Which of the following adverse effects most likely occurred in the patient who received a standard dose of morphine intramuscularly?

Correct Answer: B

Rationale: The correct answer is B: Impairment of far vision. Morphine is known to cause miosis, which is constriction of the pupil. This can lead to impaired far vision due to decreased ability to focus on distant objects. Dysphoria (A), diarrhea (C), and hypertension (D) are potential adverse effects of morphine, but impairment of far vision is more commonly associated with its use. Dysphoria is a mood-related adverse effect, diarrhea is a gastrointestinal adverse effect, and hypertension is a cardiovascular adverse effect, none of which directly relate to the effect on vision caused by morphine.

Correct Answer: C

Rationale: The correct answer is C: Cocaine. Cocaine is a stimulant drug that acts quickly to provide immediate relief due to its ability to increase alertness and energy levels. This can help alleviate symptoms rapidly. Phencyclidine (A) is a dissociative drug, not typically used for immediate relief. Cannabis (B) is not known for providing immediate relief and may have varying effects. Heroin (D) is an opioid that acts more slowly and is not typically used for immediate relief. Therefore, among the choices, cocaine is the most appropriate for immediate relief.

Correct Answer: A

Rationale: The correct answer is A: Heroin. Heroin is an opioid drug, and withdrawal symptoms typically include intense cravings, restlessness, muscle and bone pain, insomnia, vomiting, and other flu-like symptoms. The man most likely experienced withdrawal due to the physical and psychological dependence associated with heroin use. Cocaine, amphetamines, and LSD do not typically produce physical withdrawal symptoms like heroin.

Correct Answer: A

Rationale: The correct answer is A: Inhibition of transmitter reuptake at noradrenergic synapses. This mechanism of action is consistent with symptoms related to increased noradrenergic activity. By inhibiting reuptake, more neurotransmitter remains in the synaptic cleft, leading to increased stimulation of postsynaptic receptors. Options B, C, and D do not directly relate to the patient's signs and symptoms, which are likely due to excess noradrenergic activity. Option B, activation of opiate receptors, would not explain the symptoms. Option C, activation of serotonergic presynaptic receptors, is not relevant to noradrenergic activity. Option D, stimulation of monoamine release, is less likely as the symptoms are more indicative of increased noradrenaline levels due to reuptake inhibition.

Correct Answer: A

Rationale: The correct answer is A: Amyl nitrite. Amyl nitrite is known to cause methemoglobinemia, which can present as the syndrome described in the patient. Nitrous oxide, propane, and helium do not typically cause methemoglobinemia. Amyl nitrite acts as a vasodilator and can lead to the formation of methemoglobin, reducing the oxygen-carrying capacity of blood. Methemoglobinemia can manifest as cyanosis, headache, dizziness, fatigue, and shortness of breath. Nitrous oxide is an anesthetic gas that does not cause methemoglobinemia. Propane and helium are gases used for various purposes but are not associated with methemoglobinemia. Therefore, based on the patient's symptoms and the mechanism of action of the drugs listed, amyl nitrite is the most likely cause of the syndrome.