Continuing Education Activity

Alpha-lipoic acid is a medication used to manage and treat chronic diseases associated with oxidative stress, such as diabetic neuropathy, and slow down the onset of metabolic syndrome by acting as an antioxidant. This activity outlines the indications, mechanism of action, contraindications, and other key elements of alpha-lipoic acid supplements in the clinical setting related to the essential points needed by members of an interprofessional team in the management treatment of oxidative stress related to chronic metabolic disorders.

Objectives:

• Identify the indications for alpha-lipoic acid supplementation.
• Describe the pathophysiology of alpha-lipoic acid toxicity.
• Explain the importance of monitoring for patients on alpha-lipoic acid supplementation.
• Summarize the risks associated with initiating alpha-lipoic acid supplementation and summarize key patient counseling points.

Indications

Alpha-Lipoic acid (ALA) is a caprylic acid-derived antioxidant. It is synthesized in the mitochondria and plays an essential role as a cofactor, assisting in the enzymatic nutrient breakdown.[1] ALA consists of a dithiol functional group that eliminates reactive oxygen species (ROS) by reducing the oxidized forms of other antioxidants.[2] The organosulfur compound was discovered in 1937 when scientists discovered a type of bacteria that uses potato juice for reproduction.[3] 

ALA has recently gained a reputation as an antioxidant. In its reduced form, dihydrolipoate reacts and neutralizes ROS, such as superoxide radicals, singlet oxygen, and hydroxyl radicals. Thus, it is extremely beneficial in several oxidative-stress-associated conditions such as ischemia-reperfusion or radiation injury.[4] 

Secondly, numerous studies have strongly supported the role of ALA in treating diabetic neuropathy. It does so by enhancing nitric oxide-mediated endothelium-dependent vasodilation, thus improving microcirculation in patients with diabetic polyneuropathy.[5] Additionally, when taken with avocado/soybean unsaponifiables, ALA is shown to significantly suppress prostaglandin E-2 production, a key cytokine in the pathogenesis of inflammation.[6]

Also, ALA possesses an excellent iron-chelation property. The thiol groups in ALA are responsible for chelating irons. By increasing the glutathione levels inside the cells, ALA and dihydrolipoate excrete various toxins, especially toxic metals, in the body. Lipoic acid preferentially binds to  Zn, Pb, and Cu. On the other hand, dihydrolipoate forms complexes with Fe, Zn, Hg, Pb, and Cu.[7]

So far, ALA has the strongest evidence of its therapeutic effect in diabetic neuropathy and oxidative stress conditions. There is still a need for more studies on its benefit in other conditions such as HIV/AIDS, liver disease, and weight loss. According to the FDA, ALA is reported to be safe and effective, and that there are promising uses that can be explored in future studies. 

Mechanism of Action

ALA's chemical reactivity is dictated by its dithiolane ring. There are two forms of ALA: oxidized lipoic acid (LA) and reduced dihydrolipoic acid (DHLA). Both are capable of scavenging a variety of ROS. DHLA is a potent antioxidant that can neutralize free radicals without becoming one in the process. Furthermore, ALA simultaneously regenerates other antioxidant factors such as vitamin C and E, subsequently increasing glutathione synthesis.[7] 

In the pathogenesis of inflammation, factor NF-kB modulates inflammatory cytokines, including interleukins (ILs) such as IL-1β and IL-6. ALA expresses its anti-inflammatory effect by inhibiting I Kappa B kinase, a converging enzyme for the activation of NF-kB, thus suppressing the activation of other inflammatory cytokines.[8]

Administration

ALA is available in the form of oral supplementation and intravenous injection. Studies postulate promising therapeutic properties in several conditions, including type 1 and 2 diabetes mellitus (DM), neuropathy, and ischemic-perfusion injury. 

Oral: Data demonstrates daily oral supplementation of 300 mg of ALA over the course of 3 months maintains and improves functional vision in type 1 and type 2 diabetes mellitus patients, respectively.[9]

Intravenous injection: The study shows evidence for IV treatment of daily 600 mg in improving positive neuropathic symptoms and neuropathic deficits.[10]

Adverse Effects

ALA is considered a safe supplementation without any side affect. One study supports the safety of the drug in which an adult can take up to 2400 mg without experiencing any harmful side effects.[11] High doses of ALA are not recommended as it doesn't provide any extra benefits. 

An ALA study in 1996 on six rhesus monkeys showed that excess lethal dose in primates would cause hepatic necrosis. Researchers noted that 3 out of 6 monkeys that received 90 mg/kg to 100 mg/kg of intravenous ALA exhibited large necrotic areas in the large muscles of their thighs, the liver, the heart, and the kidneys. This situation led the researchers to conclude that exceptionally high doses of intravenous ALA can produce the same symptoms that smaller doses prevent.[12]

Thus far, few studies have analyzed the safety of ALA supplementation in pregnant women or children. Therefore, these populations are advised to consult with their healthcare providers when considering taking ALA.

Contraindications

There were very few studies on the contraindications in using ALA. However, due to the adverse effects of ALA on animals and due to ALA's physiological effects, one should consult with a doctor before taking it if they have the following conditions:

• Liver disease
• Consumption of large amounts of alcohol
• Diabetic (ALA is known to lower blood's sugar) 
• A thyroid disorder, or
• A thiamine deficiency 

Also, one should stop using ALA immediately if an allergic reaction occurs, such as skin rash, nausea, or vomiting. There is not any established contraindication of ALA in pregnant women and infants. 

Monitoring

Even though ALA intoxication is extremely rare, close monitoring is necessary for children who are around diabetic patients, as most of the reported ALA intoxication cases belong to children ingesting ALA by accident. Also, a case of ALA intoxication was reported in which the patient attempted to commit suicide. Thus, it is worth monitoring the use of ALA in people who has suicidal thoughts or psychological issues.[13] Patients admitted to the emergency room with acute ALA poisoning usually present with tachycardia, neurologic effects, metabolic acidosis, and T wave inversion in the EKG.[14]

There is no established therapeutic index of ALA in humans. However, studies show that safety dosage has been defined in animals. The experimental values are 400 to 500 mg/kg for dogs, 30 mg/kg for cats, and 500mg/kg for mouses. In animal studies, high levels of ALA were reported to cause hepatotoxicity, apathy, confusion, and hypokinesis.[7] Therefore, it is worth monitoring when taking high doses of ALA frequently.

Toxicity

ALA is considered a safe drug generally. A daily dose of 200 to 2400 mg/day of ALA is deemed safe without side effects. However, there is no reported safety dose in children.[15]

There was a case in which a 20-month-old was admitted to the emergency room with vomiting, lethargy, involuntary movements for several hours. He was believed to have accidentally ingested four pills of 600 mg ALA, and the ingested drug amount was calculated as 226 mg/kg. He was later diagnosed with status epilepticus because of prolonged convulsions for half an hour. In the follow-up, he received treatment with midazolam infusion up to 0.8 mg/kg/h and 5 mg/kg maintenance doses of phenytoin to control seizures continuing for one hour in addition to intravenous hydration and HCO3 administration. In the following few days, he became conscious without further seizure recurrence.

In the last two decades, there have been very few reported cases of ALA toxicity in humans. Most of these cases occur in children and are treatable. Even though there is no established lethal dosage of ALA for humans, studies have shown that a high dose of 121 mg ALA/kg body weight/day was associated with alterations in liver enzymes and the function of the liver.[11] Therefore, there are potentially harmful side effects for overdosing ALA, and more studies are necessary to determine the toxicity. 

Enhancing Healthcare Team Outcomes

ALA intoxication cases are rare and happen mostly in the pediatric population. Most of the cases were accidental; therefore, better communication is needed between healthcare providers to provide the appropriate dosage and monitoring information to patients, especially to diabetic patients with children. Also, patients should always consult with their primary doctor before taking the ALA supplementation.

ALA is a generally safe supplement that can be purchased over the counter. Primary care physicians may act as frontline and provide proper dosage and safety information to the patients. Other specialists and health care professionals monitor and treat any adverse events of the supplement. Appropriate cooperation between interprofessional team members is essential to ensure the patient receives the most effective care and optimal benefits from ALA supplementation.