Side effect

Frequency of side effects

• Very common, ≥ ¹⁄₁₀
• Common, ¹⁄₁₀₀ to ¹⁄₁₀
• Uncommon, ¹⁄₁₀₀₀ to ¹⁄₁₀₀
• Rare, ¹⁄₁₀₀₀₀ to ¹⁄₁₀₀₀
• Very rare, < ¹⁄₁₀₀₀₀

  Examples of therapeutic side effects

• Bevacizumab, used to slow the growth of blood vessels, has been used against dry age-related macular degeneration, as well as macular edema from diseases such as diabetic retinopathy and central retinal vein occlusion.
• Buprenorphine has been shown experimentally to be effective against severe, refractory depression.
• Bupropion, an anti-depressant, is also used as a smoking cessation aid; this indication was later approved, and the name of the smoking cessation product is Zyban. In Ontario, Canada, smoking cessation drugs are not covered by provincial drug plans; elsewhere, Zyban is priced higher than Wellbutrin, despite being the same drug. Therefore, some physicians prescribe Wellbutrin for both indications.
• Carbamazepine is an approved treatment for bipolar disorder and epileptic seizures, but it has side effects useful in treating attention-deficit hyperactivity disorder, schizophrenia, phantom limb syndrome, paroxysmal extreme pain disorder, neuromyotonia, and post-traumatic stress disorder.
• Dexamethasone and betamethasone in premature labor, to enhance pulmonary maturation of the fetus.
• Doxepin has been used to treat angiodema and severe allergic reactions due to its strong antihistamine properties.
• Gabapentin, approved for treatment of seizures and postherpetic neuralgia in adults, has side-effects which are useful in treating bipolar disorder1, essential tremor, hot flashes, migraine prophylaxis, neuropathic pain syndromes, phantom limb syndrome, and restless leg syndrome.
• Hydroxyzine, an antihistamine, is also used as an anxiolytic.
• Magnesium sulfate in obstetrics for premature labor and preeclampsia.
• Methotrexate, approved for the treatment of choriocarcinoma, is frequently used for the medical treatment of an unruptured ectopic pregnancy.
• The SSRI medication sertraline is approved as an antidepressant but delays conjugal climax in men, and thus may be supplied to those in which climax is premature.
• Sildenafil was originally intended for pulmonary hypertension; subsequently, it was discovered that it also produces erections, for which it was later marketed.
• Terazosin, an α₁-adrenergic antagonist approved to treat benign prostatic hyperplasia and hypertension, is used off-label to treat drug induced diaphoresis and hyperhidrosis.

  Examples of undesirable/unwanted side effects

• Echinacea – more than 20 different types of reactions have been reported, including asthma attacks, loss of pregnancy, hives, swelling, aching muscles and gastrointestinal upsets.
• Feverfew – pregnant women should avoid using this herb, as it can trigger uterine contractions which could lead to premature labour or miscarriage.
• Asteraceae plants – which include feverfew, echinacea, dandelion and chamomile. Side effects include allergic dermatitis and hay fever.