Side Effect "Antidotes" Flashcards
amantadine (Symmetrel)
Indication: Drug-Induced EPS; Parkinson’s Disease; Influenza A (though avoid per CDC due to resistance)
Dose: Start 100mg BID; MAX=300mg/d
(ER): 137mg QHS; increase after 1wk to 374mg QHS (max) (use with PD patients taking Levodopa (but costs $30k/yr) (brand name: Gocovri)
Monitoring: None required
Mechanism: weak NMDA antagonist; potentiates dopaminergic neurons; antiviral
Advantages: fewer anticholinergic effects; minimal drug interactions; better for elderly
Disadvantages: may worsen psychosis because of dopaminergic effects (not usual); requires renal adjustments
ADEs: nausea; dizziness; orthostatic hypotension; insomnia; blurred vision; constipation; dry mouth; (rare): intense urges to gamble/spend money (or sex)
Off-Label: ADHD; enuresis; T-R Depression; OCD
benztropine (Cogentin)
Indication: Drug-Induced EPS; Parkinson’s Disease
Dose: Start 1mg BID; MAX=3mg/d (acute 1-2mg IM)
Monitoring: None required.
Mechanism: anticholinergic; antihistaminergic
Advantages: No clinically significant drug reactions
Disadvantages: avoid with other anticholinergic agents
ADEs: avoid in acute-closure glaucoma (!!); dry mouth; constipation; urinary retention; sedation; confusion and delirium (esp. in elderly)
Off-Label: sialorrhea (excessive salivation); hyperhidrosis (excessive sweating); priapism (in stallions – vet work)
deutetrabenazine (Austedo)
Indication: Tardive Dyskinesia (TD); Huntington’s Chorea
Dose: Start 6mg BID with food; Increase weekly by 6mg/d; MAX = 48mg/d
Monitoring: EKG (especially with cardiac disease)
Mechanism: reversible inhibitor of vesicular monoamine transporter 2 (VMAT-2). This prevents VMAT2 from transporting dopamine back into the neuron so that it remains in the synaptic space and is vulnerable to metabolism, leading to there being less dopamine in the space (TD likely due to hypersensitivity to dopamine)
Advantages: None; consider generic tetrabenazine (which has suicidality ADE) [deuterated means that hydrogens are replaced by deuterium, slowing metabolism and increasing half-life]
Disadvantages: $70k/yr; potential suicidality; (consider tetrabenazine)
ADEs: sedation; somnolence; diarrhea; prolonged QTc (watch in electrolyte disturbances, poor metabolizers, and 2D6 inhibitors); potential suicidality
Off-Label: Tourette’s; Tic Disorders
metformin (Glucophage)
Indication: Diabetes mellitus, type 2; CONTRAINDICATED - >75yo, organ failure
Dose: Start 500mg BID; increase by 500mg weekly; MAX=2250mg/d
(ER): Start 500mg QPM; increase by 500mg weekly to 1000mg BID (preferred)
Monitoring: EGFR; Blood glucose; weight; abdominal circumference; lipids; A1c; B12 (annual – if low, oral supplementation will not correct and you will need IM); consider Ca supplementation if diet low; diet and exercise (!!); AVOID ALCOHOL (!!)
Mechanism: decreases glucose production by the liver; increases insulin sensitivity
Advantages: More weight loss (avg=7 lbs) and BMI than placebo; improved lipids and insulin resistance with patients on antipsychotics; best for: recently started on antipsychotic, overweight, but BMI<33, younger, rapid weight gain
Disadvantages: None particularly
ADEs: diarrhea; nausea; abdominal bloating; flatulence; rare cases of lactic acidosis
Off-Label: Weight management for patients on antipsychotics; polycystic ovary syndrome; prediabetes; female infertility
trihexyphenidyl (Artane)
Indication: Drug-Induced EPS; Parkinson’s Disease
Dose: Start at 2mg daily; increase by 2mg/d every 3-5d; MAX = 5mg TID
Monitoring: None required.
Mechanism: Anticholinergic; Antihistaminergic
Advantages: None particularly
Disadvantages: possibility of recreational use (Iraqi soldiers to help with combat stress; substitute for LSD; Oliver Sacks hallucinated an entire conversation with friends)
ADEs: avoid in acute-closure glaucoma (!!); dry mouth; constipation; urinary retention; sedation; confusion and delirium (esp. in elderly)
Off-Label: sialorrhea (excessive salivation); hyperhidrosis (excessive sweating)
valbenazine (Ingrezza)
Indication: Tardive Dyskinesia
Dose: Start 40mg daily; increase after one week to 80mg
Monitoring: EKG (especially with cardiac disease)
Mechanism: reversible inhibitor of vesicular monoamine transporter 2 (VMAT-2). This prevents VMAT2 from transporting dopamine back into the neuron so that it remains in the synaptic space and is vulnerable to metabolism, leading to there being less dopamine in the space (TD likely due to hypersensitivity to dopamine)
Advantages: 40% response rate (50% improvement in TD)
Disadvantages: $70k/yr; potential suicidality (consider tetrabenazine)
ADEs: sedation; somnolence; akathisia; prolonged QTc (watch in electrolyte disturbances, poor metabolizers, and 2D6 inhibitors); potential suicidality
Off-Label: Tourette’s; Tic Disorders
cyproheptadine (Periactin)
Indication: allergic rhinitis; urticaria; most commonly used appetite stimulant in cats
Dose: 4mg-12mg between one to two (1-2) hours before sexual activity.
Monitoring: None required.
Mechanism: H1 receptor antagonist with mild anti-serotonergic effects
ADEs: sedation; reversal of antidepressant therapeutic effects; confusion; weight gain; anticholinergic effects
Off-Label: antidepressant-induced sexual dysfunction (works best with anorgasmia (mean dose 8.6mg); appetite stimulant (therefore anorexia and bulimia); acute management of serotonin syndrome; counteract excessive sweating in SRIs; counteract vivid dreams in SRIs
