A 64-year-old man with schizophrenia is being treated for cirrhotic liver. Unfortunately, he develops a relapse of psychotic symptoms and needs a change in his antipsychotic prescription.
The safest option with regard to his hepatic status is:
A. Most psychotropic medications undergo hepatic metabolism. Notable exceptions are amisulpride, paliperidone, lithium, acamprosate, and gabapentin. These medications are largely renally excreted without much hepatic degradation. Hence in patients with hepatic failure, the antipsychotic of choice from the given list is amisulpride. Note that certain benzodiazepines, such as oxazepam, undergo glucuronide conjugation (phase 2 metabolism) reaction but no oxidation (phase 1 metabolism) in the liver. Oxazepam can be used in treating alcohol withdrawal in a patient with significantly low hepatic reserve.
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The mechanism of action of St John’s wort is:
D. St John’s wort has been shown to be an effective antidepressant in mild to moderate cases. It increases photosensitivity of skin but other adverse effects are limited. It is thought to act by inhibiting reuptake of multiple monoamines, including serotonin, norepinephrine, and dopamine. It also inhibits GABA and glutamate reuptake but the effects of these are unknown. It is a potent inducer of hepatic CYP450 enzymes, leading to a fall in plasma levels of carbamazepine, oral contraceptives, and warfarin if coprescribed.
Which one of the following acts via opiate receptors and could be a potential agent to prevent relapse of alcohol use?
D. Opioid receptor antagonists are tested as adjuncts for the treatment of alcohol dependence. They can reduce alcohol craving and alcohol consumption. If naltrexone is used in maintaining abstinence, the number of relapses is reduced and the severity of relapses, if they occur, is considerably less. Naloxone is a parenterally administered opioid antagonist, used to reverse the effects of exogenously administered opioids. Acamprosate, bupropion, and disulfiram do not act via an opioid mechanism.
A 44-year-old man with bipolar disorder treated with lithium develops chronic back pain. His GP wants to prescribe a NSAID analgesic and asks you to choose a NSAID with the least potential to interact with lithium. You will choose :
C. Aspirin (and sulindac, to some extent) has comparatively lesser potential to interact with lithium compared to most other NSAIDs. NSAIDs can reduce renal lithium clearance via their effects on fluid balance. This can lead to renal toxicity if the coadministration is sufficiently long. Indometacin is suspected to be worse compared to other NSAIDs in this regard, though careful monitoring of lithium levels is warranted even with use of COX-2 inhibitors such as rofecoxib. Lithium excretion is decreased by medications such as thiazides, angiotensin-converting enzyme inhibitors, and, to a lesser extent, frusemide (furosemide). Lithium clearance is increased by other medications with diuretic effects such as acetazolamide, mannitol, and caffeine.
Stimulants are useful in ADHD. The symptom that best responds to stimulants is:
B. Stimulants such as methylphenidate are more effective in treating hyperactivity than inattention due to ADHD. Methylphenidate is available in two forms—immediate release and sustained release forms. The immediate release form starts to act within 20 to 60 minutes after administration and acts for up to 2 to 4 hours, while the sustained release form acts up to 12 hours, obviating the need for divided doses.
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