Dapsone has been the world wide standard for treatment of leprosy. The other agents listed are used in treatment of tuberculosis.

Zidovudine (ZDV,) formerly called azidothymidine, is active orally and is distributed to most tissues. The primary toxic side effect of ZDV is bone marrow suppression leading to anemia and neutropenia, which may require transfusions. Additional side effects include thrombocytopenia, gastrointestinal distress, headache, myalgia, acute cholestatic hepatitis, agitation, and insomnia. 

The other choices are incorrect. Acyclovir is commonly used for the treatment of mucocutaneous and genital herpes lesions and for prophylaxis in AIDS. Acyclovir has no significant toxicity on the bone marrow. Nelfinavir is a protease inhibitor that is characterized by a short half-life and has a number of drug interactions but its primary adverse effect is diarrhea and it has the most favorable safety profile in pregnancy. It is not associated with bone marrow suppression. Lamivudine is a nucleoside inhibitor and is an active inhibitor of HIV reverse transcriptase. It is used in the treatment of hepatitis B virus infection. The drug is remarkably nontoxic and adverse effects are mild. Tenofovir is a nucleoside reverse transcriptase inhibitor and anti-HIV drug that competitively inhibits reverse transcriptase and causes chain termination after incorporation into DNA. Adverse side effects include gastrointestinal distress, asthenia, and headache but not anemia, leukopenia, or thrombocytopenia.

The chemical type of an antiviral compound is often important in determining its potential mechanisms and, therefore, its utility against specific types of viruses. Interferon is a glycoprotein produced by many types of mammalian cells. It stimulates host mechanisms to prevent viral penetration and also inhibits viral protein synthesis. Idoxuridine, as its name implies, is a pyrimidine, which inhibits viral DNA polymerase. Zidovudine and zalcitabine are also pyrimidines, but they inhibit reverse transcriptase and act as chain terminators. Only acyclovir is a purine that requires viral thymidine kinase to be converted to an active phosphorylated form, which then inhibits viral DNA polymerase.

Suramin must be administered intravenously and should be used cautiously in patients with kidney disease. It inhibits protein kinases and dihydrofolate reductase and reduces ATP synthesis. It is used in the treatment of certain extra-intestinal nematodes and is probably one of the most toxic anthelminthic agents.

 The other choices are incorrect. Diethylcarbamazine is rapidly absorbed following oral administration and increases the susceptibility of extra-intestinal nematodes to host antibodies. Ivermectin is used to treat O. volvulus in humans and is rapidly absorbed following oral administration. The primary use of praziquantel, which is rapidly absorbed orally, is in the treatment of infection from flat worms and flukes where it reduces the resistance of the parasite to host immune mechanisms. Zidovudine is also administered orally, but is used for treatment of AIDS, where most of its toxic symptoms are hematologic.

Leprosy is of two types namely lepromatous and tuberculoid.This patient is suffering from lepromatous leprosy on account of the symmetric nerve involvement, the abundant acid fast bacilli and the negative lepromin test. The course of this subtype is progressive and malignant. In case of tuberculoid leprosy the course is more benign with cellular immunity remaining intact. The skin biopsy shows few bacilli and there is a positive skin test. Combination therapy is recommended for all types of leprosy to avoid the emergence of resistance. Cases of lepromatous leprosy are treated with a combination therapy involving the use of the following:

• Dapsone
• Rifampin
• Clofazimine

This combination is given for 2 to 3 years, ideally till the skin biopsies are negative. Cases of indeterminate (borderline) and tuberculoid leprosy are treated with a combination therapy involving the use of the following:

• Dapsone
• Rifampin 

Rifampin for 6 to 12 months followed by dapsone—alone—for 2 years.

Foscarent can cause damage to the kidneys. To reduce the damaging effect, the patient may be put on intravenous fluids.

Acyclovir is a guanosine analog, which works by inhibiting viral DNA polymerase. This slows down the rate at which viruses can replicate. Acyclovir is used primarily in the treatment of herpes simplex viruses 1 and 2, chickenpox, and shingles.

Allopurinol is a purine analog and xanthine oxidase inhibitor used in the treatment of chronic gout. 

Alendronic acid (trade name Fosamax) is a bisphosphonate used in the treatment of osteoporosis. Bisphosphonates reduce bone loss by encouraging apoptosis in osteoclasts.

Infliximab is a tumor necrosis factor-alpha (TNF-alpha) blocker used in the treatment of rheumatoid arthritis and several other autoimmune conditions. Sitagliptin (trade name Januvia) is a diabetes medication. Budesonide/formoterol (trade name Symbicort) is a combination long acting beta agonist and corticosteroid used in the treatment of asthma.

The nurse should instruct a patient on Allopurinol to drink 3000 mL of fluid a day to reduce the risk of kidney stone formation.