DURATEARS OINTMENT

Indications

• Dry skin
• Chapped lips
• Eczema
• Skin irritation
• Nipple soreness in breastfeeding
• Cosmetic moisturization

Dosage

Children: Apply as needed to the affected area, ensuring even coverage. Refer to specific guidelines or product information for pediatric formulations.

Adults: Apply as needed to the affected area, ensuring even coverage. Frequency of application may depend on the severity of the condition and the formulation used.

Mechanism of action

Lanolin acts as an occlusive agent that forms a barrier on the skin surface, reducing transepidermal water loss and enhancing skin hydration. Its lipid composition mimics the natural lipids found in the skin, promoting a feeling of smoothness and softness. Additionally, lanolin can aid in the delivery of other active ingredients through the skin by enhancing their absorption.

Pharmacodynamics

The emollient properties of lanolin allow it to soften and soothe the skin. Its fatty acid and alcohol content contribute to its ability to create a protective layer that prevents dehydration and irritation, particularly in conditions where the skin is compromised or dry. Lanolin's hydrating effects can lead to improved skin barrier function and overall skin appearance.

Pharmacokinetics

Lanolin is not systemically absorbed to a significant extent when applied topically, indicating a low bioavailability. Its effects are primarily local, enhancing skin hydration and protection. The duration of action can vary depending on the formulation and application frequency, but it generally provides prolonged moisturization as long as it remains on the skin.

Adverse effects

• Skin irritation
• Allergic reactions
• Rash

Precautions

• Use with caution in individuals with a known allergy to wool or lanolin
• Perform a patch test prior to widespread use

Pregnancy

Lanolin is generally considered safe for use during pregnancy, but it is advisable to consult a healthcare provider before use.

Breast-feeding

Lanolin is often used as a nipple cream for breastfeeding mothers and is considered safe when used as directed.

Storage

Store in a cool, dry place away from direct sunlight. Ensure the container is tightly closed when not in use.

Formulations

• Cream
• Ointment
• Lotion

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.