An HIV-positive patient is hospitalized for evaluation of symptoms of progressive weakness, dyspnea, weight loss, and low-grade fever. A biopsy of lung tissue reveals Pneumocystis carinii pneumonia. This diagnosis means that the patient

Choice A reason:
Morphine is not most effective when given orally due to the high first-pass effect. The first-pass effect refers to the metabolism of a drug in the liver immediately after it enters the bloodstream from the gastrointestinal tract, significantly reducing the amount of active drug that reaches systemic circulation. Therefore, oral administration of morphine is not the most effective route because much of it is metabolized before it can exert its effect.

Choice B reason:
Morphine will be more effective when given via a non-enteral route such as intravenous (IV) or subcutaneous (SQ) because these routes bypass the liver, thereby avoiding the first-pass metabolism. This allows a higher concentration of the active drug to reach the systemic circulation, providing a more potent and effective pain relief.

Choice C reason:
Oral and IV administration of morphine do not have the same effect due to the first-pass metabolism. When morphine is administered orally, a significant amount is metabolized by the liver before it reaches the systemic circulation, whereas IV administration delivers the drug directly into the bloodstream, bypassing the liver and allowing a higher active concentration.

Choice D reason:
Morphine is not primarily excreted by the lungs; it is mainly metabolized by the liver and excreted by the kidneys. This statement does not accurately demonstrate an understanding of the first-pass effect or the pharmacokinetics of morphine.

Choice A reason:
While decreased cerebral blood flow can contribute to various neurological conditions, it is not the primary cause of hepatic encephalopathy. Hepatic encephalopathy is primarily associated with liver dysfunction rather than cerebrovascular issues. Thus, this choice is incorrect.
Choice B reason:
Impaired ammonia metabolism is the primary cause of hepatic encephalopathy. When the liver is unable to adequately convert ammonia to urea due to chronic liver disease, ammonia accumulates in the bloodstream. This leads to toxic effects on the brain, resulting in the symptoms of hepatic encephalopathy. Therefore, this choice accurately reflects the underlying pathophysiology of the condition.
Choice C reason:
Hyperbilirubinemia and jaundice are common in liver disease but are not the primary causes of hepatic encephalopathy. These conditions result from impaired bilirubin metabolism and do not directly lead to the neurological manifestations seen in hepatic encephalopathy. Therefore, this choice is incorrect.
Choice D reason:
Fluid and electrolyte imbalances can occur with chronic liver disease but are not the primary cause of hepatic encephalopathy. While they may exacerbate the condition, the main issue is the accumulation of ammonia due to impaired liver function. Hence, this choice is incorrect.