Abacavir (ABC) is a nucleoside analogue reverse transcriptase inhibitor (NRTI) and is used to treat HIV and AIDS.

It is the correct answer. Valium is used as tranquilizer. Cimetidine is used as antihistamine agent. Ethinyl Estradiol and Norgestimate both have contraceptive properties and thus are used as antifertility drugs. Hence, the statements P and R are false.

Some examples of tranquilisers are included- Valium (diazepam), Librium/Novopoxide (chlordiazepoxide), Halcion (triazolam), ProSom (estazolam), Xanax, Ativan, etc. But ceftazidime is a 3^rd generation cephalosporin antibiotic.

Equanil is used as tranquiliser. Rebprazole is used as antacid. Betamethsone is used as antihistamine agent. Ofloxacin is used as broad spectrum antibiotic. Hence, the correct representation of the codes is A - 1, B - 3, C - 2, D - 4.

P. Alitame (2000 times sweeter than sucrose) is high potency sweetener and it is more stable to heating than aspartame (100 times sweeter than sucrose). Q. Ormeloxifene is one of the selective estrogen receptor, used as a contraceptive agent and as a treatment for dysfunctional uterine bleeding. R. Alka-Seltzer is the mixture of sodium bicarbonate and potassium bicarbonate used as antacid. Hence, the statement Q is only false.

In the stomach, over production of acid causes irritation, constipation 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. Novestrol (ethylnylestradiol) is used as contraceptive drug. Chlordiazepoxide is used as tranquiliser. Hence, the antacids are  - 1, 4 and 5.

Miltown is carbamate derivative, used as tranquiliser. Hence, miltown is used as tranquilizer not as antihistamine agent.

Arsphenamine, also known as Salvarsan is a drug that was introduced at the beginning of the 1910s as the first effective treatment for syphilis.

Doxorubicin is used as anticancer drug.

Tranquilisers are neurologically active drugs. These affect the message transfer mechanism from nerve to receptor. Common tranquilisers are - diazepam (Valium), chlordiazepoxide (Librium) and alprazolam (Xanax), seconal (secobarbital), etc. Emtricitabine or tenofovir is a fixed-dose combination drug for the treatment of HIV infection.
Hence, valium, equanil and seconal are used as tranquiliser drugs.

Contraceptives or antifertility drugs are birth-controlling drugs, 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. Examples are- prilosac, ranitidine, etc. Gemifloxacin is an antibiotic drug. Etomidate, marketed as Amidate, is a short acting intravenous anaesthetic agent used for the induction of general anaesthesia and for sedation.

Antihistamines reduce or block histamines, so they stop allergy symptoms. Examples are- Cetrizine, Betamethasone, dexamethasone, hydroxyzine, loratadine, clemestine, etc. Cladribine is used as chemotherapy drug.

Adefovir is a prescription medicine used to treat chronic infections with hepatitis B virus. Ceftriaxone is 3^rd generation cephalosporin used as antimicrobial agent. Zoton is used as an antacid drug. Sodium thiopental is  also known as Sodium Pentothal, thiopental, thiopentone. It is a rapid-onset short-acting barbiturate general anesthetic. Hence, the correct answer using the codes is P - 1, Q - 4, R - 2, S - 3.

P. Bithionol is an anthelmintic drug. Bithionol is also added to soaps imparting antiseptic properties. Q. Busulfan is used as anticancer agent. R. Imiquimod is a patient-applied cream used to treat certain diseases of the skin, especially, including skin cancers (basal cell carcinoma, Bowen's disease. Hence, the statement P and Q both are false.

Potassium peroxymonosulfate (PPMS) the principal ingredient in Virkon, is a wide-spectrum disinfectant used in laboratories. Virkon kills bacteria, viruses and fungi. It is used as a 1% solution in water. Arbidol or umifenovir is an antiviral drug used for influenza infections. Kava is a herbal product obtained from Piper methysticum plant and used as tranquiliser. Ifosfamide is used as anticancer drug. Hence, the correct answer using the codes is P - 3, Q - 4, R - 1, S - 2.

Buprenorphine is a semi-synthetic partial opioid agonist that is used to treat opioid addiction in higher dosages, to control moderate acute pain.

P. Gemcitabine is belonging to antimetabolite class of chemotherapy drug. Q. Dacarbazine and temozolomide both are triazine type anticancer drugs belong to the alkylating agent class.  Hence, the statement P and Q both are false.

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

Zinetac (ranitidine) is used as antacid. Erythromycin is a bacteriostatic (prevent the growth of bacterial colonies) antibacterial drug. Cefepime is a bactericidal (kill bacterial colonies) antibacterial drug. Alprazolam is used as tranquiliser. Hence, the sequence of codes A - 2, B - 1, C - 4, D - 3 is correct.

Streptozotocin or streptozocin is a naturally occurring chemical that is particularly toxic to the insulin-producing beta cells of the pancreas in mammals. It is used in medicine for treating certain cancers of the islets of Langerhans. Mefenamic acid is an analgesic drug used for inflammatory pain and heavy menstrual bleeding. Seldane (terfandine) is used as an antihistamine agent. Mafenide is Sulphonamide type antibiotic and used in the treatment of urinary tract infections. Hence, the correct sequence using the codes is A - 3, B - 1, C - 4, D - 2.