Avoid in individuals with a known allergy or hypersensitivity to neem (Azadirachta indica).
Side Effects and Warnings
There are few scientific reports about the safety of the above ground parts of neem. Nonetheless, several cases of death in children from neem oil poisoning have been reported. Other symptoms present in these children included vomiting, drowsiness, loose stools, metabolic acidosis, anemia, Reye-like syndrome, altered sensation and consciousness, seizures, decreased responsiveness, and liver enzyme increases with evidence of liver damage.
Taking neem bark extract by mouth for up to ten weeks appears well-tolerated in adults, as well as neem leaf extract gel for use within the mouth for up to six weeks. A 5% neem cream or 0.5-2% neem oil is also likely safe when applied on the skin as an insect repellent for up to two weeks.
Ventricular fibrillation and cardiac arrest due to neem leaf poisoning has been reported. Neem leaf extract may also cause bradycardia (slowed heart rate), heart rate abnormalities, or low blood pressure.
Although not well studied in humans, neem may cause increases in ammonia levels in the body or decreases in blood sugar. High concentrations of neem leaf extract may be inhibitory to thyroid function, particularly conversion of T3 and T4. Injections of neem oil may cause damage to the uterus and surrounding glands, mild transient eosinophilia (increased levels of white blood cells), and non-specific endometritis (inflammation of the lining of the uterus).
Margosa oil causes toxic encephalopathy (degenerative brain disease) particularly in infants and young children. Drowsiness, seizures, lethargy, and extreme exhaustion followed with coma/hyporeactivity are also possible. Use cautiously in patients with liver disease.
Pregnancy and Breastfeeding
Neem is not recommended in pregnant or breastfeeding women due to possible abortifacient (abortion inducing) and anti-implantation effects observed in animal studies. However, teratogenetic (causing malformations or defects to an embryo of foetus) effects have not been reported in animals.
Adults (18 years and older)
There is no proven safe or effective dose for neem. The bark extract in a dose of 30-60 milligrams twice daily for ten weeks by mouth has been used to treat gastroduodenal ulcers. A gel formulation containing neem extract twice a day, before bed and after breakfast, for six weeks has been used in the treatment of plaque and gingival condition. Neem cream or oil (2-5% neem oil) has shown protective effects against mosquito bites.
Children (younger than 18 years)
There is no proven safe or effective dose for neem in children, and use is not recommended.
Interactions with Drugs
Concomitant use of acetaminophen (Tylenol®) and neem leaf extract may cause liver toxicity. Caution is advised in patients taking other agents that may cause liver toxicity.
Due to possible hypotensive (blood pressure lowering) effects, neem should be used cautiously with other hypotensive agents.
Neem leaf extract may inhibit the clastogenic activity of cyclophosphamide (Cytoxan®) and mitomycin C. Patients taking chemotherapy agents should use neem with caution.
Neem may interfere with the way the body processes certain drugs using the liver's "cytochrome P450" enzyme system. Neem had synergistic activity with dillapiol, a cytochrome P450 3A4 inhibitor. Theoretically, neem may have synergistic activity with other cytochrome P450 3A4 inhibitors. Patients using any medications should check the package insert, and speak with a qualified healthcare professional, including a pharmacist, about possible interactions.
The combination of a low dose of neem leaf extract and a low dose of morphine produced an increased loss of pain sensation. Theoretically, neem and some opiate analgesics (pain relievers) may work together (synergistically) for a positive interaction, although a qualified healthcare professional, including a pharmacist should be consulted before combining therapies.
Neem may lower blood sugar levels. Caution is advised when using medications that may also lower blood sugar. Patients taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.
The use of neem extract and quinine hydrochloride has been reported to have positive (synergistic) effects in the spermicidal activity of these agents. Quinines are often used in the treatment of malaria.
Interactions with Herbs and Dietary Supplements
Neem may lower blood sugar levels. Caution is advised in patients with diabetes (high blood sugar) or hypoglycemia (low blood sugar), and in those taking herbs or supplements that may also lower blood sugar. Serum glucose levels may need to be monitored by a healthcare provider, and medication adjustments may be necessary. Blood glucose levels may require monitoring, and doses may need adjustment.
Neem may interfere with the way the body processes certain herbs or supplements using the liver's "cytochrome P450" enzyme system. Neem had synergistic activity with dillapiol, a cytochrome P450 3A4 inhibitor. Theoretically, neem may have synergistic activity with other cytochrome P450 3A4 inhibitors. Patients using any medications should check the package insert, and speak with a qualified healthcare professional, including a pharmacist, about possible interactions.
Administration of garlic and neem leaf extracts may decrease the formation of lipid peroxides and enhance the levels of antioxidants and detoxifying enzymes in stomach, as well as in the liver and circulation.
Due to possible hypotensive (blood pressure lowering) effects, neem should be used cautiously with other hypotensive herbs and supplements.