Question-10: An elderly male aged 74 years was brought to the hospital since he had not passed urine for the past 24 hours and had severe pain in lower abdomen. on examination there was a bulge in the pubic region due to full urinary bladder. On catheterization, he passed 1.5 L urine and the pain was relieved. The patient gave the history of having difficulty in passing urine, poor stream, frequent urge to urinate and post-void dribbling for the last 3 years. Over the past few days he had been experiencing episodes of vertigo for which he was prescribed a medicine that he was taking for 2 days. Examination of the prescription revelaed that he was taking tab. Dimenhydrinate 50 mg 3 times daily.
(a) Could there be any relationship between the anti-vertigo medication and the episode of acute urinary retention?
Solution: Dimenhydrinate is a H1 antihistaminic-antivertigo drug with potent antimuscarinic action. Since muscarinic cholinoreceptors mediate neurogenic contraction of the detrusor muscle, antimuscarinic drugs interfere with vesical contractions needed for urination. Elderly men with benign hypertrophy of prostate have bladder neck obstruction and prone to develop urinary retention as a side effect of antimuscarinic drugs. This patient has history indicative of prostatic hypertrophy. As such, all drugs having antimuscarinic activity must be given cautiously to elderly males.
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Question-11: A lady aged 55 years presented for eye checkup. She has been having visual difficulty over the past few months, and lately she had started noticing 'halos' around the lights. She also has dull chronic ache in the forehead region. Tonometry revealed her intraocular pressure to be 22 and 44 mm Hg respectively in the left and right eye.
(a) Which mydriatic will be suitable for dilating her pupil for fundus examination and why?
Solution: The symptoms and intraocular pressure of this patient indicate that she is having glaucoma in both eyes. Phenylephrine (10%) eyedrop would be the suitable mydriatic for her. Phenylephrine is an alpha-1 adrenergic agonist that dilates the pupil by increasing the tone of radial muscles of iris, which are adrenergically innervated. It does not produce cycloplegia because the ciliary muscles lack adrenergic motor innervation. Cyclopegia causes blurring of near vision and is not required in this patient. Pheneylephrine is not likely to raise i.o.p. in galucoma patients. On the other hand, antimuscarinic mydriatics like tropicamide, cyclopentolate, etc. produce both mydriasis and cycloplegia, and tend to raise i.o.p. in glaucoma patients. Therefore, antimuscarinic are to be avoided in glaucoma patients.
Question-12: A 70-year-male presented with the complaints of weak stream of urine, sense of incomplete bladder voiding, urinary frequency and nocturia. After physical examination and ultrasound, he was diagnosed to have developed bening prostatic hypertrophy and was prescribed: Tab. Terazosin 5 mg, one tab daily at bed time. The patient took the medicine as advised and went off to sleep. At night, when he got up to pass urine, he felt giddy and fainted. On being laid flat on the bed, he regained consciousness within 2 minutes. Later, he was gradually propped up on the bed to the sitting position and then got up slowly and walked without any problem.
(a) What is the rationale of prescribing terazosin to this patient?
(b) What is the likely explanation for the fainting attack?
(c) What precautions could have avoided the fainting episode?
Solution (a) The smooth muscles of the bladder neck and prostatic urehtra are constricted by sympathetic innervation via alpha-1 adrenergic receptors. Terazosin being alpha-1 receptor blocker reduces the dynamic component of urinary obstruction in benign prostatic hypertrophy, improves urinary flow and affords symptomatic relief.
(b) The alpha-1 adrenergic receptors also mediate reflex vasoconstriction in the lower extremity and trunk which occurs on standing up from a reclining position to maintain cerebral blood flow. Terazosin blocked these alpha-1 recetors as well; reflex vasoconstriction failed to occur when this patient got up from bed to pass urine; blood supply to brain suffered and the patient fainted. That is why he soon regained consciousness on being laid flat on the bed. Such an event is especially likely to occur after the first dose when compensatory hemodynamic adjustments have not taken effect.
(c) The patient should have been advised not to spring up from the bed. He should first sit on the bed for few minutes and then slowly assume the erect posture. This would allow time for the reflex adjustments.
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(a) Could there be any relationship between the anti-vertigo medication and the episode of acute urinary retention?
Solution: Dimenhydrinate is a H1 antihistaminic-antivertigo drug with potent antimuscarinic action. Since muscarinic cholinoreceptors mediate neurogenic contraction of the detrusor muscle, antimuscarinic drugs interfere with vesical contractions needed for urination. Elderly men with benign hypertrophy of prostate have bladder neck obstruction and prone to develop urinary retention as a side effect of antimuscarinic drugs. This patient has history indicative of prostatic hypertrophy. As such, all drugs having antimuscarinic activity must be given cautiously to elderly males.
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Question-11: A lady aged 55 years presented for eye checkup. She has been having visual difficulty over the past few months, and lately she had started noticing 'halos' around the lights. She also has dull chronic ache in the forehead region. Tonometry revealed her intraocular pressure to be 22 and 44 mm Hg respectively in the left and right eye.
(a) Which mydriatic will be suitable for dilating her pupil for fundus examination and why?
Solution: The symptoms and intraocular pressure of this patient indicate that she is having glaucoma in both eyes. Phenylephrine (10%) eyedrop would be the suitable mydriatic for her. Phenylephrine is an alpha-1 adrenergic agonist that dilates the pupil by increasing the tone of radial muscles of iris, which are adrenergically innervated. It does not produce cycloplegia because the ciliary muscles lack adrenergic motor innervation. Cyclopegia causes blurring of near vision and is not required in this patient. Pheneylephrine is not likely to raise i.o.p. in galucoma patients. On the other hand, antimuscarinic mydriatics like tropicamide, cyclopentolate, etc. produce both mydriasis and cycloplegia, and tend to raise i.o.p. in glaucoma patients. Therefore, antimuscarinic are to be avoided in glaucoma patients.
Question-12: A 70-year-male presented with the complaints of weak stream of urine, sense of incomplete bladder voiding, urinary frequency and nocturia. After physical examination and ultrasound, he was diagnosed to have developed bening prostatic hypertrophy and was prescribed: Tab. Terazosin 5 mg, one tab daily at bed time. The patient took the medicine as advised and went off to sleep. At night, when he got up to pass urine, he felt giddy and fainted. On being laid flat on the bed, he regained consciousness within 2 minutes. Later, he was gradually propped up on the bed to the sitting position and then got up slowly and walked without any problem.
(a) What is the rationale of prescribing terazosin to this patient?
(b) What is the likely explanation for the fainting attack?
(c) What precautions could have avoided the fainting episode?
Solution (a) The smooth muscles of the bladder neck and prostatic urehtra are constricted by sympathetic innervation via alpha-1 adrenergic receptors. Terazosin being alpha-1 receptor blocker reduces the dynamic component of urinary obstruction in benign prostatic hypertrophy, improves urinary flow and affords symptomatic relief.
(b) The alpha-1 adrenergic receptors also mediate reflex vasoconstriction in the lower extremity and trunk which occurs on standing up from a reclining position to maintain cerebral blood flow. Terazosin blocked these alpha-1 recetors as well; reflex vasoconstriction failed to occur when this patient got up from bed to pass urine; blood supply to brain suffered and the patient fainted. That is why he soon regained consciousness on being laid flat on the bed. Such an event is especially likely to occur after the first dose when compensatory hemodynamic adjustments have not taken effect.
(c) The patient should have been advised not to spring up from the bed. He should first sit on the bed for few minutes and then slowly assume the erect posture. This would allow time for the reflex adjustments.
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