Any of the pairs of nucleotides connecting the complementary strands of a molecule of DNA or RNA and consisting of a purine linked to a pyrimidine by hydrogen bonds. The base pairs are adenine-thymine and guanine-cytosine in DNA, and adenine-uracil and guanine-cytosine in RNA or in hybrid DNA-RNA pairing. Base pairs may be thought of as the rungs of the DNA ladder.
Drugs used to prevent migraines include: 1  Anticonvulsants, such as topiramate. 2  AntidepressantsAntidepressants, such as amitriptyline. 3  Antihistamine , such as cyproheptadine.  Beta-blockers, such as 1  propranolol. Botulinum toxinBotulinum toxin, such as Botox.  Calcium channel blockers, such as 1  verapamil. Histamine.
BOTOXÂ® (onabotulinumtoxinA) is a prescription medicine that is injected into muscles and used to prevent headaches in adults with chronic migraine who have 15 or more days each month with headache lasting 4 or more hours each day in people 18 years or older.otox has been approved fur treating headaches that are present more than 15 days per month. It is used to prevent headaches in adults with chronic migraine who have 15 or more days each month with headache lasting 4 or more hours each day in people 18 years or older.