which block the action of angiotensin II by binding to the type 1 angiotensin II receptor. Angiotensin II is a critical circulating peptide hormone that has powerful vasoconstrictive effects and increases blood pressure. Telmisartan used to treat hypertension, diabetic nephropathy, and congestive heart failure. Angiotensin has many vasoconstrictive effects by binding to angiotensin II type 1 receptors (AT1) in blood vessels, kidneys, hypothalamus, and posterior pituitary. In blood vessels AT1 receptors cause vasoconstriction in the tunica media layer of smooth muscle surrounding blood vessels increasing blood pressure. Blocking this AT1 receptor lowers the constriction of these blood vessels. AT1 receptors in the kidney are responsible for the production of aldosterone which increases salt and water retention which increases blood volume. Blocking AT1 receptors reduces aldosterone production allowing water retention to not increase. AT1 receptors in the hypothalamus are on astrocytes which inhibit the excitatory amino acid transporter 3 from up-taking glutamate back into astrocytes. Glutamate is responsible for the activation of NMDA receptors on paraventricular nucleus neurons (PVN neurons) that lead to thirst sensation. Since AT1 receptors are blocked, the inhibition of the uptake transporter is not limited decreasing the amount of glutamate activating NMDA on PVN neurons that makes the individual crave drinking less. This lowers the blood volume as well. Lastly, the AT1 receptors on posterior pituitary gland are responsible for the release of vasopressin. Vasopressin is an anti-diuretic hormone that cases water reabsorption in the kidney as well as causing smooth muscle contraction in blood vessels increasing blood pressure. Lowering angiotensin II action on activating vasopressin release inhibits blood pressure from increasing. All these effects of telmisartan contribute to an overall lowered blood pressure.

Telmisartan (also named Micardis) is an antagonist of angiotensin II receptor blockers (ARBs). Telmisartan competes with angiotensin II to bind type-1 angiotensin II receptor (AT1) in many tissues (e.g. vascular smooth muscle, the adrenal glands, etc.) to prevent increasing sodium, water reabsorption and peripheral resistance (that will lead to increasing blood pressure) via aldosterone secretion that is caused by angiotensin II. Therefore, action of telmisartan binding to AT1 will result in decreasing blood pressure. For more information on the effects of aldosterone on electrolyte and water excretion, refer to the description of the \spironolactone\:http://pathman.smpdb.ca/pathways/SMP00134/pathway or \triamterene\:http://pathman.smpdb.ca/pathways/SMP00132/pathway pathway, which describes the mechanism of direct aldosterone antagonists. Telmisartan is an effective agent for reducing blood pressure and may be used to treat essential hypertension and heart failure.