Interacting drugs- summary

+ Colistimethate Sodium

  Aminoglycosides

 concurrent use increase the risk of respiratory paralysis and renal dysfunction

Cephalothin

 The nephrotoxic effects of colistimethate increased by cephalothin. Monitor renal function

 Colisthimethate +

 Non deplorizing muscle relaxant

neuromuscular blockade enhanced 

Gram-negative bacilli

Repiratory arrest, decreased urine output or increased BUN or serum creatinine,

paresthesia, tingling of the extremities or the tongue, generalised itching, or urticaria, drug fever,

GI upset, vertigo, slurring of speech, The subjective symptoms reported by the adult may not be manifested in infants or young children, thus requiring close attention to renal function.

Hypersensitivity to colistimethate sodium, infections due to Proteus or Neiseria species.

Special precautions;

Respiratory effects- Respiratory arrest has occured following IM administration.

Impaired renal function increases the posibility of apnea and neuromuscular blockade, generally because of failure to follow recommended guidelines, overdosage failure to reduce dose commensurate with degree of renal impairment or concomittant use of other anibiotics or drugs with neuromuscular blocking potentail.

If apnea occurs, treat with assisted respiration, oxygen and calcium chloride injections.

Nephrotoxicity- A decrase in urine uttput or increase in BUN or serum creatinine can be signs of nephrotoixicity, which is probably a dose-dependent effect. These manifestations are revesible following discontinuation.

Warnings

Maximum dosage- Do not exceed 5mg/kg/day in patients with normal renal function. Neurologic efects- may occur transiently. These include circumoral paresthesias or numbness, tingling of the extremities, generalized pruritus, vertigo, dizziness or slurring of speech.

Warn patients not to drive vehicles or use hazardous machinery while on therapy

Dosage reductions may alleviate symptoms.

Renal function impairment- Since colistimethate is mainly eliminated by renal excretion,use with caution when the possibility of impaired renal function exists.

Consider the decline in renal function with advanced age. When actual renal impairment is present, use colistimethate with extreme caution, reduce dosage in proprotion to the extent of impairment.

Pregnancy- Use only when clearly needed and when the potential benefits outweigh the potential hazards.

Indications

Treatment of chronic infections due to sensitive strains of gram-negative bacilli.

Dosage-

Adults and children- For IMor IVuse 2.5 to 5mg/kg/day in 2 or 4 divided doses for patients with normal renal function.

Missed dose-  1. If you miss a dose of this medicine, take it as soon as possible.

2. However, if it is almost time for next dose, skip the missed dose and go back to your regular dosing schedule.

3. Do not double doses.

Pharmacokinetics

Higher initial blood levels are obtained following IV administration.

Blood levels peak between 5 and 10 mcg/ml beteen 2 and 3 hours after IM administration. Serum half life is 2 to 3 hours.

Pregnancy-

Use only when clearly needed and when the potential benefits outweigh the potential hazards.