Calcium Channel Blocking Agents 

• Act on contractile and conductive tissues of the heart and on vascular smooth muscles 
• Prevent movement of extracellular calcium into the cell 
– Coronary and peripheral arteries dilate
– Myocardial contractility decreases 
– Depress conduction system

Therapeutic Actions
• Inhibit movement of calcium ions across the membranes of myocardial and arterial muscle cells. Altering the action potential and blocking muscle cell contraction 
• Depress myocardial contractility 
• Slow cardiac impulse formation in the conductive tissues 
• Cause a fall in BP 
 

Gastric acid neutralizers (antacids)

Antacids act primarily in the stomach and are used to prevent and treat peptic ulcer. They are also used in the treatment of Reflux esophagitis and Gastritis.

Mechanism of action: 

Antacids are alkaline substances (weak bases) that neutralize gastric acid (hydrochloric acid) they react with hydrochloric acid in the stomach to produce neutral or less acidic or poorly absorbed products and raise the pH of stomach secretion.

Antacids are divided into systemic and non-systemic.

• Systemic antacids (e.g. sodium bicarbonate) are highly absorbed into systemic circulation and enter body fluids. Therefore, they may alter acid–base balance. They can be used in the treatment of metabolic acidosis. 

Non-systemic: they do not alter acid–base balance significantly, because they are not well-absorbed into the systemic circulation. They are used as gastric antacids; and include:

• Magnesium compounds such as magnesium hydroxide and magnesium sulphate MgS2O3. They have relatively high neutralizing capacity, rapid onset of action, however, they may cause diarrhoea and hypermagnesemia.

• Aluminium compounds such as aluminium hydroxide. Generally, these have low neutralizing capacity, slow onset of action but long duration of action. They may cause constipation.

• Calcium compounds such as. These are highly effective and have a rapid onset of action but may cause hypersecretion of acid (acid - rebound) and milk-alkali syndrome (hence rarely used in peptic ulcer disease). 

Therefore, the most commonly used antacids are mixtures of aluminium hydroxide and magnesium hydroxide . 

Anticonvulsants: include carbamazepine (use when lithium not tolerated; may not be as effective) .

valproic acid (use when lithium not tolerated; rapid onset)

EPHEDRINE

It act indirectly and directly on α and β receptors. It increases blood pressure both by peripheral vasoconstriction and by increasing the cardiac output. Ephedrine also relaxes the bronchial smooth muscles.

Ephedrine stimulates CNS and produces restlessness, insomnia, anxiety and tremors.
Ephedrine produces mydriasis on local as well as systemic administration.
Ephedrine is useful for the treatment of chronic and moderate type of bronchial asthma, used as nasal decongestant and as a mydriatic without cycloplegia. It is also useful in preventing ventricular asystole in Stokes Adams syndrome.

Eicosanoid compounds

Prostaglandines, Leukotriens and Thromboxanes.

They are produced in minute amounts by all cells except RBCs and they act locally at the same site of synthesis.
These agents have many physiological processes as mediators and modulators of inflammatory reactions.

Immunosuppressive antibodies can be classified mainly into monoclonal and polyclonal antibodies, targeting specific components of the immune system.

1. Monoclonal Antibodies:

   • Basiliximab: Targets the IL-2 receptor on T cells, inhibiting T-cell activation. It is FDA approved for use in renal transplantation to prevent acute rejection.

   • Alemtuzumab: Targets CD52, a protein found on the surface of mature lymphocytes. It is used for treating chronic lymphocytic leukemia and as an induction agent in kidney transplantation.

   • Rituximab: Targets CD20 on B cells, leading to B-cell depletion. It is used in various conditions, including non-Hodgkin lymphoma and rheumatoid arthritis.

   • Daclizumab: Targets the IL-2 receptor (CD25) and is used in renal transplantation to prevent acute rejection.

   • Eculizumab: Targets complement component C5, inhibiting the complement cascade. It is used in conditions like paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome.

2. Polyclonal Antibodies:

   • Rabbit Antithymocyte Globulin (rATG): A polyclonal antibody that targets multiple T-cell surface markers, leading to T-cell depletion. It is used as an induction agent in kidney transplantation and for treating acute rejection.

   • Equine Antithymocyte Globulin (eATG): Similar to rATG, it targets T cells and is used in transplantation settings.

3. Mechanisms of Action:

   • Depletion of Immune Cells: Many antibodies work by depleting specific immune cell populations (e.g., T cells or B cells) to reduce the immune response against transplanted organs or in autoimmune diseases.

   • Blocking Activation Signals: Some antibodies block key receptors involved in T-cell activation, preventing the immune response from being initiated.

   • Inhibition of Complement Activation: Antibodies like eculizumab inhibit the complement system, which can contribute to tissue damage in antibody-mediated rejection.

4. Clinical Applications:

   • Organ Transplantation: Antibodies are commonly used to prevent rejection in kidney, liver, and heart transplants.

   • Autoimmune Diseases: They are also used in treating conditions like rheumatoid arthritis, lupus, and multiple sclerosis.

5. Potential Side Effects:

   • Infections: Due to immune suppression, patients are at increased risk of infections.
   • Allergic Reactions: Some patients may experience allergic reactions to antibody therapies.
   • Infusion Reactions: These can occur during the administration of monoclonal antibodies, leading to symptoms like fever, chills, and hypotension.