Equanil and Miltown are carbamate derivatives used as tranquilizers. Hence, Miltown is used as a tranquilizer not as an antacid.

Tranquilizers are neurologically active drugs. These affect the message transfer mechanism from nerve to receptor. Common tranquilizers are: Diazepam (Valium), Chlordiazepoxide (Librium), and Alprazolam (Xanax). An antacid is a drug/substance which neutralizes stomach acidity. Examples: Equate (mixture of CaCO₃, Al(OH)₃ and Mg(OH)₂), Omeparazole, etc. Hence, Valium, Librium and Alprazolam are used as tranquilizers.

Arsphenamine, also known as Salvarsan and compound 606, is a drug that was introduced at the beginning of the 1910s as the first effective treatment for syphilis, and was also used to treat trypanosomiasis. It is an organo-arsenic molecule, and was the first modern chemotherapeutic agent. Sahachiro Hata and Paul Ehrlich discovered the antisyphilitic activity of this compound in 1909 in Erlich's laboratory, during a survey of hundreds of newly synthesised organic arsenical compounds.

Over production of acid in the stomach causes irritation and pain. In severe cases, ulcers are developed in the stomach. Until 1970, only treatment for acidity was administration of antacids, such as sodium hydrogen carbonate (SHC) and a mixture of aluminium and magnesium hydroxide. Some common antacids are: sodium hydrogen carbonate (NaHCO₃), ranitidine, omeparazole, rebprazole, rolaid (CaCO₃ and Mg(OH)₂) etc.. Contraceptive drugs are used to control population. The estrogen derivative which is used in combination with progesterone derivative is ethynylestradiol (Novestrol). Hence, except Novestrol, all the above given drugs are antacids.

Oxytocin is a mammalian neurohypophysical hormone. It is produced by the hypothalamus and stored and secreted by the posterior pituitary gland. Oxytocin acts primarily as a neuromodulator in the brain. Oxytocin plays an important role in the neuroanatomy of intimacy, specifically in sexual reproduction, particularly during and after childbirth. It is released in large amounts after distension of the cervix and uterus during labor, facilitating birth, maternal bonding and after stimulation of the nipples, lactation. Both childbirth and milk ejection results from positive feedback mechanism.

Contraceptives are birth-control drugs and are used to prevent pregnancy. Estrogen and progestin are two female sex hormones. Combinations of estrogen and progestin work by preventing ovulation (the release of eggs from the ovaries). Examples are: Drospirenone, Ethinyl Estradiol, Desogestrel, Levonorgestrel, etc. Antacids are used to reduce the acidity in stomach. E.g- Omeparazole, Ranitidine, etc. Gemifloxacin is Quinolones or Fluoroquinolone class antibiotic.

P. Chlorine in the concentration of 0.2 to 0.4 ppm in aqueous solution and sulphur dioxide in very low concentrations, are used as disinfectants. Q. Ormeloxifene is one of the selective estrogen receptor, used as a contraceptive or as a treatment for dysfunctional uterine bleeding. R. Food preservatives prevent spoilage of food due to microbial growth. The most commonly used preservatives include table salt, sugar, vegetable oils and sodium benzoate, C₆H₅COONa. S. Alitame (2000 times sweeter than sucrose) is a high potency sweetener and it is more stable to heating than aspartame (100 times sweeter than sucrose).  Hence both P and S are incorrect. 

The agents that are used to treat the infectious cancer cells are called anticancer drugs. Examples are: Chlorambucil, Cyclophosphamide, Dacarbazine, etc. Levonorgestrel is used as an antifertility drug.

P. Busulfan is used as an anticancer agent. Q. Those effective mainly against Gram-positive or Gram-negative bacteria are narrow spectrum antibiotics. Penicillin G has a narrow spectrum and is used for streptococcal infections and Lyme disease. R. Phenothiazine and equanil both are used as tranquilizers. Hence, only the statement P is false.

Reserpine was isolated in 1952 from the dried root of Rauwolfia serpentina (Indian snakeroot), which had been known as Sarpagandha and had been used for centuries in India for the treatment of insanity, as well as fever and snakebites. Reserpine (Lannett's Serpalan) is an indole alkaloid, antipsychotic and antihypertensive drug that has been used for the control of high blood pressure and as a tranquilizer.
Some examples of tranquilizers are: Valium (diazepam), Librium/Novopoxide (chlordiazepoxide), Halcion (triazolam), ProSom (estazolam), Xanax, Ativan, etc.

Citric acid is used as an antacid to decrease acidity in stomach. Chlorpromazine is used as a tranquilizer. Commonly used antiseptic, Dettol is a mixture of chloroxylenol and terpineol. Sucrolose (600 times sweeter than sucrose) is used as an artificial sweetening agent. Hence, the correct answer using the codes is P - 3, Q - 4, R - 1, S - 2.

(P) Medroxyprogesterone is a progestin hormone, prescribed for menstrual problems, breast cancer and prevention of pregnancy. (Q) Valium and Librium are used as tranquilizers. (R) Ethinyl Estradiol and Norgestimate both have contraceptive properties and thus used as antifertility drugs. Hence, only R is false.

2-3 % alcoholic solution of iodine is called as Iodine tincture that is used as an antiseptic lotion. Chloramphenicol is bacteriostatic (prevent the growth of bacterial colonies) antibacterial agent. Ceftriaxone is bactericidal (kill bacterial colonies) antibacterial agent. Xanax or alprazolam is used as a tranquilizer. Hence, the representation of codes A - 2, B - 1, C - 4, D - 3 is correct.

Amikacin belongs to aminoglycosides. Binding to the bacterial 30S ribosomal sub-unit inhibits the translocation of the peptidyl-tRNA from the A-site to the P-site. Loracarbef is carbacephem antibiotic. It prevents bacterial cell division by inhibiting cell wall synthesis. Cephalexin is the first generation cephalosporin and it disrupts the synthesis of the peptidoglycan layer of bacterial cell walls. Linezolid belongs to oxazolidonone class and this is a protein synthesis inhibitor that prevents the initiation step. Hence, the correct answer is P - 2 - i, Q - 3 - iv, R - 4 - iii, S - 1 - ii.

Bleomycin is used as an anticancer drug (antitumor). Mafenide is Sulfonamide-type antibiotic and is used in the treatment of urinary tract infections. Betamethasone is used as an antiallergic and antihistamine agent. Triazolam is used as a tranquilizer. Hence, the correct sequence using the codes is A - 3, B - 1, C - 4, D - 2.