THYMOGAM

Indications

• Hypogammaglobulinemia
• Immunodeficiency disorders
• Autoimmune diseases (e.g., systemic lupus erythematosus)
• Certain cancers (e.g., multiple myeloma)
• Infections requiring passive immunization

Dosage

Children: Dosage varies based on the specific type and indication. Refer to established guidelines for detailed dosing information.

Adults: Dosage varies based on the specific type and indication. Refer to established guidelines for detailed dosing information.

Mechanism of action

Globulins, particularly immunoglobulins, function by binding to specific antigens (such as bacteria and viruses) and neutralizing them or marking them for destruction by other components of the immune system. They can activate the complement system, enhance phagocytosis, and facilitate the opsonization of pathogens, thus playing a vital role in the immune response.

Pharmacodynamics

The pharmacodynamics of globulins involve their ability to recognize and bind to antigens, leading to the activation of various immune pathways. This binding can trigger immune cell activation, cytokine release, and ultimately the destruction of the antigen. The efficacy of globulins in therapeutic settings is closely tied to their concentration in the plasma and their specific binding affinity to target antigens.

Pharmacokinetics

Globulins are produced primarily in the liver and lymphoid tissues. Their half-life varies significantly depending on the specific type of globulin, with immunoglobulins having half-lives ranging from days to weeks. They are transported in the bloodstream and are distributed throughout the body. The elimination of globulins occurs via proteolytic degradation and renal excretion, although certain immunoglobulins can also undergo recycling through the neonatal Fc receptor.

Adverse effects

• Allergic reactions
• Headache
• Fever
• Chills
• Nausea
• Vomiting
• Rash
• Injection site reactions

Precautions

• Use with caution in patients with a history of allergic reactions to immunoglobulins
• Monitor for signs of anaphylaxis during administration
• Consider renal function in patients receiving high doses

Pregnancy

Globulins are generally considered safe for use during pregnancy, but should be used under the guidance of a healthcare provider.

Breast-feeding

Immunoglobulins are excreted in breast milk, but are considered safe for breastfeeding mothers.

Storage

Store below 25°C. Do not freeze. Protect from light.

Formulations

• Intravenous immunoglobulin (IVIG)
• Subcutaneous immunoglobulin (SCIG)
• Intramuscular immunoglobulin (IMIG)

Indications

• Insecticide for agricultural use
• Research tool in toxicology

Dosage

Children: Refer to the BNF for Children for specific dosing and administration guidelines.

Adults: Refer to the BNF for specific dosing and administration guidelines.

Mechanism of action

Methyl parathion acts primarily by inhibiting the enzyme acetylcholinesterase, which is essential for the breakdown of the neurotransmitter acetylcholine. Its active metabolite, methyl paraoxon, is a potent inhibitor of both acetylcholinesterase and butyrylcholinesterase. The inhibition of these enzymes results in the accumulation of acetylcholine at synapses, leading to overstimulation of cholinergic receptors and resultant toxic effects.

Pharmacodynamics

The pharmacodynamics of methyl parathion involve its action as a noncompetitive inhibitor of acetylcholinesterase, causing prolonged effects of acetylcholine due to its inability to be hydrolyzed. The resultant cholinergic toxicity can lead to symptoms such as muscle twitching, respiratory distress, and potentially fatal outcomes if not treated promptly. The extent of inhibition is dose-dependent, with significant toxicity occurring after substantial enzyme inhibition.

Pharmacokinetics

Methyl parathion is absorbed through the gastrointestinal tract and can also be absorbed through the skin and respiratory tract. It is metabolized in the liver to form methyl paraoxon, which is responsible for the majority of its toxic effects. The distribution of methyl parathion in body tissues is influenced by its lipophilicity, and it is primarily excreted as metabolites in the urine. The elimination half-life and specific pharmacokinetic parameters can vary based on individual metabolism and exposure levels.

Pregnancy

There are no adequate and well-controlled studies in pregnant women. Use only if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

It is not known whether this drug is excreted in human milk. Caution is advised when administering to nursing women.

Storage

Store in a cool, dry place away from direct sunlight. Keep out of reach of children.

Formulations

• Liquid formulation

Mechanism of action

Acute poisoning ... is related to ... inhibiting action on enzyme acetylcholinesterase. Toxic manifestations generally occur only after more than 50% of plasma cholinesterase is inhibited. ... Methyl parathion ... depend on oxidative activation by replacement of thiono-sulfur with oxygen for ... toxicity. Methyl parathion has only a slight inhibitory action on acetylcholinesterase and butyrylcholinesterase, but its active metabolite, methyl paraoxon, is a potent inhibitor of both these enzymes. A study was conducted examining the inhibition of (Ca2+ and Mg2+)-ATPase by parathion (56382) and methyl parathion. Enzyme activity was assessed spectrophotometrically in pig erythrocyte membranes containing calcium2+ (Ca2+) and magnesium2+ and in solubilized membrane preparations incubated with the test agents. The enzyme response to ATP was biphasic. Equations expressing the kinetics of the substrate curves described two classes of the ATP binding active site, one with high affinity and low maximum rate and one with low affinity and high maximum rate. High affinity active sites were stimulated by low ATP concentrations (20 uM), whereas low affinity active sites were stimulated by high ATP levels (2 mM). Parathion and methylparathion dose dependently inhibited enzyme activity; parathion had a greater inhibitory effect than methylparathion. Lineweaver-Burke and Dixon plots indicated noncompetitive inhibition. Parathion and methylparathion induced enzyme inhibition occurred over a range of free calcium ion concentrations (0.5 to 5 mM); the inhibition was significantly greater at lower Ca2+ concentrations (1 to 100 uM) than at higher concentrations. The authors conclude that parathion and methylparathion inhibit ATPase activity by binding to a site on the enzyme rather than through an interaction with associated lipids. For more Mechanism of Action (Complete) data for METHYL PARATHION (6 total), please visit the HSDB record page.