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St. John’s Wort: Side Effects, Uses, Dosage, Interaction and Precautions


FAMILY— Hypericaceae

GENUS— Hypericum

SPECIES— H. perforatum

BINOMIAL NAME— Hypericum perforatum

What Is St. John’s Wort?

St. John’s wort is a medicinal herb in the family Hypericaceae. It is also known as Amber, Chasse-diable, Fuga Daemonum, Goatweed, Hardhay, Herbe à la Brûlure, Barbe de Saint-Jean, Herbe à Mille Trous, Herbe Aux Fées, Herbe Aux Mille Vertus, Demon Chaser, Herbe Aux Piqûres, Herbe de Saint Éloi, Herbe de la Saint-Jean, Herbe du Charpentier, Herbe Percée, Hierba de San Juan, Rosin Rose, Hyperici Herba, Hypericum perforatum, Klamath Weed, Millepertuis, Millepertuis Perforé, Saynt Johannes Wort, Hypereikon, SJW or Tipton Weed.

St. John’s wort has been used in alternative medication as a likely effective aid in treating mild to moderate depression and related symptoms such as anxiety or insomnia.

St. John’s wort has been used in alternative medicine as a possibly effective aid in treating somatization disorder or hot flashes caused by menopause. Topical forms of this herb have been possibly effective in healing skin wounds, or treating skin irritation caused by psoriasis.

It is also used to treat social anxiety, hepatitis C, attention deficit hyperactivity disorder (ADHD), irritable bowel syndrome, diabetic nerve pain, or burning mouth syndrome. However, many studies have shown that St. John’s wort may not be effective in treating these conditions.


Other uses may include obsessive compulsive disorder (OCD), premenstrual syndrome (PMS), anxiety disorder, seasonal affective disorder (SAD), genital herpes or cold sores, chronic fatigue syndrome, migraine headaches, sciatic nerve pain, fibromyalgia, weight loss, or smoking cessation. However, more researches are needed to prove this.

Note— It is not clear whether this herb is effective in treating any medical condition. Medicinal use of St. John’s wort has not been approved by the FDA.


The usual dose in capsule or dry tablet form, is 300 milligrams thrice a day, with meals. It is not recommended for children. (1)


It is very important to ask your doctor before you start or stop taking any other medicine, especially (2) (3)—

  • Digoxin
  • Methadone
  • Omeprazole
  • Phenobarbital
  • Theophylline
  • Warfarin
  • Levodopa
  • HIV drugs
  • Antidepressants
  • Heart medication such as ranolazine
  • Buprenorphine
  • Irinotecan
  • Risperidone
  • Paliperidone
  • Alprazolam, midazolam
  • Combined oral contraceptives
  • Calcineurin inhibitors, cyclosporine, tacrolimus
  • Amiodarone, flecainide, mexiletine
  • Beta-blockers such as Metoprolol, carvedilol
  • Calcium channel blockers such as verapamil, diltiazem, amlodipine, pregabalin
  • Lovastatin, simvastatin, atorvastatin
  • Prescription medicines such as anti-psychotics risperidone and 9-hydroxyrisperidone (i.e. paliperidone, Xeplion or Invega)


Do not take St. John’s wort without doctor’s advice if you regularly use other medication, especially (4)

  • Antidepressants
  • Anxiety Medications
  • Cholesterol medication
  • Erectile dysfunction medications
  • Heart or blood pressure medicine
  • HIV or AIDS medications
  • Asthma or allergy medicine
  • Cough or cold medicine
  • Cancer medicine
  • An steroid
  • Medicine to treat a psychiatric disorder
  • Migraine headache medicine
  • Seizure medication
  • Stomach acid reducers to treat heartburn or gastroesophageal reflux disease (GERD)
  • Medicine to prevent organ transplant rejection
  • Medicine to treat psoriasis, rheumatoid arthritis, or other autoimmune disorders
  • Ulcer medication

Ask your doctor if it is safe for you to use this product if you have —

  • Bipolar disorder
  • Alzheimer’s dementia
  • Severe depression
  • Schizophrenia or other mental illness
  • Attention deficit hyperactivity disorder (ADHD), especially if you take methylphenidate (Ritalin)

It is advisable not to take this product if you are pregnant. It may harm an unborn baby. Ask your doctor or health care provider before using, if you are pregnant.

St. John’s wort may pass into the breast milk and may cause many side effects in an unborn baby. Ask your doctor before taking this product if you’re breast—feeding.

It is recommended not to be given to a child younger than 6 years old. St. John’s wort is thought to be possibly safe for children ages between 6 to 17 years old when taken for up to 8 weeks.

What Are The Side Effects Of St. John’s Wort?

Stop taking St. John’s wort and see your doctor if you have —

  • Skin rash or irritation
  • Severe sunburn (redness, burning, blistering) after being outdoors

If you are also taking depression medication (antidepressant) or narcotic pain medicine and have the following symptoms —

  • Nausea
  • Vomiting
  • Diarrhea
  • Agitation
  • Fever
  • Hallucinations
  • Fast heart rate
  • Fainting
  • Overactive reflexes
  • Loss of coordination

Common side effects may include —

  • Insomnia
  • Strange dreams
  • Headaches
  • Dizziness
  • Dry mouth
  • Upset stomach
  • Feeling anxious, irritable, or restless
  • Diarrhea
  • Skin rash, tingly feeling
  • Feeling tired

What Happens If I Miss A Dose?

Skip the missed dose if it is almost the time for your next scheduled dose. Do not take extra St. John’s wort to make up the missed dose.

What Happens If I Take An Overdose?

Seek emergency medical help or call the Poison Help line at 1—800—222—1222.


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