The correct answer is "Do not consume alcohol while taking this medication." 

In this question, what is really being tested is your knowledge of side effects/interactions with metronidazole. One of the major interactions to be aware of with metronidazole is that it can cause an unpleasant interaction when consumed with alcohol that is very similar to the symptoms that occur when one consumes alcohol while taking the alcohol deterrent, Antabuse. This reaction includes severe abdominal pain/cramping, nausea, vomiting, facial flushing, and headaches. Patients should avoid drinking alcohol while taking metronidazole and for three days after completing their course.

Eating spinach, lying flat for 30 minutes after taking metronidazole, taking cholesterol medication while taking metronidazole, and operating heavy machinery while taking metronidazole are inappropriate recommendations, as there are no known direct associations between metronidazole and spinach consumption, head elevation, cholesterol medications, or level of consciousness. 

B12 deficiency is common in patients on metformin, and should be monitored and supplemented either sublingually or intramuscularly.

The ringing in the ear is tinnitus, which is indicative of ototoxicity. Nausea, metallic taste in mouth, difficulty swallowing and skin reactions are not associated with the development of ototoxicity. 

All of these are potential side effects of ACE (angiotensin-converting enzyme) inhibitors such as enalapril, but angioedema (the swelling of the face, lips, and/or tongue) is a potentially life threatening condition, as swelling can obstruct the airway.

Nausea, vomiting, and diarrhea are common symptoms of digoxin toxicity. Other symptoms may include confusion, anorexia, irregular heartbeat, and palpitations. Tremors, mood swings, and rash are not generally seen with digoxin toxicity. 

Meperidine is contraindicated because in high doses it can form a toxic metabolite that can lead to seizures. All other drugs listed are appropriate for pain control for sickle cell crisis. 

Extrapyramidal side effects generally present as slow or repetitive motions or postures (dystonia), spasm, tremor, slurred speech, slowed thought process, restlessness and anxiety, paranoia, and general overall distress. These effects are caused by antipsychotic drugs that act as dopamine D2 receptor antagonists.

Extrapyramidal side effects are common with typical antipsychotic drugs that act as dopamine D2 receptor antagonists. These include many selective serotonin reuptake inhibitors (SSRI's), serotonin–norepinephrine reuptake inhibitors (SNRI's), and norepinephrine–dopamine reuptake inhibitors (NDRI's), as well as antiemetics such as metclopramide.

Alprazolam is a benzodiazepine and is not associated with extrapyramidal adverse effects.

Chlorpropamide, an antidiabetic medication in the sulfonylurea class, has been associated with drug-induced SIADH (syndrome of inappropriate antidiuretic hormone secretion). This is a rare but serious complication that will generally resolve once drug treatment has stopped. None of the other drugs listed are associated with this side effect. 

Of the drugs listed, the only one associated with this bizarre side effect is rifampicin, a broad spectrum antibiotic used in tuberculosis. Urine, sweat, saliva, or tears may be turned any shade from red to reddish orange.