OzEMedicine - Wiki for Australian Emergency Medicine Doctors

see also: beta adrenergic blockers

• 10, 40, 160mg dark pink tabs; 1mg/ml 1ml ampoule;
• Racemic mixture 1:1 ratio - only (-) enantiomer active;

• Highly lipophilic, almost completely absorbed orally, but 1st pass → only 25% (dose dependant as ? saturable 1st pass) reaches syst.circul.;

• Vd=4L/kg; Readily enters CNS; 90% bound to plasma proteins;
• Some taken up in symp.N endings & released upon stimulation;

• Blocks beta1 & beta2 equally, no intrinsic symp. activity, no alpha-block:
  • decreased renin secretion;
  • bradycardia & negative inotropic effect ⇒ decreased cardiac output;
  • decreased BP if hypertension but full response may take several weeks:
    • (initial increase in peripheral resistance (beta2 block) which later normalises, then falls)
  • suppress exercise-induced tachycardia if therapeutic dose;
  • block catecholamine-induced tremor;
  • class 2 antiarrhythmic actions:
    • decreases spontaneous rate of depolarisation of ectopic pacemakers;
    • decreases conduction in atria & in AV node;
    • increases functional refractory period of AV node;
      • NB. some membrane-stabilising effect (Class Ia) in high [];
    • decreases angina by decreased HR, decreased contractility ⇒ decreased oxygen needs;
    • increased exercise tolerance if exertional angina;
  • beta 2 blockade:
    • bronchospasm
    • blockage of skeletal muscle vasodilatation;
    • adverse lipid profile?;
    • impaired glucose mobilisation & K+ entry into cells;

• Extensive metabolised → metabolites → urine;
• T1/2=4hrs, but action lasts long enough for bd dose;

• bradycardia & hypotension even at small doses; adverse lipid profile;
• anorexia, nausea, vomiting, diarrhoea,abdo.pain; dizziness; vivid dreams; insomnia; psych.probs;
• bronchospasm; cold extremities; rarely skin/blood disorders;
• may ppt cardiac failure if: AMI, alcoholic cardiomyop., etc;
• abrupt withdrawal ⇒ inc. angina, AMI, ventricular arrhythmias;

• bradycardia; hypotension; CCF; bronchospasm;

• oral: 40mg bd → 160mg bd (max);
• IV: 1mg over 1min, repeat 2min prn (max: 10mg or 5mg if GA);

• unstable diabetes:
  • mask tachycardia response in hypoglycaemia;
  • decr. glucose mobilis. → delay recovery in hypoglyc.
  • (rarely impair insulin release);
• asthma
  • ⇒ potential life-threatening bronchoconstriction;
  • ⇒ block catecholamine inhib. of mast-cell degranulation;
• PVD, Raynaud's → vasoconst.→ inc. interm. claudication, esp. smoker;
• phaeochromocytoma - use alpha-blocker 1st to avoid uncompensated alpha vasoc.
• athletes
  • decr. exercise tolerance: decr. sk.muscle vasodil.;
  • decr. glucose & FFA mobilisation;
  • decr. cardiac response to exertion;
  • decr. beta induced exertional K shift into sk.muscle cells to buffer the efflux of K from normal exercising muscle cells
• CCF; or RVF due to pulm.HT; or signif. RVH; or cardiogenic shock;
• Bradycardia < 50/min; or 2/3 deg. AV block;
• Myocardial depressant anaesthetics (ether, chloroform, cyclopropane);
• Prolonged fasting;

• verapamil, diltiazem ⇒ AV block & decr. contractility!
• digoxin ⇒ AV block
• reserpine/guanethidine ⇒ XS decr. resting symp. tone;
• Class I antiarrhythmics (eg. disopyramide);
• clonidine - clonidine should not be stopped until several days after stopping propranolol.