Drug reactions Flashcards
What drug reactions are common in Lewy body dementia
Severe akinesia, dystonias, neuroleptic malignant syndrome are common reactions to even very low doses of older typical antipsychotics.
What drugs are associated with serosal fibrosis syndrome and what is it?
“Cabergoline, pergolide, bromocriptine, and dihydroergocriptine are all ergot-derived dopamine agonists that
have been associated with serosal fibrosis syndromes. Ropinirole is a nonergoline and does not have this adverse
effect.”
fibrotic and serosal inflammatory disorders such as pleuritis, pleural effusion, pleural fibrosis, pulmonary fibrosis, pericarditis, pericardial effusion, cardiac valvulopathy or retroperitoneal fibrosis have occurred after prolonged usage of cabergoline.
What is midodrine used for? What are its side effects?
“Midodrine is a prodrug that is transformed in the liver to a potent agonist of alpha receptors in arteries and veins.
Given its predictable absorption and peak effect, it is the sympathomimetic of choice for treatment of
neurogenic orthostatic hypotension. One common side effect is scalp pruritus, a manifestation of alpha
adrenergic mediated piloerection. Its most potentially serious side effect is supine hypertension. Midodrine
should not be administered late in the evening and patients taking the drug should avoid lying flat.”
Why use Carbidopa? What dose of carbidopa is required for saturation of enzymes? SE of lower dose
“Carbidopa inhibits the enzyme L-aromatic amino acid decarboxylase (also known as dopa decarboxylase) and does not cross the blood-brain barrier. It does prevent the peripheral conversion of levodopa to dopamine.
Addition of carbidopa to levodopa results in less formation of dopamine outside the blood-brain barrier,
significantly decreasing the likelihood of nausea, vomiting, and orthostatic hypotension. This also improves delivery into the CNS for increased potency in control of tremor, bradykinesia, and rigidity but also increasing the likelihood of central side effects such as hallucinations and dyskinesias. In addition, the peripheral decarboxylase system requires 75 mg/d to 200 mg/d carbidopa. Reducing the carbidopa would be expected to decrease dopamine availability in the brain and thus decrease the likelihood of hallucinations.”
“Suboptimal doses of carbidopa are a frequent cause of nausea/vomiting at the initiation of levodopa therapy. It
takes 100 mg to 150 mg of carbidopa per day to saturate the peripheral aromatic aminoacid decarboxylase
enzyme to prevent peripheral side effects of levodopa. Promethaziine and metaclopramide block dopamine
receptors and may worsen the parkinsonism.”
What is the rate limiting step in the biosynthesis of catecholamine neurotransmitters?
“The hydroxylation of tyrosine by the enzyme tyrosine hydroxylase is the rate-limiting step in the biosynthesis of the catecholamine neurotransmitters dopamine, norepinephrine, and epinephrine.”
