Travo-Z Eye Drops

Indications

• Open-angle glaucoma
• Ocular hypertension

Dosage

Children: Refer to the BNF for Children for specific dosing information.

Adults: Apply once daily, preferably in the evening.

Mechanism of action

Travoprost is a prodrug that is hydrolyzed to its active metabolite, travoprost free acid, after absorption through the cornea. This active form exhibits full agonist activity at the prostaglandin FP receptor, which increases the outflow of aqueous humour via trabecular meshwork and uveoscleral pathways, leading to reduced intraocular pressure.

Pharmacodynamics

Travoprost has a strong affinity for the prostaglandin FP receptor, showing full agonist activity within the nanomolar range. It demonstrates no significant affinity for other prostanoid or non-prostanoid receptors. The reduction in intraocular pressure begins approximately two hours post-administration, with peak effects occurring at around 12 hours, and sustained effects lasting over 24 hours from a single dose.

Pharmacokinetics

After ocular administration, travoprost is rapidly absorbed through the cornea and converted to travoprost free acid. The active metabolite's pharmacokinetic profile supports its efficacy in lowering intraocular pressure. Specific details on the distribution, metabolism, and excretion of travoprost remain limited, but its effects are largely localized to the eye.

Contra-indications

• Hypersensitivity to travoprost or any of its excipients
• Active intraocular inflammation
• Angle-closure glaucoma

Adverse effects

• Hypertrichosis
• Dry eye
• Eye discolouration
• Madarosis
• Increased pigmentation of the iris
• Eye irritation
• Asthma exacerbation
• Ocular inflammation

Interactions

• May enhance the effect of other intraocular pressure-lowering medications
• Caution with concomitant use of other prostaglandin analogues

Precautions

• Use with caution in patients with a history of asthma or respiratory disorders
• May cause changes in eye colour; particularly caution in patients with mixed coloured irides
• Patients should be advised to avoid repeated contact of the eye drop solution with skin

Pregnancy

Manufacturer advises to avoid unless potential benefit outweighs risk, as toxicity has been observed in animal studies.

Breast-feeding

Manufacturer advises to avoid, as travoprost is present in milk in animal studies.

Storage

Store at room temperature, away from light. After opening, use within 28 days.

Formulations

• {'name': 'Travoprost eye drops', 'strength': '15 micrograms/ml', 'volume': '2.5 ml'}
• {'name': 'Travoprost preservative-free eye drops', 'strength': '15 micrograms/ml', 'volume': '30 unit dose vials'}

Dosage

Children: Refer to specific drug guidelines for paediatric dosing, as this varies widely.

Adults: Refer to specific drug guidelines for adult dosing, as this varies widely.

Mechanism of action

The mechanism of action will vary depending on the specific drug referred to as 'adjust'. Generally, medications designed to 'adjust' physiological parameters may work by modulating neurotransmitter systems, altering hormonal levels, or affecting enzyme activity to achieve therapeutic effects.

Pharmacodynamics

Pharmacodynamics will depend on the specific drug, but typically involves the interaction of the drug with its receptor sites, leading to a biological response. The efficacy and potency of the drug are influenced by its affinity for the target receptors and the subsequent signaling pathways activated.

Pharmacokinetics

Pharmacokinetics, including absorption, distribution, metabolism, and excretion, will vary by drug. Common factors influencing pharmacokinetics include bioavailability, half-life, and the presence of food or other drugs that may affect the drug's metabolism and elimination from the body.

Indications

• Dose modification due to adverse drug reactions
• Therapeutic drug monitoring
• Management of drug interactions
• Adjustment for renal or hepatic impairment
• Pediatric dosing adjustments
• Geriatric dosing considerations

Dosage

Children: Refer to the BNF for Children for pediatric dosing adjustments, as they depend on various factors including age, weight, and specific clinical scenarios.

Adults: Refer to the specific drug monograph for detailed dosing information, as adjustments are highly individualized based on patient-specific factors.

Mechanism of action

The mechanism of action for adjustment is not applicable as it is not a specific drug but rather a clinical practice. However, the underlying principle involves tailoring pharmacotherapy to individual patient needs, which may include pharmacokinetic adjustments based on metabolism, clearance rates, and patient adherence.

Pharmacodynamics

Pharmacodynamics in the context of adjustment involves understanding how drugs affect the body and how different variables such as age, weight, kidney and liver function, and concomitant medications can influence the efficacy and safety of a drug regimen. Each adjustment is aimed at optimizing therapeutic outcomes while reducing toxicity.

Pharmacokinetics

Pharmacokinetics in the context of adjustment refers to the study of how the body absorbs, distributes, metabolizes, and excretes medications. Factors such as renal and hepatic function, body mass index, and age play critical roles in determining the appropriate adjustments needed in medication dosing. Understanding these parameters is essential for effective dose adjustment.

Pregnancy

Consult a healthcare professional before use, as the safety of adjustments during pregnancy may vary depending on the specific drug or treatment being adjusted.

Breast-feeding

Consult a healthcare professional before use, as the safety of adjustments during breastfeeding may depend on the specific drug or treatment being adjusted.

Storage

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

Indications

• Vulvovaginal candidiasis
• Fungal infections
• Antiseptic for minor cuts and abrasions
• Ocular antiseptic
• Insecticide in pest control

Dosage

Adults: Refer to specific guidelines for formulations. Commonly used as a 2-3% solution

Mechanism of action

Boric acid exerts its antifungal effects by disrupting the cell membrane integrity of fungi. It interferes with the synthesis of essential cellular components, leading to cell lysis and death. The acid also has mild antibacterial properties, which can help in reducing bacterial load in infected areas. The exact molecular pathways involved in these actions are not fully elucidated, but it is known to alter the pH of the environment, making it less conducive for fungal growth.

Pharmacodynamics

Boric acid demonstrates a low toxicity profile in humans when used appropriately. Its antifungal activity is primarily effective against Candida species, and it can be used as a second-line treatment for vulvovaginal candidiasis, particularly in cases of recurrent infections. The effectiveness of boric acid is also attributed to its ability to maintain an acidic environment, which is unfavorable for the growth of many pathogens. Its antiseptic properties help in reducing inflammation and promoting healing in infected tissues.

Pharmacokinetics

Boric acid is poorly absorbed through the gastrointestinal tract but can be absorbed through the skin and mucous membranes. Once absorbed, it is distributed throughout the body, with a tendency to accumulate in various tissues, including the liver and kidneys. The elimination half-life of boric acid is variable, depending on dosage and route of administration. It is primarily excreted unchanged in the urine. Due to its potential for toxicity with high systemic exposure, it is important to adhere to recommended dosages.

Contra-indications

• Hypersensitivity to boron or any component of the formulation
• Severe renal impairment

Adverse effects

• Skin irritation or rash
• Nausea
• Vomiting
• Diarrhea
• Headache
• Fatigue
• Tremors
• Confusion

Interactions

• May interact with other topical medications
• Caution with nephrotoxic agents

Precautions

• Use with caution in patients with renal insufficiency
• Careful monitoring is advised in long-term use
• Not recommended for use in large areas of broken skin

Pregnancy

Boric acid is classified as category C. Use during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

Limited data available. It is advisable to avoid use while breastfeeding.

Storage

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

Formulations

• Topical ointment
• Powder
• Solution

Indications

• Constipation
• Labor induction
• Topical treatment for skin conditions

Dosage

Children: Refer to the BNF for Children for appropriate pediatric dosing guidelines, as no specific doses are provided.

Adults: Refer to specific guidelines for adult dosing based on the formulation used and the condition being treated, as no standardized dose is provided.

Mechanism of action

Ricinoleic acid, the main active component of castor oil, acts as a stimulant laxative. It works by increasing the peristaltic movement of the intestines, which aids in the evacuation of stool. Additionally, it may inhibit the absorption of water in the intestines, resulting in softer stools. The oil is also believed to have anti-inflammatory properties, which can be beneficial in treating certain skin conditions.

Pharmacodynamics

The pharmacodynamic properties of castor oil include its ability to stimulate intestinal motility and increase the secretion of intestinal fluids. This leads to a faster transit time for stool through the bowel. In topical applications, castor oil exhibits emollient and moisturizing effects, promoting healing and soothing irritated skin. Its anti-inflammatory effects may also contribute to the reduction of swelling and pain in inflamed tissues.

Pharmacokinetics

Castor oil is absorbed in the gastrointestinal tract, where it is metabolized to ricinoleic acid. The onset of action for its laxative effect typically occurs within 2 to 6 hours after oral administration. The duration of action varies, but effects usually last for several hours. When applied topically, castor oil penetrates the skin and may provide localized effects without significant systemic absorption.

Adverse effects

• Abdominal cramps
• Diarrhea
• Nausea
• Vomiting
• Dehydration

Precautions

• Use with caution in patients with gastrointestinal disorders
• Not recommended for prolonged use
• Monitor for signs of dehydration

Pregnancy

Castor oil is generally not recommended during pregnancy due to potential uterine contractions and risk of premature labor.

Breast-feeding

Castor oil should be used with caution during breastfeeding as it may cause gastrointestinal discomfort in nursing infants.

Storage

Store in a cool, dry place, away from direct sunlight.

Formulations

• Liquid
• Capsules

Dosage

Children: Refer to the BNF for Children for appropriate dosing information in paediatric cases, especially in instances of overdose.

Adults: Refer to the BNF for specific dosing information based on clinical circumstances, particularly in cases of overdose.

Mechanism of action

Ethylene glycol is metabolized by alcohol dehydrogenase to glycoaldehyde, which is subsequently converted to glycolic, glyoxylic, and oxalic acids. These metabolites contribute to anion gap metabolic acidosis and are responsible for tissue injury through the formation of insoluble calcium oxalate crystals.

Pharmacodynamics

The toxicity of ethylene glycol arises from its metabolites, particularly glycolic and oxalic acids. These compounds induce metabolic acidosis, lead to renal failure through calcium oxalate crystal deposition in the kidneys, and can cause neurological impairment. The anion gap increases due to the accumulation of these acids, leading to complications such as cardiovascular instability and potential multi-organ failure.

Pharmacokinetics

Ethylene glycol is rapidly absorbed after oral ingestion. It undergoes first-pass metabolism primarily in the liver, where it is converted into its toxic metabolites. The elimination half-life of ethylene glycol varies but is generally prolonged in cases of renal impairment. Renal excretion of metabolites contributes to the duration of toxicity, necessitating prompt medical intervention in cases of overdose.

Adverse effects

• Metabolic acidosis
• Renal failure
• CNS depression
• Hypocalcemia
• Cardiovascular collapse
• Pulmonary edema

Precautions

• Use with caution in patients with renal impairment
• Monitor for signs of metabolic acidosis
• Evaluate electrolyte levels, particularly calcium

Pregnancy

There is limited data on the safety of ethylene glycol in pregnancy. It should only be used if clearly needed.

Breast-feeding

It is unknown if ethylene glycol is excreted in human milk. Caution is advised.

Storage

Store in a tightly closed container at room temperature, away from heat and moisture.

Formulations

• Liquid

Indications

• Adjustment of pH in pharmaceutical formulations
• Facilitation of drug absorption
• Used in sterile preparations

Dosage

Children: Refer to specific product guidelines for dosing information, as hydrochloric acid is typically used in a controlled setting based on formulation requirements.

Adults: Refer to specific product guidelines for dosing information, as hydrochloric acid is typically used in a controlled setting based on formulation requirements.

Mechanism of action

Hydrochloric acid dissociates in aqueous solution to release hydrogen ions (H+), leading to a decrease in pH. This acidic environment promotes the activation of pepsinogen to pepsin, an enzyme essential for protein digestion. Additionally, the acidity aids in the absorption of certain minerals and drugs that require an acidic environment for optimal bioavailability.

Pharmacodynamics

The primary pharmacodynamic action of hydrochloric acid is the maintenance of gastric acidity, which is essential for normal digestive processes. The acidic environment helps in denaturing proteins, activating digestive enzymes, and providing a barrier against pathogenic microorganisms. Its effects can influence the absorption and efficacy of various medications, particularly those that are pH-dependent.

Pharmacokinetics

Hydrochloric acid does not undergo significant systemic absorption when used in its normal contexts, as it acts locally within the gastrointestinal tract. The amount of hydrochloric acid produced by the stomach varies with food intake and physiological needs. It is secreted by parietal cells in the gastric mucosa, and its secretion is regulated by neural, hormonal, and local factors. The half-life of hydrochloric acid is not applicable as it is continuously produced and neutralized within the gastrointestinal tract.

Contra-indications

• Hypersensitivity to hydrochloric acid or any of its components
• Severe renal impairment
• Active gastrointestinal bleeding

Adverse effects

• Abdominal pain
• Diarrhea
• Nausea
• Vomiting
• Esophageal irritation
• Gastric mucosal irritation
• Electrolyte imbalances

Interactions

• May interact with alkaline substances, potentially neutralizing hydrochloric acid
• Caution with antacids as they may affect the efficacy of hydrochloric acid

Precautions

• Use with caution in patients with a history of gastritis or gastric ulcers
• Monitor electrolytes in prolonged use
• Use cautiously in patients with respiratory conditions due to potential aspiration risks

Pregnancy

Hydrochloric acid is classified as a category C drug. Use during pregnancy only if clearly needed and the potential benefits justify the risks to the fetus.

Breast-feeding

There is limited data on the excretion of hydrochloric acid in human milk. Use with caution during breastfeeding.

Storage

Store in a cool, dry place away from direct sunlight and heat. Ensure the container is tightly closed.

Formulations

• Oral solutions
• Injectable forms
• Tablets

Dosage

Children: Paediatric dosing information is not standardized and should be derived from specific product guidelines or expert consultation.

Adults: Dosage and usage depend on the specific hydrogenated compound and its intended therapeutic application. Refer to specific product guidelines for detailed dosing information.

Mechanism of action

Hydrogenation alters the molecular structure of fatty acids, transforming double bonds into single bonds. This process increases the saturation level of fats, which can influence their metabolic pathways and lipid profiles in the body.

Pharmacodynamics

The pharmacodynamic effects of hydrogenated compounds depend on the specific substance being hydrogenated. Generally, hydrogenated fats can affect lipid metabolism, potentially leading to increased levels of LDL cholesterol and decreased levels of HDL cholesterol when consumed in excess. The physiological effects may include changes in insulin sensitivity and inflammatory responses.

Pharmacokinetics

The pharmacokinetics of hydrogenated compounds vary widely based on the specific hydrogenated product. Generally, these compounds are absorbed in the gastrointestinal tract, where they may undergo further metabolism by enzymes. The bioavailability, distribution, metabolism, and excretion depend on the fatty acid composition and the presence of other dietary components.

Pregnancy

Hydrogenated compounds, depending on their specific type, may have varying safety profiles in pregnancy. It is essential to consult specific guidelines or studies related to the particular hydrogenated substance in question.

Breast-feeding

The safety of hydrogenated compounds during breastfeeding may vary. Consultation with healthcare professionals regarding specific substances is advisable.

Storage

Hydrogenated substances should be stored in a cool, dry place, away from direct sunlight and heat to maintain stability.

Dosage

Children: Refer to specific guidelines for pediatric dosing; consult the BNF for Children for accurate dosage information.

Adults: Refer to specific guidelines for use; dosage may vary based on the context of use.

Mechanism of action

Hydroxide ions act primarily as bases, neutralizing acids to form water and salts. They participate in various biochemical pathways, including selenium metabolism and the degradation of reactive oxygen species. Hydroxide can influence enzyme activity and stability by altering the pH of the environment, thereby affecting metabolic reactions.

Pharmacodynamics

Hydroxide ions can impact biological processes by changing the local pH, which influences enzyme activity, ion transport, and the solubility of other compounds. Their ability to neutralize acids can help regulate physiological pH, contributing to homeostasis in living organisms.

Pharmacokinetics

As an inorganic ion, hydroxide does not undergo traditional pharmacokinetic processes like absorption, distribution, metabolism, or excretion. Instead, it is rapidly equilibrated in biological fluids and participates in acid-base reactions, having immediate effects on the local environment.

Pregnancy

There is limited information regarding the use of hydroxide during pregnancy. Consult a healthcare professional for advice.

Breast-feeding

Limited data is available on the excretion of hydroxide in breast milk. Consult a healthcare professional before use.

Storage

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

Indications

• Constipation
• Bowel preparation for surgery or diagnostic procedures
• Occasional use for bowel evacuation

Dosage

Children: For children aged 1-4 years, the recommended dose is 5-10 ml of a 70% solution; for children aged 5-11 years, the dose is 10-20 ml. For children over 12 years, the adult dosing guidelines apply. Refer to the BNF for Children for specific

Adults: For adults, the typical dose is 30-150 ml of a 70% solution taken orally, depending on the severity of constipation and individual response.

Mechanism of action

Sorbitol exerts its laxative effect by drawing water into the large intestine, stimulating bowel movements. It acts as a hygroscopic agent and a local irritant, drawing water from tissues into the feces and reflexively stimulating evacuation. The biochemistry of sorbitol involves its metabolism in the polyol pathway, where it is converted from glucose by aldose reductase and further processed to fructose by sorbitol dehydrogenase, utilizing NAD(+) as a cofactor. This pathway also has implications in conditions such as diabetic retinopathy due to the activities of these enzymes.

Pharmacodynamics

Sorbitol works primarily by increasing osmotic pressure within the intestinal lumen, which results in increased water retention in the bowel. This effect softens stool and promotes peristalsis, leading to bowel evacuation. The concentration and timing of sorbitol administration can also influence its apoptotic effects in certain cancer cell lines, although this is less relevant in its primary use as a laxative.

Pharmacokinetics

Sorbitol is poorly absorbed from the gastrointestinal tract, which allows it to exert its effects primarily within the intestines. It is mainly excreted unchanged in the urine. The onset of action typically occurs within 30 minutes to 3 hours after oral administration, depending on individual factors such as gastrointestinal transit time.

Adverse effects

• Diarrhea
• Abdominal cramping
• Nausea
• Vomiting
• Electrolyte imbalance
• Dehydration

Precautions

• Use with caution in patients with renal impairment.
• Monitor electrolytes in prolonged use.
• Not recommended for patients with bowel obstruction.

Pregnancy

Sorbitol is generally considered safe for use during pregnancy when used as directed, but consult a healthcare provider.

Breast-feeding

Sorbitol is excreted in breast milk, but is typically regarded as safe during breastfeeding; consult a healthcare provider for individual cases.

Storage

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

Formulations

• Oral solution
• Powder for solution

Indications

• Constipation
• Bowel preparation before colonoscopy or surgery

Dosage

Children: Refer to specific product guidelines for dosing instructions.

Adults: Refer to specific product guidelines for dosing instructions.

Mechanism of action

Polyoxyl works by retaining water in the stool, increasing its bulk and consistency. This osmotic effect stimulates bowel movements by softening the stool and promoting peristalsis. The water-retaining properties are attributed to its high molecular weight and hydrophilicity, which allow it to attract and hold water within the gastrointestinal tract.

Pharmacodynamics

The pharmacodynamic profile of polyoxyl includes its ability to enhance stool water content, thereby improving fecal passage through the intestines. This results in increased stool frequency and decreased transit time. Polyoxyl does not significantly affect electrolyte balance, making it a safe option for chronic constipation management.

Pharmacokinetics

Polyoxyl is not absorbed systemically; it remains in the gastrointestinal tract where it exerts its effects. The onset of action can vary but typically occurs within 24 to 72 hours after administration. The elimination of polyoxyl occurs through fecal excretion, with no significant metabolism or renal clearance involved.

Adverse effects

• Nausea
• Vomiting
• Diarrhea
• Abdominal cramps
• Allergic reactions

Precautions

• Use with caution in patients with gastrointestinal disorders.
• Monitor for allergic reactions in patients with a history of hypersensitivity.

Pregnancy

Polyoxyl is generally regarded as safe for use during pregnancy, but specific clinical guidance should be consulted.

Breast-feeding

Polyoxyl is considered safe during breastfeeding, though maternal factors should be assessed.

Storage

Store at room temperature, away from moisture and heat. Keep out of reach of children.

Formulations

• Oral solution
• Tablet
• Topical cream

Indications

• Plant growth regulation
• Agricultural applications as a growth inhibitor

Dosage

Children: Not applicable.

Adults: Refer to the relevant agricultural guidelines for specific applications.

Mechanism of action

In an in vitro study, propylene acts as a plant growth inhibitor by inhibiting the oxidation of indole-3-acetic acid by peroxidase in the presence of superoxide anion radicals. This inhibition is linked to the activation of an iron complex (compound III) shuttle, which enhances the reaction rate between superoxide and peroxidase, ultimately affecting plant growth processes. Propylene is a less effective inhibitor compared to ethylene.

Pharmacodynamics

The pharmacodynamic effects of propylene are primarily observed in its role as a growth inhibitor in plants. By modulating the oxidation of phytohormones like indole-3-acetic acid, propylene can influence various growth responses in plants, potentially affecting processes such as cell elongation and division.

Pharmacokinetics

Information on the pharmacokinetics of propylene in humans is not well-documented, as its primary uses are industrial and agricultural. Its metabolism may be influenced by environmental factors, and its effects are primarily studied in the context of plant biology rather than human pharmacology.

Mechanism of action

Travoprost is a prodrug. Upon administration, travoprost is absorbed through the cornea and hydrolyzed to its active metabolite, travoprost free acid. The ester moiety of the free acid allows for enhanced penetration into the aqueous humour. While the exact mechanism of travoprost is largely unknown, it is believed to be related to its full agonist activity for the prostaglandin FP receptor. By binding to the FP receptor, travoprost free acid increases the outflow of aqueous humour via the trabecular meshwork and uveoscleral pathways, thereby reducing the intraocular pressure.

Pharmacodynamics

Travoprost demonstrates preferential affinity and full agonist activity for the prostaglandin FP receptor in the nanomolar range. Travoprost shows no significant affinity for other prostanoid or non-prostanoid receptors. Travoprost-induced reduction of intraocular pressure is observed about two hours after administration, and the maximum effect is reached after 12 hours. Significant lowering of intraocular pressure can be maintained for periods exceeding 24 hours with a single dose.

Mechanism of action

Ethylene glycol is metabolized by alcohol dehydrogenase to glycoaldehyde, which is then metabolized to glycolic, glyoxylic, and oxalic acids. These acids, along with excess lactic acid are responsible for the anion gap metabolic acidosis. Oxalic acid readily precipitates with calcium to form insoluble calcium oxalate crystals. Tissue injury is caused by widespread deposition of oxalate crystals and the toxic effects of glycolic and glyoxylic acids.

Mechanism of action

Sorbitol exerts its laxative effect by drawing water into the large intestine, thereby stimulating bowel movements. ... Sorbitol exerts hygroscopic and/or local irritant action, drawing water from tissues into feces and reflexly stimulating evacuation. The polyol pathway consists of two enzymes aldose reductase (AR) and sorbitol dehydrogenase (SDH); the former is the first enzyme in the polyol pathway, that catalyzes the reduction of glucose to sorbitol, the latter is the second one, that converts sorbitol to fructose using by NAD(+) as a cofactor. ... SDH activity, the second step in the polyol pathway, might make a greater contribution to the etiology of diabetic retinopathy than does the first step involving AR. /This paper proposes/ a novel hypothesis that polymorphisms of SDH gene may be correlated with SDH gene expression levels in diabetic retinas, thus being a valuable genetic marker for diabetic retinopathy. It has been reported that sorbitol induces apoptosis in several cancer cell lines. ... In /this/ study, the intracellular signaling pathways of sorbitol-induced apoptosis in human K562 cells were investigated using both morphological analysis and DNA fragmentation technique. In this study, we demonstrated that sorbitol-induced apoptosis in human K562 cells is a concentration- and time-dependent manner. This sorbitol-induced apoptosis in human K562 cells was also accompanied by the up-regulation of Bax, and down-regulation of p-Bcl-2, but no effect on the levels of Bcl-X(L). Moreover, the sorbitol treatment resulted in a significant reduction of mitochondria membrane potential, increase in the release of mitochondrial cytochrome c (cyt c), and activation of caspase 3. Furthermore, treatment with caspase 3 inhibitor (z-DEVD-fmk) was capable of preventing the sorbitol-induced caspase 3 activity and cell death. These results clearly demonstrate that the induction of apoptosis by sorbitol involves multiple cellular/molecular pathways and strongly suggest that pro- and anti-apoptotic Bcl-2 family proteins, mitochondrial membrane potential, mitochondrial cyt c, and caspase 3, they all participate in sorbitol-induced apoptotic process in human K562 cells. Chronic diabetic complications, in particular, nephropathy, peripheral and autonomic neuropathy, "diabetic foot," retinopathy, and cardiovascular disease, remain the major cause of morbidity and mortality in patients with diabetes mellitus. Growing evidence indicates that both increased activity of the sorbitol pathway of glucose metabolism and enhanced oxidative stress are the leading factors in the pathogenesis of diabetic complications. The relation between the two mechanisms remains the area of controversy. One group has reported that increased sorbitol pathway activity has a protective rather than detrimental role in complication-prone tissues because the pathway detoxifies toxic lipid peroxidation products. Others put forward a so-called "unifying hypothesis" suggesting that activation of several major pathways implicated in diabetic complications (eg, sorbitol pathway) occurs due to increased production of superoxide anion radicals in mitochondria and resulting poly(ADP-ribose) polymerase activation. This review (a) presents findings supporting a key role for the sorbitol pathway in oxidative stress and oxidative stress-initiated downstream mechanisms of diabetic complications, and (b) summarizes experimental evidence against a detoxifying role of the sorbitol pathway, as well as the "unifying concept."

Mechanism of action

In an in vitro study of the mechanism of action of ethylene as a plant growth inhibitor, the effects of ethylene and some of its analogs, including propylene, on the oxidation of indole-3-acetic acid were examined. Ethylene and its analogs inhibited the oxidation of indole-3-acetic acid by peroxidase under conditions where the iron complex (compound III, an oxy-ferrous complex of peroxidase) shuttle was activated. Inhibition occurred only in the presence of the superoxide anion radical 02(-). Spectral and kinetic data indicated that ethylene and its analogs enhanced the rate of reaction of 02(-) with peroxidase; ie, the iron complex (compound III) shuttle, resulting in the formation of compound III. Propylene was a less effective inhibitor than ethylene.