SHANNON ARCIERO NP
Prescription History 1639623895
Nurse Practitioner - Family in North Andover, MA

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

A short-acting beta-2 adrenergic agonist that is primarily used as a bronchodilator agent to treat ASTHMA. Albuterol is prepared as a racemic mixture of R(-) and S(+) stereoisomers. The stereospecific preparation of R(-) isomer of albuterol is referred to as levalbuterol.

Albuterol (also known as salbutamol) is used to treat wheezing and shortness of breath caused by breathing problems such as asthma. It is a quick-relief medication. Albuterol belongs to a class of drugs known as bronchodilators. It works by relaxing the muscles around the airways so that they open up and you can breathe more easily. Controlling symptoms of breathing problems can decrease time lost from work or school.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

A long-acting dihydropyridine calcium channel blocker. It is effective in the treatment of ANGINA PECTORIS and HYPERTENSION.

Amlodipine is used with or without other medications to treat high blood pressure. Lowering high blood pressure helps prevent strokes, heart attacks, and kidney problems. Amlodipine belongs to a class of drugs known as calcium channel blockers. It works by relaxing blood vessels so blood can flow more easily. Amlodipine is also used to prevent certain types of chest pain (angina). It may help to increase your ability to exercise and decrease the frequency of angina attacks. It should not be used to treat attacks of chest pain when they occur. Use other medications (such as sublingual nitroglycerin) to relieve attacks of chest pain as directed by your doctor.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

A pyrrole and heptanoic acid derivative, HYDROXYMETHYLGLUTARYL-COA REDUCTASE INHIBITOR (statin), and ANTICHOLESTEREMIC AGENT that is used to reduce serum levels of LDL-CHOLESTEROL; APOLIPOPROTEIN B; and TRIGLYCERIDES. It is used to increase serum levels of HDL-CHOLESTEROL in the treatment of HYPERLIPIDEMIAS, and for the prevention of CARDIOVASCULAR DISEASES in patients with multiple risk factors.

Atorvastatin is used along with a proper diet to help lower bad cholesterol and fats (such as LDL, triglycerides) and raise good cholesterol (HDL) in the blood. It belongs to a group of drugs known as statins. It works by reducing the amount of cholesterol made by the liver. Lowering bad cholesterol and triglycerides and raising good cholesterol decreases the risk of heart disease and helps prevent strokes and heart attacks. In addition to eating a proper diet (such as a low-cholesterol/low-fat diet), other lifestyle changes that may help this medication work better include exercising, losing weight if overweight, and stopping smoking. Consult your doctor for more details.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

A semi-synthetic macrolide antibiotic structurally related to ERYTHROMYCIN. It has been used in the treatment of Mycobacterium avium intracellulare infections, toxoplasmosis, and cryptosporidiosis.

This medication is used to treat certain eye infections. It is a macrolide antibiotic that works by stopping the growth of bacteria. This medication treats only bacterial eye infections. It will not work for other types of eye infections. Unnecessary use or misuse of any antibiotic can lead to its decreased effectiveness.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

A GAMMA-AMINOBUTYRIC ACID derivative that is a specific agonist of GABA-B RECEPTORS. It is used in the treatment of MUSCLE SPASTICITY, especially that due to SPINAL CORD INJURIES. Its therapeutic effects result from actions at spinal and supraspinal sites, generally the reduction of excitatory transmission.

Baclofen is used to treat muscle spasms caused by certain conditions (such as multiple sclerosis, spinal cord injury/disease). It works by helping to relax the muscles.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

A broad-spectrum antimicrobial carboxyfluoroquinoline.

This medication is used to treat eye infections. Ciprofloxacin belongs to a class of drugs called quinolone antibiotics. It works by stopping the growth of bacteria. This medication treats only bacterial eye infections. It will not work for other types of eye infections. Unnecessary use or overuse of any antibiotic can lead to its decreased effectiveness.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

A furancarbonitrile that is one of the SELECTIVE SEROTONIN REUPTAKE INHIBITORS used as an antidepressant. The drug is also effective in reducing ethanol uptake in alcoholics and is used in depressed patients who also suffer from TARDIVE DYSKINESIA in preference to tricyclic antidepressants, which aggravate dyskinesia.

Citalopram is used to treat depression. It may improve your energy level and feelings of well-being. Citalopram is known as a selective serotonin reuptake inhibitor (SSRI). This medication works by helping to restore the balance of a certain natural substance (serotonin) in the brain.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

An anticonvulsant used for several types of seizures, including myotonic or atonic seizures, photosensitive epilepsy, and absence seizures, although tolerance may develop. It is seldom effective in generalized tonic-clonic or partial seizures. The mechanism of action appears to involve the enhancement of GAMMA-AMINOBUTYRIC ACID receptor responses.

Clonazepam is used to prevent and control seizures. This medication is known as an anticonvulsant or antiepileptic drug. It is also used to treat panic attacks. Clonazepam works by calming your brain and nerves. It belongs to a class of drugs called benzodiazepines.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

A non-steroidal anti-inflammatory agent (NSAID) with antipyretic and analgesic actions. It is primarily available as the sodium salt.

See also Warning section. This medication is used to relieve joint pain from arthritis. Diclofenac belongs to a class of drugs known as nonsteroidal anti-inflammatory drugs (NSAIDs). If you are treating a chronic condition such as arthritis, ask your doctor about non-drug treatments and/or using other medications to treat your pain.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

A synthetic tetracycline derivative with similar antimicrobial activity.

This medication is used to treat a wide variety of bacterial infections, including those that cause acne. This medication is also used to prevent malaria. This medication is known as a tetracycline antibiotic. It works by stopping the growth of bacteria. This antibiotic treats only bacterial infections. It will not work for viral infections (such as common cold, flu). Using any antibiotic when it is not needed can cause it to not work for future infections.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

An azetidine derivative and ANTICHOLESTEREMIC AGENT that inhibits intestinal STEROL absorption. It is used to reduce total CHOLESTEROL; LDL CHOLESTEROL, and APOLIPOPROTEINS B in the treatment of HYPERLIPIDEMIAS.

Ezetimibe is used along with a low cholesterol/low fat diet and exercise to help lower cholesterol in the blood. Ezetimibe may be used alone or with other drugs (such as statins or fibrates). Ezetimibe works by reducing the amount of cholesterol your body absorbs from your diet. Reducing cholesterol may help prevent strokes and heart attacks.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

A competitive histamine H2-receptor antagonist. Its main pharmacodynamic effect is the inhibition of gastric secretion.

Famotidine is used to treat ulcers of the stomach and intestines and to prevent intestinal ulcers from coming back after they have healed. This medication is also used to treat certain stomach and throat (esophagus) problems (such as erosive esophagitis, gastroesophageal reflux disease-GERD, Zollinger-Ellison syndrome). It works by decreasing the amount of acid your stomach makes. It relieves symptoms such as cough that doesn't go away, stomach pain, heartburn, and difficulty swallowing. Famotidine belongs to a class of drugs known as H2 blockers. This medication is also available without a prescription. It is used to prevent and treat heartburn and other symptoms caused by too much acid in the stomach (acid indigestion). If you are taking this medication for self-treatment, it is important to read the manufacturer's package instructions carefully so you know when to consult your doctor or pharmacist.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

A benzoic-sulfonamide-furan. It is a diuretic with fast onset and short duration that is used for EDEMA and chronic RENAL INSUFFICIENCY.

Furosemide is used to reduce extra fluid in the body (edema) caused by conditions such as heart failure, liver disease, and kidney disease. This can lessen symptoms such as shortness of breath and swelling in your arms, legs, and abdomen. This drug is also used to treat high blood pressure. Lowering high blood pressure helps prevent strokes, heart attacks, and kidney problems. Furosemide is a water pill (diuretic) that causes you to make more urine. This helps your body get rid of extra water and salt.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

A cyclohexane-gamma-aminobutyric acid derivative that is used for the treatment of PARTIAL SEIZURES; NEURALGIA; and RESTLESS LEGS SYNDROME.

Gabapentin is used with other medications to prevent and control seizures. It is also used to relieve nerve pain following shingles (a painful rash due to herpes zoster infection) in adults. Gabapentin is known as an anticonvulsant or antiepileptic drug.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

A thiazide diuretic often considered the prototypical member of this class. It reduces the reabsorption of electrolytes from the renal tubules. This results in increased excretion of water and electrolytes, including sodium, potassium, chloride, and magnesium. It is used in the treatment of several disorders including edema, hypertension, diabetes insipidus, and hypoparathyroidism.

This medication is used to treat high blood pressure. Lowering high blood pressure helps prevent strokes, heart attacks, and kidney problems. Hydrochlorothiazide belongs to a class of drugs known as diuretics/water pills. It works by causing you to make more urine. This helps your body get rid of extra salt and water. This medication also reduces extra fluid in the body (edema) caused by conditions such as heart failure, liver disease, or kidney disease. This can lessen symptoms such as shortness of breath or swelling in your ankles or feet.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

A non-steroidal anti-inflammatory agent with analgesic, antipyretic, and anti-inflammatory properties

Ibuprofen is used to help relieve mild to moderate pain. When used with an opioid (such as morphine), it may be used to relieve moderate to severe pain. It is also used to reduce fever. Ibuprofen is known as a nonsteroidal anti-inflammatory drug (NSAID). It works by blocking your body's production of certain natural substances that cause inflammation. This effect helps to decrease swelling, pain, or fever.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

The major hormone derived from the thyroid gland. Thyroxine is synthesized via the iodination of tyrosines (MONOIODOTYROSINE) and the coupling of iodotyrosines (DIIODOTYROSINE) in the THYROGLOBULIN. Thyroxine is released from thyroglobulin by proteolysis and secreted into the blood. Thyroxine is peripherally deiodinated to form TRIIODOTHYRONINE which exerts a broad spectrum of stimulatory effects on cell metabolism.

Levothyroxine is used to treat an underactive thyroid (hypothyroidism). It replaces or provides more thyroid hormone, which is normally produced by the thyroid gland. Low thyroid hormone levels can occur naturally or when the thyroid gland is injured by radiation/medications or removed by surgery. Having enough thyroid hormone is important for maintaining normal mental and physical activity. In children, having enough thyroid hormone is important for normal mental and physical development. This medication is also used to treat other types of thyroid disorders (such as thyroid cancer). This medication should not be used to treat infertility unless it is caused by low thyroid hormone levels.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

One of the ANGIOTENSIN-CONVERTING ENZYME INHIBITORS (ACE inhibitors), orally active, that has been used in the treatment of hypertension and congestive heart failure.

Lisinopril is used to treat high blood pressure. Lowering high blood pressure helps prevent strokes, heart attacks, and kidney problems. It is also used to treat heart failure and to improve survival after a heart attack. Lisinopril belongs to a class of drugs known as ACE inhibitors. It works by relaxing blood vessels so blood can flow more easily.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

A benzodiazepine used as an anti-anxiety agent with few side effects. It also has hypnotic, anticonvulsant, and considerable sedative properties and has been proposed as a preanesthetic agent.

This medication is used to treat serious seizures that do not stop (status epilepticus). It is also used before surgeries or procedures to cause drowsiness, decrease anxiety, and cause forgetfulness about the procedure or surgery. Lorazepam belongs to a class of medications called benzodiazepines, which produce a calming effect on the brain and nerves (central nervous system). It is thought to work by increasing the effect of a certain natural chemical (GABA) in the brain.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

An antagonist of ANGIOTENSIN TYPE 1 RECEPTOR with antihypertensive activity due to the reduced pressor effect of ANGIOTENSIN II.

Losartan is used to treat high blood pressure (hypertension) and to help protect the kidneys from damage due to diabetes. It is also used to lower the risk of strokes in patients with high blood pressure and an enlarged heart. Lowering high blood pressure helps prevent strokes, heart attacks, and kidney problems. Losartan belongs to a class of drugs called angiotensin receptor blockers (ARBs). It works by relaxing blood vessels so that blood can flow more easily.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

This drug is used to treat high blood pressure. It is also used to lower the risk of strokes in patients with high blood pressure and an enlarged heart. Lowering high blood pressure helps prevent strokes, heart attacks, and kidney problems. This product contains two medications: losartan and hydrochlorothiazide. Losartan is an angiotensin receptor blocker (ARB) and works by relaxing blood vessels so that blood can flow more easily. Hydrochlorothiazide is a water pill (diuretic) that causes you to make more urine, which helps your body get rid of extra salt and water.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

A biguanide hypoglycemic agent used in the treatment of non-insulin-dependent diabetes mellitus not responding to dietary modification. Metformin improves glycemic control by improving insulin sensitivity and decreasing intestinal absorption of glucose. (From Martindale, The Extra Pharmacopoeia, 30th ed, p289)

Metformin is used with a proper diet and exercise program and possibly with other medications to control high blood sugar. It is used in patients with type 2 diabetes. Controlling high blood sugar helps prevent kidney damage, blindness, nerve problems, loss of limbs, and sexual function problems. Proper control of diabetes may also lessen your risk of a heart attack or stroke. Metformin works by helping to restore your body's proper response to the insulin you naturally produce. It also decreases the amount of sugar that your liver makes and that your stomach/intestines absorb.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

A selective adrenergic beta-1 blocking agent that is commonly used to treat ANGINA PECTORIS; HYPERTENSION; and CARDIAC ARRHYTHMIAS.

This medication is a beta-blocker used to treat chest pain (angina), heart failure, and high blood pressure. Lowering high blood pressure helps prevent strokes, heart attacks, and kidney problems. This drug works by blocking the action of certain natural chemicals in your body (such as epinephrine) that affect the heart and blood vessels. This lowers heart rate, blood pressure, and strain on the heart.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

Macrolide antifungal antibiotic complex produced by Streptomyces noursei, S. aureus, and other Streptomyces species. The biologically active components of the complex are nystatin A1, A2, and A3.

Nystatin is used to treat fungal skin infections. Nystatin is an antifungal that works by stopping the growth of fungus.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

A 4-methoxy-3,5-dimethylpyridyl, 5-methoxybenzimidazole derivative of timoprazole that is used in the therapy of STOMACH ULCERS and ZOLLINGER-ELLISON SYNDROME. The drug inhibits an H(+)-K(+)-EXCHANGING ATPASE which is found in GASTRIC PARIETAL CELLS.

Omeprazole is used to treat certain stomach and esophagus problems (such as acid reflux, ulcers). It works by decreasing the amount of acid your stomach makes. It relieves symptoms such as heartburn, difficulty swallowing, and cough. This medication helps heal acid damage to the stomach and esophagus, helps prevent ulcers, and may help prevent cancer of the esophagus. Omeprazole belongs to a class of drugs known as proton pump inhibitors (PPIs). If you are self-treating with this medication, over-the-counter omeprazole products are used to treat frequent heartburn (occurring 2 or more days a week). Since it may take 1 to 4 days to have full effect, these products do not relieve heartburn right away. For over-the-counter products, carefully read the package instructions to make sure the product is right for you. Check the ingredients on the label even if you have used the product before. The manufacturer may have changed the ingredients. Also, products with similar brand names may contain different ingredients meant for different purposes. Taking the wrong product could harm you.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

Semaglutide is used with a proper diet and exercise program to control high blood sugar in people with type 2 diabetes. Controlling high blood sugar helps prevent kidney damage, blindness, nerve problems, loss of limbs, and sexual function problems. Semaglutide is also used in people with type 2 diabetes and heart disease to lower the risk of death from heart attack or stroke. Semaglutide is similar to a natural hormone in your body (incretin). It works by causing insulin release in response to high blood sugar (such as after a meal) and decreasing the amount of sugar your liver makes. If you use insulin, semaglutide is not a substitute for insulin treatment.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

2-pyridinylmethylsulfinylbenzimidazole proton pump inhibitor that is used in the treatment of GASTROESOPHAGEAL REFLUX and PEPTIC ULCER.

Pantoprazole is used to treat certain stomach and esophagus problems (such as acid reflux). It works by decreasing the amount of acid your stomach makes. This medication relieves symptoms such as heartburn, difficulty swallowing, and cough. It helps heal acid damage to the stomach and esophagus, helps prevent ulcers, and may help prevent cancer of the esophagus. Pantoprazole belongs to a class of drugs known as proton pump inhibitors (PPIs).

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

A synthetic anti-inflammatory glucocorticoid derived from CORTISONE. It is biologically inert and converted to PREDNISOLONE in the liver.

Prednisone is used to treat conditions such as arthritis, blood disorders, breathing problems, severe allergies, skin diseases, cancer, eye problems, and immune system disorders. Prednisone belongs to a class of drugs known as corticosteroids. It decreases your immune system's response to various diseases to reduce symptoms such as swelling and allergic-type reactions.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

A HYDROXYMETHYLGLUTARYL-COA-REDUCTASE INHIBITOR, or statin, that reduces the plasma concentrations of LDL-CHOLESTEROL; APOLIPOPROTEIN B, and TRIGLYCERIDES while increasing HDL-CHOLESTEROL levels in patients with HYPERCHOLESTEROLEMIA and those at risk for CARDIOVASCULAR DISEASES.

Rosuvastatin is used along with a proper diet to help lower bad cholesterol and fats (such as LDL, triglycerides) and raise good cholesterol (HDL) in the blood. It belongs to a group of drugs known as statins. It works by reducing the amount of cholesterol made by the liver. Lowering bad cholesterol and triglycerides and raising good cholesterol decreases the risk of heart disease and helps to prevent strokes and heart attacks. In addition to eating a proper diet (such as a low cholesterol/low-fat diet), other lifestyle changes that may help this medication work better include exercising, losing weight if overweight, and stopping smoking. Talk with your doctor for more details.

Note on Expenses: These indicators represent gross infrastructure resource tracking paid directly to supply pharmacy networks by Medicare Part D configurations. These calculations do not track individual patient insurance tier copays or out-of-pocket shelf prices at retail checkout lanes.

Sertraline is used to treat depression, panic attacks, obsessive compulsive disorder, post-traumatic stress disorder, social anxiety disorder (social phobia), and a severe form of premenstrual syndrome (premenstrual dysphoric disorder). This medication may improve your mood, sleep, appetite, and energy level and may help restore your interest in daily living. It may decrease fear, anxiety, unwanted thoughts, and the number of panic attacks. It may also reduce the urge to perform repeated tasks (compulsions such as hand-washing, counting, and checking) that interfere with daily living. Sertraline is known as a selective serotonin reuptake inhibitor (SSRI). It works by helping to restore the balance of a certain natural substance (serotonin) in the brain.