Q.Which of the following is an antihistamine drug?

Chlorpheniramine maleate is an antihistamine drug; the other three options are antimicrobial/antimalarial drugs, not antihistamines.

• Ciprofloxacin - a synthetic antibacterial (fluoroquinolone antibiotic).
• Chloroquine - an antimalarial drug.
• Chloramphenicol - a broad-spectrum antibiotic. …

Analgesics are the class of chemical compounds used to relieve pain.

Drugs are classified by the biological process they affect:

• Analgesics relieve pain without causing loss of consciousness.
• Antipyretics reduce fever.
• Tranquilizers act on the central nervous system to reduce anxiety/stress.

Since the question asks specifically for the class used to relieve pain, the answer is Analgesic. (One option in the source scan was illegible/obscured and cannot be reproduced honestly.)

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Penicillin is the antibiotic among the four listed drugs.

Penicillin, obtained from the mould Penicillium notatum, kills or inhibits the growth of bacteria and is classified as an antibiotic. Codeine is a narcotic analgesic (pain-reliever) derived from opium; Equanil (meprobamate) and Valium (diazepam) are tranquiliz …

Novestrol is another name for ethinylestradiol (17α-ethynylestradiol), a synthetic steroidal estrogen, formula $C_{20}H_{24}O_2$.

In the "chemistry in everyday life" study of medicines, sex hormones and their synthetic analogues are important estrogen/progestin drugs. Novestrol is a trade/alternative name for ethinylestradiol (17α-ethynylestradiol), a semi-synthetic, orally active estrogen obtained by introducing an ethynyl (–C≡CH) group at C-17 of estradiol; this modification lets it resist first-pass metabolism, so it is used as the estrogen in most …

Among the four drugs, only Brompheniramine is an antihistamine.

Brompheniramine (a) is a classic antihistamine (H1-receptor antagonist), used to relieve allergy symptoms. Omeprazole (b) is a proton-pump inhibitor (anti-ulcer/antacid drug). Chloramphenicol (c) is a broad-spectrum antibiotic. Norethindrone/No …

Barbiturates, derivatives of barbituric acid, are used as sedative-tranquilizer drugs.

Tranquilizers are drugs used to relieve anxiety, stress and mental tension and to induce sleep. Barbituric acid and its derivatives (barbiturates, e.g. Veronal, Luminal) are a major class of such …

Phenelzine is an MAOI-class antidepressant drug.

Phenelzine is a drug belonging to the monoamine oxidase inhibitor (MAOI) class. It works by inhibiting the enzyme monoamine oxidase, which breaks down neurotransmitters such as serotonin, norepinephrine and dopamine; inhibiting this enzyme raises the levels of these neu …