Hoodia and phentermine are dietary aids used to aid weight loss. Both substances stimulate the hypothalamus, which monitors fullness and causes appetite suppression. Individuals purchase hoodia supplements over-the-counter, but phentermine requires a physician's prescription. Hoodia and phentermine are available as capsules or tablets, but hoodia supplements are also available in chewable lozenges or herbal tea. Neither hoodia nor phentermine are without drawbacks and adverse effects.
For centuries, hunters in southern Africa consumed the cactus-like plant Hoodia gordonii for its appetite and thirst suppressant properties. The habit piqued the interest of a Dutch anthropologist in 1937, when he observed natives eating the plant after removing the thorn covered skin from the cucumber like branches. British researchers isolated a chemical they named p57, as the substance responsible for inhibiting hunger and thirst. Scientists believe the steroidal glucoside not only mimics glucose, has a potency that is 100 times stronger. Replacing glucose, the chemical supposedly tricks nerve cells of the hypothalamus into believing the body has consumed a full meal. These cells then transmit messages signaling satiety.
Phentermine belongs to the group of medications called anorectics that produce chemical reactions similar to amphetamines. Researchers suggest that the chemical compound causes the hypothalamus to trigger the production of adrenaline and the neurotransmitting chemical norephinephrine from the adrenal glands. These substances initiate a sympathetic nervous system fight or flight response, which inhibits hunger. Scientists also suggest that the combination of chemicals enhances weight loss by causing the break down of fat cells in the body.
As hoodia reportedly inhibits thirst along with hunger, persons taking the herbal supplement might be prone to dehydration. The body metabolizes hoodia through the liver, which may stress the organ when individuals combine the herb with other substances that are filtered in the same manner. Health care providers caution that as an herbal supplement, hoodia does not require federal approval and that sufficient scientific studies concerning the plant are lacking. Laboratories caution that some supplement manufacturers substitute other products for hoodia, as the number of available plants is limited.
Risks associated with phentermine include the possibility of developing primary pulmonary hypertension, or PPH. The compound may also cause vascular heart disease. Common phentermine side effects include increased heart rate and hypertension along with constipation or diarrhea. Individuals also report feeling jittery or restless. Physicians advise against taking phentermine with other stimulants or weight loss products.
Health care providers do not recommend hoodia or phentermine for patients with a history of heart disease or hypertension. Diabetics should not use hoodia, and phentermine use is ill advised for individuals with arteriosclerosis or hyperthyroidism. The recommended dose of hoodia is 1,000 milligrams one hour before meals. The phentermine dose is generally 37.5 milligrams before breakfast or 18.75 milligrams twice a day.